//! The serialized instructions of the current transaction.
//!
//! The _instructions sysvar_ provides access to the serialized instruction data
//! for the currently-running transaction. This allows for [instruction
//! introspection][in], which is required for correctly interoperating with
//! native programs like the [secp256k1] and [ed25519] programs.
//!
//! [in]: https://docs.solanalabs.com/implemented-proposals/instruction_introspection
//! [secp256k1]: https://docs.rs/solana-secp256k1-program/latest/rialo_s_secp256k1_program/
//! [ed25519]: https://docs.rs/solana-ed25519-program/latest/rialo_s_ed25519_program/
//!
//! Unlike other sysvars, the data in the instructions sysvar is not accessed
//! through a type that implements the [`Sysvar`] trait. Instead, the
//! instruction sysvar is accessed through several free functions within this
//! module.
//!
//! [`Sysvar`]: https://docs.rs/solana-sysvar/latest/solana_sysvar/trait.Sysvar.html
//!
//! See also the Solana [documentation on the instructions sysvar][sdoc].
//!
//! [sdoc]: https://docs.solanalabs.com/runtime/sysvars#instructions
//!
//! # Examples
//!
//! For a complete example of how the instructions sysvar is used see the
//! documentation for [`secp256k1_instruction`] in the `solana-sdk` crate.
//!
//! [`secp256k1_instruction`]: https://docs.rs/solana-sdk/latest/rialo_s_sdk/secp256k1_instruction/index.html

#![cfg_attr(docsrs, feature(doc_auto_cfg))]
#![allow(clippy::arithmetic_side_effects)]

#[cfg(feature = "dev-context-only-utils")]
use qualifier_attr::qualifiers;
use rialo_s_account_info::AccountInfo;
use rialo_s_instruction::{AccountMeta, Instruction};
use rialo_s_program_error::ProgramError;
pub use rialo_s_sdk_ids::sysvar::instructions::{check_id, id, ID};
use rialo_s_serialize_utils::{read_pubkey, read_slice, read_u16, read_u8};
use rialo_sanitize::SanitizeError;
#[cfg(not(target_os = "solana"))]
use {
    bitflags::bitflags,
    rialo_s_instruction::BorrowedInstruction,
    rialo_s_serialize_utils::{append_slice, append_u16, append_u8},
};

/// Instructions sysvar, dummy type.
///
/// This type exists for consistency with other sysvar modules, but is a dummy
/// type that does not contain sysvar data. It implements the [`SysvarId`] trait
/// but does not implement the [`Sysvar`] trait.
///
/// [`SysvarId`]: https://docs.rs/solana-sysvar-id/latest/rialo_s_sysvar_id/trait.SysvarId.html
/// [`Sysvar`]: https://docs.rs/solana-sysvar/latest/solana_sysvar/trait.Sysvar.html
///
/// Use the free functions in this module to access the instructions sysvar.
pub struct Instructions();

rialo_s_sysvar_id::impl_sysvar_id!(Instructions);

/// Construct the account data for the instructions sysvar.
///
/// This function is used by the runtime and not available to Solana programs.
#[cfg(not(target_os = "solana"))]
pub fn construct_instructions_data(instructions: &[BorrowedInstruction<'_>]) -> Vec<u8> {
    let mut data = serialize_instructions(instructions);
    // add room for current instruction index.
    data.resize(data.len() + 2, 0);

    data
}

#[cfg(not(target_os = "solana"))]
bitflags! {
    struct InstructionsSysvarAccountMeta: u8 {
        const IS_SIGNER = 0b00000001;
        const IS_WRITABLE = 0b00000010;
    }
}

// First encode the number of instructions:
// [0..2 - num_instructions
//
// Then a table of offsets of where to find them in the data
//  3..2 * num_instructions table of instruction offsets
//
// Each instruction is then encoded as:
//   0..2 - num_accounts
//   2 - meta_byte -> (bit 0 signer, bit 1 is_writable)
//   3..35 - pubkey - 32 bytes
//   35..67 - program_id
//   67..69 - data len - u16
//   69..data_len - data
#[cfg(not(target_os = "solana"))]
#[cfg_attr(feature = "dev-context-only-utils", qualifiers(pub))]
fn serialize_instructions(instructions: &[BorrowedInstruction<'_>]) -> Vec<u8> {
    // 64 bytes is a reasonable guess, calculating exactly is slower in benchmarks
    let mut data = Vec::with_capacity(instructions.len() * (32 * 2));
    append_u16(&mut data, instructions.len() as u16);
    for _ in 0..instructions.len() {
        append_u16(&mut data, 0);
    }

