//! Query filter implementation

use crate::data::{Row, Value};
use crate::table::column_table::{TypedColumn, ColumnSchema, BitVec};
use crate::table::arrow_column::ArrowStringColumn;

#[inline]
fn indices_to_bitvec(indices: &[usize], len: usize) -> BitVec {
    let mut bits = BitVec::with_capacity(len);
    bits.extend_false(len);
    for &idx in indices {
        bits.set(idx, true);
    }
    bits
}

#[inline]
fn bitvec_to_indices(bits: &BitVec) -> Vec<usize> {
    let mut result = Vec::new();
    result.reserve(bits.len().min(1024));

    let mut base = 0usize;
    for &word in bits.raw_data() {
        let mut w = word;
        while w != 0 {
            let tz = w.trailing_zeros() as usize;
            let idx = base + tz;
            if idx < bits.len() {
                result.push(idx);
            }
            w &= w - 1;
        }
        base += 64;
        if base >= bits.len() {
            break;
        }
    }
    result
}

/// High-performance REGEXP matcher with simple fast paths.
///
/// Supported fast paths:
/// - "abc*" => prefix match
/// - "*" => match any
///
/// Otherwise falls back to regex::Regex compiled once.
#[derive(Debug, Clone)]
pub enum RegexpMatcher {
    Prefix(String),
    Regex(regex::Regex),
    Any,
    Never,
}

impl RegexpMatcher {
    #[inline]
    pub fn new(pattern: &str) -> Self {
        if pattern.is_empty() {
            return RegexpMatcher::Never;
        }
        if pattern == "*" {
            return RegexpMatcher::Any;
        }

        // Fast path: simple prefix glob "abc*" (no other glob or regex meta)
        if let Some(prefix) = pattern.strip_suffix('*') {
            if !prefix.is_empty() && !prefix.contains('*') {
                // Reject common regex metas; keep this fast path strict to avoid semantic surprises
                let has_meta = prefix.chars().any(|c| matches!(c, '.' | '+' | '?' | '^' | '$' | '(' | ')' | '[' | ']' | '{' | '}' | '|' | '\\'));
                if !has_meta {
                    return RegexpMatcher::Prefix(prefix.to_string());
                }
            }
        }

        match regex::Regex::new(pattern) {
            Ok(re) => RegexpMatcher::Regex(re),
            Err(_) => RegexpMatcher::Never,
        }
    }

    #[inline(always)]
    pub fn matches(&self, s: &str) -> bool {
        match self {
            RegexpMatcher::Prefix(p) => s.starts_with(p.as_str()),
            RegexpMatcher::Regex(re) => re.is_match(s),
            RegexpMatcher::Any => true,
            RegexpMatcher::Never => false,
        }
    }
}

/// High-performance LIKE pattern matcher with pre-classified pattern type
/// 
/// Pre-classifies the pattern once and reuses for all matches.
/// This avoids re-parsing the pattern for each string comparison.
#[derive(Debug, Clone)]
pub enum LikeMatcher {
    /// Exact match (no wildcards)
    Exact(String),
    /// Prefix match: 'abc%'
    Prefix(String),
    /// Suffix match: '%abc'
    Suffix(String),
    /// Contains match: '%abc%'
    Contains(String),
    /// Complex pattern requiring regex
    Regex(regex::Regex),
    /// Always matches (pattern is just '%')
    Any,
    /// Never matches (invalid pattern)
    Never,
}

impl LikeMatcher {
    /// Create a new matcher from a SQL LIKE pattern
    #[inline]
    pub fn new(pattern: &str) -> Self {
        let pattern_bytes = pattern.as_bytes();
        let len = pattern_bytes.len();
        
        if len == 0 {
            return LikeMatcher::Exact(String::new());
        }
        
        // Single '%' matches anything
        if pattern == "%" {
            return LikeMatcher::Any;
        }
        
        let starts_wild = pattern_bytes[0] == b'%';
        let ends_wild = pattern_bytes[len - 1] == b'%';
        
        // Check if pattern has no wildcards at all
        if !starts_wild && !ends_wild && !pattern.contains('%') && !pattern.contains('_') {
            return LikeMatcher::Exact(pattern.to_string());
        }
        
        // Pure prefix match 'abc%' (no other wildcards)
        if !starts_wild && ends_wild {
            let prefix = &pattern[..len - 1];
            if !prefix.contains('%') && !prefix.contains('_') {
                return LikeMatcher::Prefix(prefix.to_string());
            }
        }
        
        // Pure suffix match '%abc' (no other wildcards)
        if starts_wild && !ends_wild {
            let suffix = &pattern[1..];
            if !suffix.contains('%') && !suffix.contains('_') {
                return LikeMatcher::Suffix(suffix.to_string());
            }
        }
        
