# Requirements Traceability - Deep Dive: Multi-Language Implementation

## Language-Specific Considerations

### Python Implementation

**Strengths**:
- Rich ecosystem (Typer, Rich, Pydantic, SQLAlchemy)
- Excellent for rapid prototyping
- Strong AI/ML integration
- Great for data processing

**Architecture**:
```python
# Core models with Pydantic
from pydantic import BaseModel, Field
from typing import Optional, List
from datetime import datetime
from enum import Enum

class RequirementType(str, Enum):
    EPIC = "epic"
    FEATURE = "feature"
    STORY = "story"
    TASK = "task"

class Requirement(BaseModel):
    id: str = Field(default_factory=lambda: str(uuid4()))
    type: RequirementType
    title: str
    description: Optional[str] = None
    status: str = "draft"
    priority: str = "medium"
    created_at: datetime = Field(default_factory=datetime.now)
    
    class Config:
        json_schema_extra = {
            "example": {
                "id": "REQ-001",
                "type": "story",
                "title": "User can login",
                "status": "active"
            }
        }

# CLI with Typer
import typer
from rich.console import Console
from rich.table import Table

app = typer.Typer()
console = Console()

@app.command()
def create(
    req_type: RequirementType,
    title: str,
    description: Optional[str] = None
):
    """Create a new requirement"""
    req = Requirement(type=req_type, title=title, description=description)
    storage.create_requirement(req)
    console.print(f"[green]✓[/green] Created {req_type}: {title}")

@app.command()
def list_reqs(
    req_type: Optional[RequirementType] = None,
    status: Optional[str] = None
):
    """List requirements"""
    reqs = storage.list_requirements(type=req_type, status=status)
    
    table = Table(title="Requirements")
    table.add_column("ID", style="cyan")
    table.add_column("Type", style="magenta")
    table.add_column("Title", style="green")
    table.add_column("Status", style="yellow")
    
    for req in reqs:
        table.add_row(req.id, req.type, req.title, req.status)
    
    console.print(table)
```

### Go Implementation

**Strengths**:
- Excellent performance
- Strong concurrency support
- Single binary deployment
- Great for CLI tools (Cobra, Bubble Tea)

**Architecture**:
```go
package main

import (
    "github.com/spf13/cobra"
    "github.com/charmbracelet/bubbletea"
)

// Core types
type RequirementType string

const (
    Epic    RequirementType = "epic"
    Feature RequirementType = "feature"
    Story   RequirementType = "story"
    Task    RequirementType = "task"
)

type Requirement struct {
    ID          string          `json:"id"`
    Type        RequirementType `json:"type"`
    Title       string          `json:"title"`
    Description string          `json:"description,omitempty"`
    Status      string          `json:"status"`
    Priority    string          `json:"priority"`
    CreatedAt   time.Time       `json:"created_at"`
    UpdatedAt   time.Time       `json:"updated_at"`
}

// Storage interface
type Storage interface {
    CreateRequirement(req *Requirement) error
    GetRequirement(id string) (*Requirement, error)
    ListRequirements(filters map[string]string) ([]*Requirement, error)
    UpdateRequirement(req *Requirement) error
    DeleteRequirement(id string) error
}

// SQLite implementation
type SQLiteStorage struct {
    db *sql.DB
}

func (s *SQLiteStorage) CreateRequirement(req *Requirement) error {
    query := `
        INSERT INTO requirements (id, type, title, description, status, priority, created_at, updated_at)
        VALUES (?, ?, ?, ?, ?, ?, ?, ?)
    `
    _, err := s.db.Exec(query, req.ID, req.Type, req.Title, req.Description, 
                        req.Status, req.Priority, req.CreatedAt, req.UpdatedAt)
    return err
}

// CLI with Cobra
var rootCmd = &cobra.Command{
    Use:   "rtm",
    Short: "Requirements Traceability Management",
}

var createCmd = &cobra.Command{
    Use:   "create [type] [title]",
    Short: "Create a new requirement",
    Args:  cobra.ExactArgs(2),
    Run: func(cmd *cobra.Command, args []string) {
        reqType := RequirementType(args[0])
        title := args[1]
        
        req := &Requirement{
            ID:        generateID(),
            Type:      reqType,
            Title:     title,
            Status:    "draft",
            Priority:  "medium",
            CreatedAt: time.Now(),
            UpdatedAt: time.Now(),
        }
        
        if err := storage.CreateRequirement(req); err != nil {
            fmt.Fprintf(os.Stderr, "Error: %v\n", err)
            os.Exit(1)
        }
        
        fmt.Printf("✓ Created %s: %s\n", reqType, title)
    },
}

// TUI with Bubble Tea
type model struct {
    requirements []*Requirement
    cursor       int
    selected     map[int]struct{}
}

func (m model) Init() tea.Cmd {
    return nil
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg := msg.(type) {
    case tea.KeyMsg:
        switch msg.String() {
        case "q", "ctrl+c":
            return m, tea.Quit
        case "up", "k":
            if m.cursor > 0 {
                m.cursor--
            }
        case "down", "j":
            if m.cursor < len(m.requirements)-1 {
                m.cursor++
            }
        case " ":
            _, ok := m.selected[m.cursor]
            if ok {
                delete(m.selected, m.cursor)
            } else {
                m.selected[m.cursor] = struct{}{}
            }
        }
    }
    return m, nil
}

func (m model) View() string {
    s := "Requirements:\n\n"
    
    for i, req := range m.requirements {
        cursor := " "
        if m.cursor == i {
            cursor = ">"
        }
        
        checked := " "
        if _, ok := m.selected[i]; ok {
            checked = "x"
        }
        
        s += fmt.Sprintf("%s [%s] %s: %s\n", cursor, checked, req.Type, req.Title)
    }
    
    s += "\nPress q to quit.\n"
    return s
}
```