    for (i, instruction) in instructions.iter().enumerate() {
        let start_instruction_offset = data.len() as u16;
        let start = 2 + (2 * i);
        data[start..start + 2].copy_from_slice(&start_instruction_offset.to_le_bytes());
        append_u16(&mut data, instruction.accounts.len() as u16);
        for account_meta in &instruction.accounts {
            let mut account_meta_flags = InstructionsSysvarAccountMeta::empty();
            if account_meta.is_signer {
                account_meta_flags |= InstructionsSysvarAccountMeta::IS_SIGNER;
            }
            if account_meta.is_writable {
                account_meta_flags |= InstructionsSysvarAccountMeta::IS_WRITABLE;
            }
            append_u8(&mut data, account_meta_flags.bits());
            append_slice(&mut data, account_meta.pubkey.as_ref());
        }

        append_slice(&mut data, instruction.program_id.as_ref());
        append_u16(&mut data, instruction.data.len() as u16);
        append_slice(&mut data, instruction.data);
    }
    data
}

/// Load the current `Instruction`'s index in the currently executing
/// `Transaction`.
///
/// `data` is the instructions sysvar account data.
///
/// Unsafe because the sysvar accounts address is not checked; only used
/// internally after such a check.
fn load_current_index(data: &[u8]) -> u16 {
    let mut instr_fixed_data = [0u8; 2];
    let len = data.len();
    instr_fixed_data.copy_from_slice(&data[len - 2..len]);
    u16::from_le_bytes(instr_fixed_data)
}

/// Load the current `Instruction`'s index in the currently executing
/// `Transaction`.
///
/// # Errors
///
/// Returns [`ProgramError::UnsupportedSysvar`] if the given account's ID is not equal to [`ID`].
pub fn load_current_index_checked(
    instruction_sysvar_account_info: &AccountInfo<'_>,
) -> Result<u16, ProgramError> {
    if !check_id(instruction_sysvar_account_info.key) {
        return Err(ProgramError::UnsupportedSysvar);
    }

    let instruction_sysvar = instruction_sysvar_account_info.try_borrow_data()?;
    let index = load_current_index(&instruction_sysvar);
    Ok(index)
}

/// Store the current `Instruction`'s index in the instructions sysvar data.
pub fn store_current_index(data: &mut [u8], instruction_index: u16) {
    let last_index = data.len() - 2;
    data[last_index..last_index + 2].copy_from_slice(&instruction_index.to_le_bytes());
}

#[cfg_attr(feature = "dev-context-only-utils", qualifiers(pub))]
fn deserialize_instruction(index: usize, data: &[u8]) -> Result<Instruction, SanitizeError> {
    const IS_SIGNER_BIT: usize = 0;
    const IS_WRITABLE_BIT: usize = 1;

    let mut current = 0;
    let num_instructions = read_u16(&mut current, data)?;
    if index >= num_instructions as usize {
        return Err(SanitizeError::IndexOutOfBounds);
    }

    // index into the instruction byte-offset table.
    current += index * 2;
    let start = read_u16(&mut current, data)?;

    current = start as usize;
    let num_accounts = read_u16(&mut current, data)?;
    let mut accounts = Vec::with_capacity(num_accounts as usize);
    for _ in 0..num_accounts {
        let meta_byte = read_u8(&mut current, data)?;
        let mut is_signer = false;
        let mut is_writable = false;
        if meta_byte & (1 << IS_SIGNER_BIT) != 0 {
            is_signer = true;
        }
        if meta_byte & (1 << IS_WRITABLE_BIT) != 0 {
            is_writable = true;
        }
        let pubkey = read_pubkey(&mut current, data)?;
        accounts.push(AccountMeta {
            pubkey,
            is_signer,
            is_writable,
        });
    }
    let program_id = read_pubkey(&mut current, data)?;
    let data_len = read_u16(&mut current, data)?;
    let data = read_slice(&mut current, data, data_len as usize)?;
    Ok(Instruction {
        program_id,
        accounts,
        data,
    })
}