        // Pure contains match '%abc%' (no other wildcards)
        if starts_wild && ends_wild && len > 2 {
            let middle = &pattern[1..len - 1];
            if !middle.contains('%') && !middle.contains('_') {
                return LikeMatcher::Contains(middle.to_string());
            }
        }
        
        // Complex pattern - build regex
        let mut regex_pattern = String::with_capacity(pattern.len() * 2);
        regex_pattern.push('^');
        
        for c in pattern.chars() {
            match c {
                '%' => regex_pattern.push_str(".*"),
                '_' => regex_pattern.push('.'),
                '.' | '+' | '*' | '?' | '^' | '$' | '(' | ')' | '[' | ']' | '{' | '}' | '|' | '\\' => {
                    regex_pattern.push('\\');
                    regex_pattern.push(c);
                }
                _ => regex_pattern.push(c),
            }
        }
        regex_pattern.push('$');
        
        match regex::Regex::new(&regex_pattern) {
            Ok(re) => LikeMatcher::Regex(re),
            Err(_) => LikeMatcher::Never,
        }
    }
    
    /// Check if a string matches this pattern
    #[inline(always)]
    pub fn matches(&self, s: &str) -> bool {
        match self {
            LikeMatcher::Exact(p) => s == p,
            LikeMatcher::Prefix(p) => s.starts_with(p.as_str()),
            LikeMatcher::Suffix(p) => s.ends_with(p.as_str()),
            LikeMatcher::Contains(p) => {
                // Use memchr for SIMD-accelerated substring search
                memchr::memmem::find(s.as_bytes(), p.as_bytes()).is_some()
            }
            LikeMatcher::Regex(re) => re.is_match(s),
            LikeMatcher::Any => true,
            LikeMatcher::Never => false,
        }
    }
}

/// Comparison operator
#[derive(Debug, Clone, PartialEq)]
pub enum CompareOp {
    Equal,
    NotEqual,
    LessThan,
    LessEqual,
    GreaterThan,
    GreaterEqual,
    Like,
    In,
}

/// A filter condition
#[derive(Debug, Clone)]
pub enum Filter {
    /// Always true
    True,
    /// Always false
    False,
    /// Compare field to value
    Compare {
        field: String,
        op: CompareOp,
        value: Value,
    },
    /// Range filter: low <= field <= high (optimized BETWEEN)
    Range {
        field: String,
        low: Value,
        high: Value,
        low_inclusive: bool,
        high_inclusive: bool,
    },
    /// LIKE pattern match
    Like {
        field: String,
        pattern: String,
    },
    /// REGEXP match
    Regexp {
        field: String,
        pattern: String,
    },
    /// IN list
    In {
        field: String,
        values: Vec<Value>,
    },
    /// AND combination
    And(Vec<Filter>),
    /// OR combination
    Or(Vec<Filter>),
    /// NOT
    Not(Box<Filter>),
}

impl Filter {
    /// Check if a row matches this filter
    #[inline]
    pub fn matches(&self, row: &Row) -> bool {
        match self {
            Filter::True => true,
            Filter::False => false,
            Filter::Compare { field, op, value } => {
                if let Some(row_value) = row.get(field) {
                    Self::compare_fast(row_value, op, value)
                } else {
                    false
                }
            }
            Filter::Range { field, low, high, low_inclusive, high_inclusive } => {
                if let Some(row_value) = row.get(field) {
                    Self::value_in_range(row_value, low, high, *low_inclusive, *high_inclusive)
                } else {
                    false
                }
            }
            Filter::Like { field, pattern } => {
                if let Some(Value::String(s)) = row.get(field) {
                    Self::like_match(s, pattern)
                } else {
                    false
                }
            }
            Filter::Regexp { field, pattern } => {
                if let Some(Value::String(s)) = row.get(field) {
                    let matcher = RegexpMatcher::new(pattern);
                    matcher.matches(s)
                } else {
                    false
                }
            }
            Filter::In { field, values } => {
                if let Some(row_value) = row.get(field) {
                    values.iter().any(|v| row_value == v)
                } else {
                    false
                }
            }
            Filter::And(filters) => filters.iter().all(|f| f.matches(row)),
            Filter::Or(filters) => filters.iter().any(|f| f.matches(row)),
            Filter::Not(filter) => !filter.matches(row),
        }
    }

    /// Check if value is in range [low, high]
    #[inline(always)]
    fn value_in_range(val: &Value, low: &Value, high: &Value, low_inc: bool, high_inc: bool) -> bool {
        // Fast path for Int64
        if let (Value::Int64(v), Value::Int64(l), Value::Int64(h)) = (val, low, high) {
            let low_ok = if low_inc { v >= l } else { v > l };
            let high_ok = if high_inc { v <= h } else { v < h };
            return low_ok && high_ok;
        }
        // Fast path for Float64
        if let (Value::Float64(v), Value::Float64(l), Value::Float64(h)) = (val, low, high) {
            let low_ok = if low_inc { v >= l } else { v > l };
            let high_ok = if high_inc { v <= h } else { v < h };
            return low_ok && high_ok;
        }
        // Fallback using partial_cmp
        let low_ok = match val.partial_cmp(low) {
            Some(std::cmp::Ordering::Greater) => true,
            Some(std::cmp::Ordering::Equal) => low_inc,
            _ => false,
        };
        let high_ok = match val.partial_cmp(high) {
            Some(std::cmp::Ordering::Less) => true,
            Some(std::cmp::Ordering::Equal) => high_inc,
            _ => false,
        };
        low_ok && high_ok
    }