### Rust Implementation

**Strengths**:
- Memory safety without garbage collection
- Excellent performance
- Strong type system
- Great for systems programming

**Architecture**:
```rust
use serde::{Deserialize, Serialize};
use chrono::{DateTime, Utc};
use clap::{Parser, Subcommand};
use ratatui::{
    backend::CrosstermBackend,
    widgets::{Block, Borders, List, ListItem},
    Terminal,
};

// Core types
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum RequirementType {
    Epic,
    Feature,
    Story,
    Task,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Requirement {
    pub id: String,
    #[serde(rename = "type")]
    pub req_type: RequirementType,
    pub title: String,
    pub description: Option<String>,
    pub status: String,
    pub priority: String,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
}

// Storage trait
pub trait Storage {
    fn create_requirement(&mut self, req: &Requirement) -> Result<(), Box<dyn std::error::Error>>;
    fn get_requirement(&self, id: &str) -> Result<Option<Requirement>, Box<dyn std::error::Error>>;
    fn list_requirements(&self, filters: &HashMap<String, String>) -> Result<Vec<Requirement>, Box<dyn std::error::Error>>;
}

// SQLite implementation
pub struct SQLiteStorage {
    conn: rusqlite::Connection,
}

impl Storage for SQLiteStorage {
    fn create_requirement(&mut self, req: &Requirement) -> Result<(), Box<dyn std::error::Error>> {
        self.conn.execute(
            "INSERT INTO requirements (id, type, title, description, status, priority, created_at, updated_at)
             VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8)",
            params![
                &req.id,
                serde_json::to_string(&req.req_type)?,
                &req.title,
                &req.description,
                &req.status,
                &req.priority,
                req.created_at.to_rfc3339(),
                req.updated_at.to_rfc3339(),
            ],
        )?;
        Ok(())
    }
    
    fn get_requirement(&self, id: &str) -> Result<Option<Requirement>, Box<dyn std::error::Error>> {
        let mut stmt = self.conn.prepare(
            "SELECT id, type, title, description, status, priority, created_at, updated_at
             FROM requirements WHERE id = ?1"
        )?;
        
        let req = stmt.query_row(params![id], |row| {
            Ok(Requirement {
                id: row.get(0)?,
                req_type: serde_json::from_str(&row.get::<_, String>(1)?)?,
                title: row.get(2)?,
                description: row.get(3)?,
                status: row.get(4)?,
                priority: row.get(5)?,
                created_at: DateTime::parse_from_rfc3339(&row.get::<_, String>(6)?)?.with_timezone(&Utc),
                updated_at: DateTime::parse_from_rfc3339(&row.get::<_, String>(7)?)?.with_timezone(&Utc),
            })
        }).optional()?;
        
        Ok(req)
    }
}

// CLI with Clap
#[derive(Parser)]
#[command(name = "rtm")]
#[command(about = "Requirements Traceability Management", long_about = None)]
struct Cli {
    #[command(subcommand)]
    command: Commands,
}

#[derive(Subcommand)]
enum Commands {
    Create {
        #[arg(value_enum)]
        req_type: RequirementType,
        title: String,
        #[arg(short, long)]
        description: Option<String>,
    },
    List {
        #[arg(short, long)]
        req_type: Option<RequirementType>,
        #[arg(short, long)]
        status: Option<String>,
    },
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let cli = Cli::parse();
    let mut storage = SQLiteStorage::new("requirements.db")?;
    
    match &cli.command {
        Commands::Create { req_type, title, description } => {
            let req = Requirement {
                id: Uuid::new_v4().to_string(),
                req_type: req_type.clone(),
                title: title.clone(),
                description: description.clone(),
                status: "draft".to_string(),
                priority: "medium".to_string(),
                created_at: Utc::now(),
                updated_at: Utc::now(),
            };
            
            storage.create_requirement(&req)?;
            println!("✓ Created {:?}: {}", req_type, title);
        }
        Commands::List { req_type, status } => {
            let mut filters = HashMap::new();
            if let Some(t) = req_type {
                filters.insert("type".to_string(), format!("{:?}", t).to_lowercase());
            }
            if let Some(s) = status {
                filters.insert("status".to_string(), s.clone());
            }
            
            let reqs = storage.list_requirements(&filters)?;
            for req in reqs {
                println!("{} | {:?} | {}", req.id, req.req_type, req.title);
            }
        }
    }
    
    Ok(())
}
```