/// Load an `Instruction` in the currently executing `Transaction` at the
/// specified index.
///
/// `data` is the instructions sysvar account data.
///
/// Unsafe because the sysvar accounts address is not checked; only used
/// internally after such a check.
#[cfg_attr(feature = "dev-context-only-utils", qualifiers(pub))]
fn load_instruction_at(index: usize, data: &[u8]) -> Result<Instruction, SanitizeError> {
    deserialize_instruction(index, data)
}

/// Load an `Instruction` in the currently executing `Transaction` at the
/// specified index.
///
/// # Errors
///
/// Returns [`ProgramError::UnsupportedSysvar`] if the given account's ID is not equal to [`ID`].
pub fn load_instruction_at_checked(
    index: usize,
    instruction_sysvar_account_info: &AccountInfo<'_>,
) -> Result<Instruction, ProgramError> {
    if !check_id(instruction_sysvar_account_info.key) {
        return Err(ProgramError::UnsupportedSysvar);
    }

    let instruction_sysvar = instruction_sysvar_account_info.try_borrow_data()?;
    load_instruction_at(index, &instruction_sysvar).map_err(|err| match err {
        SanitizeError::IndexOutOfBounds => ProgramError::InvalidArgument,
        _ => ProgramError::InvalidInstructionData,
    })
}

/// Returns the `Instruction` relative to the current `Instruction` in the
/// currently executing `Transaction`.
///
/// # Errors
///
/// Returns [`ProgramError::UnsupportedSysvar`] if the given account's ID is not equal to [`ID`].
pub fn get_instruction_relative(
    index_relative_to_current: i64,
    instruction_sysvar_account_info: &AccountInfo<'_>,
) -> Result<Instruction, ProgramError> {
    if !check_id(instruction_sysvar_account_info.key) {
        return Err(ProgramError::UnsupportedSysvar);
    }

    let instruction_sysvar = instruction_sysvar_account_info.data.borrow();
    let current_index = load_current_index(&instruction_sysvar) as i64;
    let index = current_index.saturating_add(index_relative_to_current);
    if index < 0 {
        return Err(ProgramError::InvalidArgument);
    }
    load_instruction_at(
        current_index.saturating_add(index_relative_to_current) as usize,
        &instruction_sysvar,
    )
    .map_err(|err| match err {
        SanitizeError::IndexOutOfBounds => ProgramError::InvalidArgument,
        _ => ProgramError::InvalidInstructionData,
    })
}

#[cfg(test)]
mod tests {
    use rialo_s_account_info::AccountInfo;
    use rialo_s_instruction::{AccountMeta, BorrowedAccountMeta, BorrowedInstruction, Instruction};
    use rialo_s_program_error::ProgramError;
    use rialo_s_pubkey::Pubkey;
    use rialo_s_sdk_ids::sysvar::instructions::id;
    use rialo_sanitize::SanitizeError;

    use super::*;

    #[test]
    fn test_load_store_instruction() {
        let mut data = [4u8; 10];
        store_current_index(&mut data, 3);
        #[allow(deprecated)]
        let index = load_current_index(&data);
        assert_eq!(index, 3);
        assert_eq!([4u8; 8], data[0..8]);
    }

    #[derive(Copy, Clone)]
    struct MakeInstructionParams {
        program_id: Pubkey,
        account_key: Pubkey,
        is_signer: bool,
        is_writable: bool,
    }

    fn make_borrowed_instruction(params: &MakeInstructionParams) -> BorrowedInstruction<'_> {
        let MakeInstructionParams {
            program_id,
            account_key,
            is_signer,
            is_writable,
        } = params;
        BorrowedInstruction {
            program_id,
            accounts: vec![BorrowedAccountMeta {
                pubkey: account_key,
                is_signer: *is_signer,
                is_writable: *is_writable,
            }],
            data: &[0],
        }
    }

    fn make_instruction(params: MakeInstructionParams) -> Instruction {
        let MakeInstructionParams {
            program_id,
            account_key,
            is_signer,
            is_writable,
        } = params;
        Instruction {
            program_id,
            accounts: vec![AccountMeta {
                pubkey: account_key,
                is_signer,
                is_writable,
            }],
            data: vec![0],
        }
    }