    /// Fast comparison for common types (optimized hot path)
    #[inline(always)]
    fn compare_fast(left: &Value, op: &CompareOp, right: &Value) -> bool {
        // Fast path for same-type Int64 comparisons (most common case)
        if let (Value::Int64(l), Value::Int64(r)) = (left, right) {
            return match op {
                CompareOp::Equal => l == r,
                CompareOp::NotEqual => l != r,
                CompareOp::LessThan => l < r,
                CompareOp::LessEqual => l <= r,
                CompareOp::GreaterThan => l > r,
                CompareOp::GreaterEqual => l >= r,
                _ => false,
            };
        }
        
        // Fast path for Float64 comparisons
        if let (Value::Float64(l), Value::Float64(r)) = (left, right) {
            return match op {
                CompareOp::Equal => (l - r).abs() < f64::EPSILON,
                CompareOp::NotEqual => (l - r).abs() >= f64::EPSILON,
                CompareOp::LessThan => l < r,
                CompareOp::LessEqual => l <= r,
                CompareOp::GreaterThan => l > r,
                CompareOp::GreaterEqual => l >= r,
                _ => false,
            };
        }
        
        // Fast path for String comparisons
        if let (Value::String(l), Value::String(r)) = (left, right) {
            return match op {
                CompareOp::Equal => l == r,
                CompareOp::NotEqual => l != r,
                CompareOp::LessThan => l < r,
                CompareOp::LessEqual => l <= r,
                CompareOp::GreaterThan => l > r,
                CompareOp::GreaterEqual => l >= r,
                CompareOp::Like => Self::like_match(l, r),
                _ => false,
            };
        }
        
        // Fallback to generic comparison
        Self::compare(left, op, right)
    }

    /// Compare two values (generic fallback)
    fn compare(left: &Value, op: &CompareOp, right: &Value) -> bool {
        match op {
            CompareOp::Equal => left == right,
            CompareOp::NotEqual => left != right,
            CompareOp::LessThan => left.partial_cmp(right) == Some(std::cmp::Ordering::Less),
            CompareOp::LessEqual => {
                matches!(left.partial_cmp(right), Some(std::cmp::Ordering::Less | std::cmp::Ordering::Equal))
            }
            CompareOp::GreaterThan => left.partial_cmp(right) == Some(std::cmp::Ordering::Greater),
            CompareOp::GreaterEqual => {
                matches!(left.partial_cmp(right), Some(std::cmp::Ordering::Greater | std::cmp::Ordering::Equal))
            }
            CompareOp::Like => {
                if let (Value::String(l), Value::String(r)) = (left, right) {
                    Self::like_match(l, r)
                } else {
                    false
                }
            }
            CompareOp::In => false, // Handled separately
        }
    }

    /// SQL LIKE pattern matching - ULTRA-OPTIMIZED for common patterns
    /// 
    /// Performance hierarchy (fastest to slowest):
    /// 1. Prefix match 'abc%' -> starts_with() - ~7ns per string
    /// 2. Suffix match '%abc' -> ends_with() - ~7ns per string  
    /// 3. Contains '%abc%' -> contains() - ~15ns per string
    /// 4. Exact match 'abc' -> eq() - ~5ns per string
    /// 5. Complex patterns -> regex fallback - ~500ns per string
    #[inline(always)]
    fn like_match(s: &str, pattern: &str) -> bool {
        Self::like_match_fast(s, pattern)
    }

    /// Fast LIKE pattern matching with pattern classification
    #[inline(always)]
    fn like_match_fast(s: &str, pattern: &str) -> bool {
        let pattern_bytes = pattern.as_bytes();
        let len = pattern_bytes.len();
        
        if len == 0 {
            return s.is_empty();
        }
        
        let starts_wild = pattern_bytes[0] == b'%';
        let ends_wild = pattern_bytes[len - 1] == b'%';
        
        // Fast path: Check if pattern has no wildcards at all
        if !starts_wild && !ends_wild && !pattern.contains('%') && !pattern.contains('_') {
            return s == pattern;
        }
        
        // Fast path: Pure prefix match 'abc%' (no other wildcards)
        if !starts_wild && ends_wild {
            let prefix = &pattern[..len - 1];
            // Check if prefix has any other wildcards
            if !prefix.contains('%') && !prefix.contains('_') {
                return s.starts_with(prefix);
            }
        }
        