### TypeScript Implementation

**Strengths**:
- Type safety for JavaScript
- Excellent for web integration
- Rich ecosystem (npm)
- Great for Node.js CLI tools

**Architecture**:
```typescript
// Core types
export enum RequirementType {
    Epic = 'epic',
    Feature = 'feature',
    Story = 'story',
    Task = 'task',
}

export interface Requirement {
    id: string;
    type: RequirementType;
    title: string;
    description?: string;
    status: string;
    priority: string;
    createdAt: Date;
    updatedAt: Date;
}

// Storage interface
export interface Storage {
    createRequirement(req: Requirement): Promise<void>;
    getRequirement(id: string): Promise<Requirement | null>;
    listRequirements(filters?: Record<string, string>): Promise<Requirement[]>;
}

// SQLite implementation
import Database from 'better-sqlite3';

export class SQLiteStorage implements Storage {
    private db: Database.Database;
    
    constructor(dbPath: string) {
        this.db = new Database(dbPath);
        this.initSchema();
    }
    
    async createRequirement(req: Requirement): Promise<void> {
        const stmt = this.db.prepare(`
            INSERT INTO requirements (id, type, title, description, status, priority, created_at, updated_at)
            VALUES (?, ?, ?, ?, ?, ?, ?, ?)
        `);
        
        stmt.run(
            req.id,
            req.type,
            req.title,
            req.description,
            req.status,
            req.priority,
            req.createdAt.toISOString(),
            req.updatedAt.toISOString()
        );
    }
}

// CLI with Commander
import { Command } from 'commander';
import chalk from 'chalk';

const program = new Command();

program
    .name('rtm')
    .description('Requirements Traceability Management')
    .version('1.0.0');

program
    .command('create <type> <title>')
    .description('Create a new requirement')
    .option('-d, --description <description>', 'Requirement description')
    .action(async (type: string, title: string, options) => {
        const req: Requirement = {
            id: crypto.randomUUID(),
            type: type as RequirementType,
            title,
            description: options.description,
            status: 'draft',
            priority: 'medium',
            createdAt: new Date(),
            updatedAt: new Date(),
        };
        
        await storage.createRequirement(req);
        console.log(chalk.green(`✓ Created ${type}: ${title}`));
    });

program.parse();
```

## Cross-Language Interoperability

### Shared Data Format (Protocol Buffers)

```protobuf
syntax = "proto3";

package rtm;

enum RequirementType {
    EPIC = 0;
    FEATURE = 1;
    STORY = 2;
    TASK = 3;
}

message Requirement {
    string id = 1;
    RequirementType type = 2;
    string title = 3;
    string description = 4;
    string status = 5;
    string priority = 6;
    int64 created_at = 7;
    int64 updated_at = 8;
}

service RequirementService {
    rpc CreateRequirement(Requirement) returns (Requirement);
    rpc GetRequirement(GetRequirementRequest) returns (Requirement);
    rpc ListRequirements(ListRequirementsRequest) returns (ListRequirementsResponse);
}
```

### Shared SQLite Database

All language implementations can share the same SQLite database:

```sql
-- Common schema for all languages
CREATE TABLE requirements (
    id TEXT PRIMARY KEY,
    type TEXT NOT NULL,
    title TEXT NOT NULL,
    description TEXT,
    status TEXT DEFAULT 'draft',
    priority TEXT DEFAULT 'medium',
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
```