    #[test]
    fn test_load_instruction_at_checked() {
        let program_id0 = Pubkey::new_unique();
        let program_id1 = Pubkey::new_unique();
        let account_key0 = Pubkey::new_unique();
        let account_key1 = Pubkey::new_unique();
        let params0 = MakeInstructionParams {
            program_id: program_id0,
            account_key: account_key0,
            is_signer: false,
            is_writable: false,
        };
        let params1 = MakeInstructionParams {
            program_id: program_id1,
            account_key: account_key1,
            is_signer: false,
            is_writable: false,
        };
        let instruction0 = make_instruction(params0);
        let instruction1 = make_instruction(params1);
        let borrowed_instruction0 = make_borrowed_instruction(&params0);
        let borrowed_instruction1 = make_borrowed_instruction(&params1);
        let key = id();
        let mut kelvins = 0;
        let mut data = construct_instructions_data(&[borrowed_instruction0, borrowed_instruction1]);
        let owner = rialo_s_sdk_ids::sysvar::id();
        let mut account_info = AccountInfo::new(
            &key,
            false,
            false,
            &mut kelvins,
            &mut data,
            &owner,
            false,
            0,
        );

        assert_eq!(
            instruction0,
            load_instruction_at_checked(0, &account_info).unwrap()
        );
        assert_eq!(
            instruction1,
            load_instruction_at_checked(1, &account_info).unwrap()
        );
        assert_eq!(
            Err(ProgramError::InvalidArgument),
            load_instruction_at_checked(2, &account_info)
        );

        let key = Pubkey::new_unique();
        account_info.key = &key;
        assert_eq!(
            Err(ProgramError::UnsupportedSysvar),
            load_instruction_at_checked(2, &account_info)
        );
    }

    #[test]
    fn test_load_current_index_checked() {
        let program_id0 = Pubkey::new_unique();
        let program_id1 = Pubkey::new_unique();
        let account_key0 = Pubkey::new_unique();
        let account_key1 = Pubkey::new_unique();
        let params0 = MakeInstructionParams {
            program_id: program_id0,
            account_key: account_key0,
            is_signer: false,
            is_writable: false,
        };
        let params1 = MakeInstructionParams {
            program_id: program_id1,
            account_key: account_key1,
            is_signer: false,
            is_writable: false,
        };
        let borrowed_instruction0 = make_borrowed_instruction(&params0);
        let borrowed_instruction1 = make_borrowed_instruction(&params1);

        let key = id();
        let mut kelvins = 0;
        let mut data = construct_instructions_data(&[borrowed_instruction0, borrowed_instruction1]);
        store_current_index(&mut data, 1);
        let owner = rialo_s_sdk_ids::sysvar::id();
        let mut account_info = AccountInfo::new(
            &key,
            false,
            false,
            &mut kelvins,
            &mut data,
            &owner,
            false,
            0,
        );

        assert_eq!(1, load_current_index_checked(&account_info).unwrap());
        {
            let mut data = account_info.try_borrow_mut_data().unwrap();
            store_current_index(&mut data, 0);
        }
        assert_eq!(0, load_current_index_checked(&account_info).unwrap());

        let key = Pubkey::new_unique();
        account_info.key = &key;
        assert_eq!(
            Err(ProgramError::UnsupportedSysvar),
            load_current_index_checked(&account_info)
        );
    }

    #[test]
    fn test_get_instruction_relative() {
        let program_id0 = Pubkey::new_unique();
        let program_id1 = Pubkey::new_unique();
        let program_id2 = Pubkey::new_unique();
        let account_key0 = Pubkey::new_unique();
        let account_key1 = Pubkey::new_unique();
        let account_key2 = Pubkey::new_unique();
        let params0 = MakeInstructionParams {
            program_id: program_id0,
            account_key: account_key0,
            is_signer: false,
            is_writable: false,
        };
        let params1 = MakeInstructionParams {
            program_id: program_id1,
            account_key: account_key1,
            is_signer: false,
            is_writable: false,
        };
        let params2 = MakeInstructionParams {
            program_id: program_id2,
            account_key: account_key2,
            is_signer: false,
            is_writable: false,
        };
        let instruction0 = make_instruction(params0);
        let instruction1 = make_instruction(params1);
        let instruction2 = make_instruction(params2);
        let borrowed_instruction0 = make_borrowed_instruction(&params0);
        let borrowed_instruction1 = make_borrowed_instruction(&params1);
        let borrowed_instruction2 = make_borrowed_instruction(&params2);