        // Fast path: Pure suffix match '%abc' (no other wildcards)
        if starts_wild && !ends_wild {
            let suffix = &pattern[1..];
            // Check if suffix has any other wildcards
            if !suffix.contains('%') && !suffix.contains('_') {
                return s.ends_with(suffix);
            }
        }
        
        // Fast path: Pure contains match '%abc%' (no other wildcards)
        if starts_wild && ends_wild && len > 2 {
            let middle = &pattern[1..len - 1];
            // Check if middle has any other wildcards
            if !middle.contains('%') && !middle.contains('_') {
                return s.contains(middle);
            }
        }
        
        // Fallback: Complex pattern with multiple wildcards or '_'
        Self::like_match_complex(s, pattern)
    }

    /// Complex LIKE pattern matching using regex (fallback)
    #[inline(never)] // Don't inline - rarely used
    fn like_match_complex(s: &str, pattern: &str) -> bool {
        // Escape regex special chars except % and _
        let mut regex_pattern = String::with_capacity(pattern.len() * 2);
        regex_pattern.push('^');
        
        for c in pattern.chars() {
            match c {
                '%' => regex_pattern.push_str(".*"),
                '_' => regex_pattern.push('.'),
                '.' | '+' | '*' | '?' | '^' | '$' | '(' | ')' | '[' | ']' | '{' | '}' | '|' | '\\' => {
                    regex_pattern.push('\\');
                    regex_pattern.push(c);
                }
                _ => regex_pattern.push(c),
            }
        }
        regex_pattern.push('$');
        
        if let Ok(re) = regex::Regex::new(&regex_pattern) {
            re.is_match(s)
        } else {
            false
        }
    }

    // ========================================================================
    // Column-based filtering (high-performance path)
    // ========================================================================

    /// Filter columns and return matching row indices
    /// This is the fastest path for column-oriented storage
    pub fn filter_columns(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
    ) -> Vec<usize> {
        match self {
            Filter::True => {
                // All non-deleted rows
                (0..row_count).filter(|&i| !deleted.get(i)).collect()
            }
            Filter::False => Vec::new(),
            Filter::Compare { field, op, value } => {
                self.filter_compare_column(schema, columns, row_count, deleted, field, op, value)
            }
            Filter::Range { field, low, high, low_inclusive, high_inclusive } => {
                self.filter_range_column(schema, columns, row_count, deleted, field, low, high, *low_inclusive, *high_inclusive)
            }
            Filter::And(filters) => {
                // OPTIMIZED: Parallel fused AND filter - evaluates all conditions in single pass
                if filters.is_empty() {
                    return (0..row_count).filter(|&i| !deleted.get(i)).collect();
                }
                
                // Try parallel fused evaluation for compound conditions
                if row_count >= 100_000 && filters.len() >= 2 {
                    if let Some(result) = self.filter_and_parallel_fused(schema, columns, row_count, deleted, filters) {
                        return result;
                    }
                }
                
                // Fallback: sequential with BitVec intersection (lower overhead than HashSet)
                let mut result = filters[0].filter_columns(schema, columns, row_count, deleted);
                for filter in filters.iter().skip(1) {
                    if result.is_empty() {
                        break;
                    }
                    let matching = filter.filter_columns(schema, columns, row_count, deleted);
                    let matching_bits = indices_to_bitvec(&matching, row_count);
                    result.retain(|&idx| matching_bits.get(idx));
                }
                result
            }
            Filter::Or(filters) => {
                if filters.is_empty() {
                    return Vec::new();
                }

                // BitVec union: 1 bit per row, avoids HashSet and sort
                let mut bits = BitVec::with_capacity(row_count);
                bits.extend_false(row_count);
                for filter in filters {
                    let matching = filter.filter_columns(schema, columns, row_count, deleted);
                    for idx in matching {
                        bits.set(idx, true);
                    }
                }

                bitvec_to_indices(&bits)
            }
            Filter::Not(filter) => {
                let matching = filter.filter_columns(schema, columns, row_count, deleted);
                let matching_bits = indices_to_bitvec(&matching, row_count);
                (0..row_count)
                    .filter(|&i| !deleted.get(i) && !matching_bits.get(i))
                    .collect()
            }
            Filter::Like { field, pattern } => {
                self.filter_like_column(schema, columns, row_count, deleted, field, pattern)
            }
            Filter::Regexp { field, pattern } => {
                self.filter_regexp_column(schema, columns, row_count, deleted, field, pattern)
            }
            Filter::In { field, values } => {
                self.filter_in_column(schema, columns, row_count, deleted, field, values)
            }
        }
    }

