//! # Compiler Orchestration
//!
//! This module provides the high-level API for triggering the compilation process.
//! It handles the transition between different compiler phases: Frontend -> IR -> Backend.

use crate::backend;
use crate::common::files::FileManager;
use crate::common::symbols::Symbol;
use crate::frontends::ts::TypescriptFrontend;
use crate::frontends::Frontend;
use crate::ir;
use anyhow::Result;
use std::path::Path;

/// The result of a successful compilation process.
/// It contains the final binary and the metadata needed for debugging.
pub struct CompilationUnit {
    /// The raw binary data formatted as Prometeu ByteCode (PBC).
    /// This is what gets written to a `.pbc` file.
    pub rom: Vec<u8>,
    
    /// The list of debug symbols discovered during compilation.
    /// These are used to map bytecode offsets back to source code locations.
    pub symbols: Vec<Symbol>,
}

impl CompilationUnit {
    /// Writes the compilation results (PBC binary, disassembly, and symbols) to the disk.
    /// 
    /// # Arguments
    /// * `out` - The base path for the output `.pbc` file.
    /// * `emit_disasm` - If true, a `.disasm` file will be created next to the output.
    /// * `emit_symbols` - If true, a `.json` symbols file will be created next to the output.
    pub fn export(&self, out: &Path, emit_disasm: bool, emit_symbols: bool) -> Result<()> {
        let artifacts = backend::artifacts::Artifacts::new(self.rom.clone(), self.symbols.clone());
        artifacts.export(out, emit_disasm, emit_symbols)
    }
}

/// Orchestrates the compilation of a Prometeu project starting from an entry file.
///
/// This function executes the full compiler pipeline:
/// 1. **Frontend**: Loads and parses the entry file (and its dependencies).
///    Currently, it uses the `TypescriptFrontend`.
/// 2. **IR Generation**: The frontend produces a high-level Intermediate Representation (IR).
/// 3. **Validation**: Checks the IR for consistency and VM compatibility.
/// 4. **Backend**: Lowers the IR into final Prometeu ByteCode.
///
/// # Errors
/// Returns an error if parsing fails, validation finds issues, or code generation fails.
///
/// # Example
/// ```no_run
/// use std::path::Path;
/// let entry = Path::new("src/main.ts");
/// let unit = prometeu_compiler::compiler::compile(entry).expect("Failed to compile");
/// unit.export(Path::new("build/program.pbc"), true, true).unwrap();
/// ```
pub fn compile(entry: &Path) -> Result<CompilationUnit> {
    let mut file_manager = FileManager::new();
    
    // 1. Select Frontend (Currently only TS is supported)
    // The frontend is responsible for parsing source code and producing the IR.
    let frontend = TypescriptFrontend;
    
    // 2. Compile to IR (Intermediate Representation)
    // This step abstracts away source-specific syntax (like TypeScript) into a
    // generic set of instructions that the backend can understand.
    let ir_module = frontend.compile_to_ir(entry, &mut file_manager)
        .map_err(|bundle| anyhow::anyhow!("Compilation failed with {} errors", bundle.diagnostics.len()))?;
        
    // 3. IR Validation
    // Ensures the generated IR is sound and doesn't violate any VM constraints
    // before we spend time generating bytecode.
    ir::validate::validate_module(&ir_module)
        .map_err(|bundle| anyhow::anyhow!("IR Validation failed: {:?}", bundle))?;
        
    // 4. Emit Bytecode
    // The backend takes the validated IR and produces the final binary executable.
    let result = backend::emit_module(&ir_module, &file_manager)?;
    
    Ok(CompilationUnit {
        rom: result.rom,
        symbols: result.symbols,
    })
}