        let key = id();
        let mut kelvins = 0;
        let mut data = construct_instructions_data(&[
            borrowed_instruction0,
            borrowed_instruction1,
            borrowed_instruction2,
        ]);
        store_current_index(&mut data, 1);
        let owner = rialo_s_sdk_ids::sysvar::id();
        let mut account_info = AccountInfo::new(
            &key,
            false,
            false,
            &mut kelvins,
            &mut data,
            &owner,
            false,
            0,
        );

        assert_eq!(
            Err(ProgramError::InvalidArgument),
            get_instruction_relative(-2, &account_info)
        );
        assert_eq!(
            instruction0,
            get_instruction_relative(-1, &account_info).unwrap()
        );
        assert_eq!(
            instruction1,
            get_instruction_relative(0, &account_info).unwrap()
        );
        assert_eq!(
            instruction2,
            get_instruction_relative(1, &account_info).unwrap()
        );
        assert_eq!(
            Err(ProgramError::InvalidArgument),
            get_instruction_relative(2, &account_info)
        );
        {
            let mut data = account_info.try_borrow_mut_data().unwrap();
            store_current_index(&mut data, 0);
        }
        assert_eq!(
            Err(ProgramError::InvalidArgument),
            get_instruction_relative(-1, &account_info)
        );
        assert_eq!(
            instruction0,
            get_instruction_relative(0, &account_info).unwrap()
        );
        assert_eq!(
            instruction1,
            get_instruction_relative(1, &account_info).unwrap()
        );
        assert_eq!(
            instruction2,
            get_instruction_relative(2, &account_info).unwrap()
        );
        assert_eq!(
            Err(ProgramError::InvalidArgument),
            get_instruction_relative(3, &account_info)
        );

        let key = Pubkey::new_unique();
        account_info.key = &key;
        assert_eq!(
            Err(ProgramError::UnsupportedSysvar),
            get_instruction_relative(0, &account_info)
        );
    }

    #[test]
    fn test_serialize_instructions() {
        let program_id0 = Pubkey::new_unique();
        let program_id1 = Pubkey::new_unique();
        let id0 = Pubkey::new_unique();
        let id1 = Pubkey::new_unique();
        let id2 = Pubkey::new_unique();
        let id3 = Pubkey::new_unique();
        let params = vec![
            MakeInstructionParams {
                program_id: program_id0,
                account_key: id0,
                is_signer: false,
                is_writable: true,
            },
            MakeInstructionParams {
                program_id: program_id0,
                account_key: id1,
                is_signer: true,
                is_writable: true,
            },
            MakeInstructionParams {
                program_id: program_id1,
                account_key: id2,
                is_signer: false,
                is_writable: false,
            },
            MakeInstructionParams {
                program_id: program_id1,
                account_key: id3,
                is_signer: true,
                is_writable: false,
            },
        ];
        let instructions: Vec<Instruction> =
            params.clone().into_iter().map(make_instruction).collect();
        let borrowed_instructions: Vec<BorrowedInstruction<'_>> =
            params.iter().map(make_borrowed_instruction).collect();

        let serialized = serialize_instructions(&borrowed_instructions);

        // assert that deserialize_instruction is compatible with SanitizedMessage::serialize_instructions
        for (i, instruction) in instructions.iter().enumerate() {
            assert_eq!(
                deserialize_instruction(i, &serialized).unwrap(),
                *instruction
            );
        }
    }

    #[test]
    fn test_decompile_instructions_out_of_bounds() {
        let program_id0 = Pubkey::new_unique();
        let id0 = Pubkey::new_unique();
        let id1 = Pubkey::new_unique();
        let params = vec![
            MakeInstructionParams {
                program_id: program_id0,
                account_key: id0,
                is_signer: false,
                is_writable: true,
            },
            MakeInstructionParams {
                program_id: program_id0,
                account_key: id1,
                is_signer: true,
                is_writable: true,
            },
        ];
        let instructions: Vec<Instruction> =
            params.clone().into_iter().map(make_instruction).collect();
        let borrowed_instructions: Vec<BorrowedInstruction<'_>> =
            params.iter().map(make_borrowed_instruction).collect();

        let serialized = serialize_instructions(&borrowed_instructions);
        assert_eq!(
            deserialize_instruction(instructions.len(), &serialized).unwrap_err(),
            SanitizeError::IndexOutOfBounds,
        );
    }
}