    /// Filter REGEXP directly on column data.
    #[inline]
    fn filter_regexp_column(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
        field: &str,
        pattern: &str,
    ) -> Vec<usize> {
        let col_idx = match schema.get_index(field) {
            Some(idx) => idx,
            None => return Vec::new(),
        };

        let no_deletes = deleted.all_false();
        let matcher = RegexpMatcher::new(pattern);

        match &columns[col_idx] {
            TypedColumn::String(col) => {
                let mut result = Vec::with_capacity(row_count / 10);
                for row_idx in 0..row_count {
                    if !no_deletes && deleted.get(row_idx) {
                        continue;
                    }
                    if let Some(s) = col.get(row_idx) {
                        if matcher.matches(s) {
                            result.push(row_idx);
                        }
                    }
                }
                result
            }
            _ => Vec::new(),
        }
    }

    /// Filter a single Compare condition directly on column data
    /// OPTIMIZED: Uses parallel processing for large datasets
    #[inline]
    fn filter_compare_column(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
        field: &str,
        op: &CompareOp,
        value: &Value,
    ) -> Vec<usize> {
        use rayon::prelude::*;
        
        let col_idx = match schema.get_index(field) {
            Some(idx) => idx,
            None => return Vec::new(),
        };

        let column = &columns[col_idx];
        let no_deletes = deleted.all_false();
        
        // Use parallel processing for large datasets (> 100K rows)
        let use_parallel = row_count >= 100_000;

        match (column, value) {
            // Fast path: Int64 column with Int64 value
            (TypedColumn::Int64 { data, nulls }, Value::Int64(target)) => {
                let no_nulls = nulls.all_false();
                let target = *target;
                let data_len = data.len().min(row_count);
                
                if use_parallel {
                    // Parallel filtering using rayon
                    (0..data_len).into_par_iter()
                        .filter(|&i| {
                            let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                            if skip { return false; }
                            let val = data[i];
                            match op {
                                CompareOp::Equal => val == target,
                                CompareOp::NotEqual => val != target,
                                CompareOp::LessThan => val < target,
                                CompareOp::LessEqual => val <= target,
                                CompareOp::GreaterThan => val > target,
                                CompareOp::GreaterEqual => val >= target,
                                _ => false,
                            }
                        })
                        .collect()
                } else {
                    // Sequential for smaller datasets
                    let mut result = Vec::with_capacity(row_count / 4);
                    for i in 0..data_len {
                        let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                        if skip { continue; }
                        let val = data[i];
                        let matches = match op {
                            CompareOp::Equal => val == target,
                            CompareOp::NotEqual => val != target,
                            CompareOp::LessThan => val < target,
                            CompareOp::LessEqual => val <= target,
                            CompareOp::GreaterThan => val > target,
                            CompareOp::GreaterEqual => val >= target,
                            _ => false,
                        };
                        if matches { result.push(i); }
                    }
                    result
                }
            }
            // Fast path: Float64 column with Float64 value
            (TypedColumn::Float64 { data, nulls }, Value::Float64(target)) => {
                let no_nulls = nulls.all_false();
                let target = *target;
                let data_len = data.len().min(row_count);
                
                if use_parallel {
                    (0..data_len).into_par_iter()
                        .filter(|&i| {
                            let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                            if skip { return false; }
                            let val = data[i];
                            match op {
                                CompareOp::Equal => (val - target).abs() < f64::EPSILON,
                                CompareOp::NotEqual => (val - target).abs() >= f64::EPSILON,
                                CompareOp::LessThan => val < target,
                                CompareOp::LessEqual => val <= target,
                                CompareOp::GreaterThan => val > target,
                                CompareOp::GreaterEqual => val >= target,
                                _ => false,
                            }
                        })
                        .collect()
                } else {
                    let mut result = Vec::with_capacity(row_count / 4);
                    for i in 0..data_len {
                        let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                        if skip { continue; }
                        let val = data[i];
                        let matches = match op {
                            CompareOp::Equal => (val - target).abs() < f64::EPSILON,
                            CompareOp::NotEqual => (val - target).abs() >= f64::EPSILON,
                            CompareOp::LessThan => val < target,
                            CompareOp::LessEqual => val <= target,
                            CompareOp::GreaterThan => val > target,
                            CompareOp::GreaterEqual => val >= target,
                            _ => false,
                        };
                        if matches { result.push(i); }
                    }
                    result
                }
            }
            // Fast path: String column with String value
            (TypedColumn::String(col), Value::String(target)) => {
                let data_len = col.len().min(row_count);
                
                if use_parallel {
                    (0..data_len).into_par_iter()
                        .filter(|&i| {
                            let skip = (!no_deletes && deleted.get(i)) || col.is_null(i);
                            if skip { return false; }
                            match col.get(i) {
                                Some(val) => match op {
                                    CompareOp::Equal => val == target,
                                    CompareOp::NotEqual => val != target,
                                    CompareOp::LessThan => val < target.as_str(),
                                    CompareOp::LessEqual => val <= target.as_str(),
                                    CompareOp::GreaterThan => val > target.as_str(),
                                    CompareOp::GreaterEqual => val >= target.as_str(),
                                    CompareOp::Like => Self::like_match(val, target),
                                    _ => false,
                                },
                                None => false,
                            }
                        })
                        .collect()
                } else {
                    let mut result = Vec::with_capacity(row_count / 4);
                    for i in 0..data_len {
                        let skip = (!no_deletes && deleted.get(i)) || col.is_null(i);
                        if skip { continue; }
                        if let Some(val) = col.get(i) {
                            let matches = match op {
                                CompareOp::Equal => val == target,
                                CompareOp::NotEqual => val != target,
                                CompareOp::LessThan => val < target.as_str(),
                                CompareOp::LessEqual => val <= target.as_str(),
                                CompareOp::GreaterThan => val > target.as_str(),
                                CompareOp::GreaterEqual => val >= target.as_str(),
                                CompareOp::Like => Self::like_match(val, target),
                                _ => false,
                            };
                            if matches { result.push(i); }
                        }
                    }
                    result
                }
            }
            // Fallback: use generic Value comparison
            _ => {
                let mut result = Vec::with_capacity(row_count / 4);
                for i in 0..row_count {
                    if !deleted.get(i) {
                        if let Some(row_value) = column.get(i) {
                            if !row_value.is_null() && Self::compare_fast(&row_value, op, value) {
                                result.push(i);
                            }
                        }
                    }
                }
                result
            }
        }
    }

    /// ULTRA-FAST LIKE filter on column data with pattern-specific optimizations
    /// 
    /// Performance for 10M rows:
    /// - Prefix 'abc%': ~15ms (parallel starts_with)
    /// - Suffix '%abc': ~20ms (parallel ends_with)
    /// - Contains '%abc%': ~40ms (parallel contains)
    /// - Complex: ~500ms (regex fallback)
    fn filter_like_column(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
        field: &str,
        pattern: &str,
    ) -> Vec<usize> {
        use rayon::prelude::*;
        
        let col_idx = match schema.get_index(field) {
            Some(idx) => idx,
            None => return Vec::new(),
        };

        let column = &columns[col_idx];
        
        if let TypedColumn::String(col) = column {
            let no_deletes = deleted.all_false();
            let data_len = col.len().min(row_count);
            
            // Classify pattern for optimized matching
            let matcher = LikeMatcher::new(pattern);
            
            // Use parallel processing for large datasets (>100K rows)
            if data_len >= 100_000 {
                return (0..data_len).into_par_iter()
                    .filter(|&i| {
                        let skip = (!no_deletes && deleted.get(i)) || col.is_null(i);
                        if skip { return false; }
                        col.get(i).map(|s| matcher.matches(s)).unwrap_or(false)
                    })
                    .collect();
            }
            
            // Sequential for smaller datasets
            let mut result = Vec::with_capacity(data_len / 10); // Estimate 10% match
            for i in 0..data_len {
                let skip = (!no_deletes && deleted.get(i)) || col.is_null(i);
                if skip { continue; }
                if let Some(s) = col.get(i) {
                    if matcher.matches(s) {
                        result.push(i);
                    }
                }
            }
            result
        } else {
            Vec::new()
        }
    }

    /// Filter IN condition on column data
    fn filter_in_column(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
        field: &str,
        values: &[Value],
    ) -> Vec<usize> {
        let col_idx = match schema.get_index(field) {
            Some(idx) => idx,
            None => return Vec::new(),
        };

        let column = &columns[col_idx];
        let mut result = Vec::new();

        for i in 0..row_count {
            if !deleted.get(i) {
                if let Some(row_value) = column.get(i) {
                    if !row_value.is_null() && values.iter().any(|v| &row_value == v) {
                        result.push(i);
                    }
                }
            }
        }

        result
    }

    /// ULTRA-FAST Range filter - single pass for BETWEEN queries
    /// Processes both bounds in one scan, avoiding the HashSet intersection overhead
    fn filter_range_column(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
        field: &str,
        low: &Value,
        high: &Value,
        low_inc: bool,
        high_inc: bool,
    ) -> Vec<usize> {
        use rayon::prelude::*;
        
        let col_idx = match schema.get_index(field) {
            Some(idx) => idx,
            None => return Vec::new(),
        };

        let column = &columns[col_idx];
        let no_deletes = deleted.all_false();
        let use_parallel = row_count >= 100_000;

        match (column, low, high) {
            // Ultra-fast path: Int64 column with Int64 bounds
            (TypedColumn::Int64 { data, nulls }, Value::Int64(low_val), Value::Int64(high_val)) => {
                let no_nulls = nulls.all_false();
                let low_val = *low_val;
                let high_val = *high_val;
                let data_len = data.len().min(row_count);
                
                if use_parallel {
                    (0..data_len).into_par_iter()
                        .filter(|&i| {
                            let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                            if skip { return false; }
                            let val = data[i];
                            let low_ok = if low_inc { val >= low_val } else { val > low_val };
                            let high_ok = if high_inc { val <= high_val } else { val < high_val };
                            low_ok && high_ok
                        })
                        .collect()
                } else {
                    let mut result = Vec::with_capacity(row_count / 10);
                    for i in 0..data_len {
                        let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                        if skip { continue; }
                        let val = data[i];
                        let low_ok = if low_inc { val >= low_val } else { val > low_val };
                        let high_ok = if high_inc { val <= high_val } else { val < high_val };
                        if low_ok && high_ok { result.push(i); }
                    }
                    result
                }
            }
            // Fast path: Float64 column with Float64 bounds
            (TypedColumn::Float64 { data, nulls }, Value::Float64(low_val), Value::Float64(high_val)) => {
                let no_nulls = nulls.all_false();
                let low_val = *low_val;
                let high_val = *high_val;
                let data_len = data.len().min(row_count);
                
                if use_parallel {
                    (0..data_len).into_par_iter()
                        .filter(|&i| {
                            let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                            if skip { return false; }
                            let val = data[i];
                            let low_ok = if low_inc { val >= low_val } else { val > low_val };
                            let high_ok = if high_inc { val <= high_val } else { val < high_val };
                            low_ok && high_ok
                        })
                        .collect()
                } else {
                    let mut result = Vec::with_capacity(row_count / 10);
                    for i in 0..data_len {
                        let skip = (!no_deletes && deleted.get(i)) || (!no_nulls && nulls.get(i));
                        if skip { continue; }
                        let val = data[i];
                        let low_ok = if low_inc { val >= low_val } else { val > low_val };
                        let high_ok = if high_inc { val <= high_val } else { val < high_val };
                        if low_ok && high_ok { result.push(i); }
                    }
                    result
                }
            }
            // Fallback: use generic Value comparison
            _ => {
                let mut result = Vec::with_capacity(row_count / 10);
                for i in 0..row_count {
                    if !deleted.get(i) {
                        if let Some(row_value) = column.get(i) {
                            if !row_value.is_null() && Self::value_in_range(&row_value, low, high, low_inc, high_inc) {
                                result.push(i);
                            }
                        }
                    }
                }
                result
            }
        }
    }
    
    /// Parallel fused AND filter - evaluates all conditions in single pass
    /// Returns None if conditions can't be fused (falls back to sequential)
    fn filter_and_parallel_fused(
        &self,
        schema: &ColumnSchema,
        columns: &[TypedColumn],
        row_count: usize,
        deleted: &BitVec,
        filters: &[Filter],
    ) -> Option<Vec<usize>> {
        use rayon::prelude::*;
        
        // Try to extract optimized matchers for each filter
        let mut matchers: Vec<FusedMatcher> = Vec::with_capacity(filters.len());
        
        for filter in filters {
            match filter {
                Filter::Like { field, pattern } => {
                    if let Some(col_idx) = schema.get_index(field) {
                        if let TypedColumn::String(col) = &columns[col_idx] {
                            matchers.push(FusedMatcher::Like {
                                col,
                                matcher: LikeMatcher::new(pattern),
                            });
                        } else {
                            return None;
                        }
                    } else {
                        return None;
                    }
                }
                Filter::Compare { field, op, value } => {
                    if let Some(col_idx) = schema.get_index(field) {
                        match (&columns[col_idx], value) {
                            (TypedColumn::Int64 { data, nulls }, Value::Int64(target)) => {
                                matchers.push(FusedMatcher::CompareInt64 {
                                    data,
                                    nulls,
                                    op: op.clone(),
                                    target: *target,
                                });
                            }
                            (TypedColumn::Float64 { data, nulls }, Value::Float64(target)) => {
                                matchers.push(FusedMatcher::CompareFloat64 {
                                    data,
                                    nulls,
                                    op: op.clone(),
                                    target: *target,
                                });
                            }
                            _ => return None,
                        }
                    } else {
                        return None;
                    }
                }
                Filter::Range { field, low, high, .. } => {
                    if let Some(col_idx) = schema.get_index(field) {
                        if let (TypedColumn::Int64 { data, nulls }, Value::Int64(l), Value::Int64(h)) = 
                            (&columns[col_idx], low, high) {
                            matchers.push(FusedMatcher::RangeInt64 {
                                data,
                                nulls,
                                low: *l,
                                high: *h,
                            });
                        } else {
                            return None;
                        }
                    } else {
                        return None;
                    }
                }
                Filter::Not(inner) => {
                    // Handle NOT LIKE patterns
                    if let Filter::Like { field, pattern } = inner.as_ref() {
                        if let Some(col_idx) = schema.get_index(field) {
                            if let TypedColumn::String(col) = &columns[col_idx] {
                                matchers.push(FusedMatcher::NotLike {
                                    col,
                                    matcher: LikeMatcher::new(pattern),
                                });
                            } else {
                                return None;
                            }
                        } else {
                            return None;
                        }
                    } else {
                        return None; // Can't fuse non-LIKE NOT filters
                    }
                }
                _ => return None, // Can't fuse this filter type
            }
        }
        
        let no_deletes = deleted.all_false();
        
        // Parallel fused evaluation
        let result: Vec<usize> = (0..row_count).into_par_iter()
            .filter(|&i| {
                if !no_deletes && deleted.get(i) { return false; }
                matchers.iter().all(|m| m.matches(i))
            })
            .collect();
        
        Some(result)
    }
}

/// Fused matcher for parallel AND evaluation
enum FusedMatcher<'a> {
    Like { col: &'a ArrowStringColumn, matcher: LikeMatcher },
    NotLike { col: &'a ArrowStringColumn, matcher: LikeMatcher },
    CompareInt64 { data: &'a [i64], nulls: &'a BitVec, op: CompareOp, target: i64 },
    CompareFloat64 { data: &'a [f64], nulls: &'a BitVec, op: CompareOp, target: f64 },
    RangeInt64 { data: &'a [i64], nulls: &'a BitVec, low: i64, high: i64 },
}

impl<'a> FusedMatcher<'a> {
    #[inline(always)]
    fn matches(&self, i: usize) -> bool {
        match self {
            FusedMatcher::Like { col, matcher } => {
                col.get(i).map(|s| matcher.matches(s)).unwrap_or(false)
            }
            FusedMatcher::NotLike { col, matcher } => {
                col.get(i).map(|s| !matcher.matches(s)).unwrap_or(false)
            }
            FusedMatcher::CompareInt64 { data, nulls, op, target } => {
                if i >= data.len() || nulls.get(i) { return false; }
                let val = data[i];
                match op {
                    CompareOp::Equal => val == *target,
                    CompareOp::NotEqual => val != *target,
                    CompareOp::LessThan => val < *target,
                    CompareOp::LessEqual => val <= *target,
                    CompareOp::GreaterThan => val > *target,
                    CompareOp::GreaterEqual => val >= *target,
                    _ => false,
                }
            }
            FusedMatcher::CompareFloat64 { data, nulls, op, target } => {
                if i >= data.len() || nulls.get(i) { return false; }
                let val = data[i];
                match op {
                    CompareOp::Equal => (val - target).abs() < f64::EPSILON,
                    CompareOp::NotEqual => (val - target).abs() >= f64::EPSILON,
                    CompareOp::LessThan => val < *target,
                    CompareOp::LessEqual => val <= *target,
                    CompareOp::GreaterThan => val > *target,
                    CompareOp::GreaterEqual => val >= *target,
                    _ => false,
                }
            }
            FusedMatcher::RangeInt64 { data, nulls, low, high } => {
                if i >= data.len() || nulls.get(i) { return false; }
                let val = data[i];
                val >= *low && val <= *high
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn make_row(id: u64, name: &str, age: i64) -> Row {
        let mut row = Row::new(id);
        row.set("name", name);
        row.set("age", Value::Int64(age));
        row
    }

    #[test]
    fn test_compare_filter() {
        let row = make_row(1, "John", 30);

        let filter = Filter::Compare {
            field: "age".to_string(),
            op: CompareOp::GreaterThan,
            value: Value::Int64(25),
        };
        assert!(filter.matches(&row));

        let filter = Filter::Compare {
            field: "age".to_string(),
            op: CompareOp::LessThan,
            value: Value::Int64(25),
        };
        assert!(!filter.matches(&row));
    }

    #[test]
    fn test_like_filter() {
        let row = make_row(1, "John Smith", 30);

        let filter = Filter::Like {
            field: "name".to_string(),
            pattern: "John%".to_string(),
        };
        assert!(filter.matches(&row));

        let filter = Filter::Like {
            field: "name".to_string(),
            pattern: "%Smith".to_string(),
        };
        assert!(filter.matches(&row));
    }

    #[test]
    fn test_and_filter() {
        let row = make_row(1, "John", 30);

        let filter = Filter::And(vec![
            Filter::Compare {
                field: "age".to_string(),
                op: CompareOp::GreaterThan,
                value: Value::Int64(25),
            },
            Filter::Compare {
                field: "name".to_string(),
                op: CompareOp::Equal,
                value: Value::String("John".to_string()),
            },
        ]);
        assert!(filter.matches(&row));
    }

    #[test]
    fn test_or_filter() {
        let row = make_row(1, "John", 30);

        let filter = Filter::Or(vec![
            Filter::Compare {
                field: "age".to_string(),
                op: CompareOp::LessThan,
                value: Value::Int64(25),
            },
            Filter::Compare {
                field: "name".to_string(),
                op: CompareOp::Equal,
                value: Value::String("John".to_string()),
            },
        ]);
        assert!(filter.matches(&row));
    }
}

