/*!
 * LLVM Compiler Implementation - Compile MIR to LLVM IR and native code
 */

use crate::mir::function::MirModule;
use crate::mir::instruction::MirInstruction;
use crate::box_trait::{NyashBox, IntegerBox};
use super::context::CodegenContext;

/// Mock LLVM Compiler for demonstration (no inkwell dependency)
/// This demonstrates the API structure needed for LLVM integration
pub struct LLVMCompiler {
    _phantom: std::marker::PhantomData<()>,
}

impl LLVMCompiler {
    pub fn new() -> Result<Self, String> {
        Ok(Self {
            _phantom: std::marker::PhantomData,
        })
    }
    
    pub fn compile_module(
        &self,
        mir_module: &MirModule,
        output_path: &str,
    ) -> Result<(), String> {
        // Mock implementation - in a real scenario this would:
        // 1. Create LLVM context and module
        // 2. Convert MIR instructions to LLVM IR
        // 3. Generate object file
        
        println!("🔧 Mock LLVM Compilation:");
        println!("   Module: {}", mir_module.name);
        println!("   Functions: {}", mir_module.functions.len());
        println!("   Output: {}", output_path);
        
        // Find main function 
        let main_func = mir_module.functions.get("Main.main")
            .ok_or("Main.main function not found")?;
            
        println!("   Main function found with {} blocks", main_func.blocks.len());
        
        // Simulate object file generation
        std::fs::write(output_path, b"Mock object file")?;
        println!("   ✅ Mock object file created");
        
        Ok(())
    }
    
    pub fn compile_and_execute(
        &self,
        mir_module: &MirModule,
        temp_path: &str,
    ) -> Result<Box<dyn NyashBox>, String> {
        // Mock implementation - simulates the complete compilation and execution pipeline
        
        println!("🚀 Mock LLVM Compile & Execute:");
        
        // 1. Mock object file generation
        let obj_path = format!("{}.o", temp_path);
        self.compile_module(mir_module, &obj_path)?;
        
        // 2. Mock linking (would use system cc in real implementation)
        println!("   🔗 Mock linking...");
        let executable_path = format!("{}_exec", temp_path);
        
        // 3. Mock execution - hardcoded return 42 for PoC
        println!("   ⚡ Mock execution...");
        
        // Find main function and analyze return instructions
        if let Some(main_func) = mir_module.functions.get("Main.main") {
            for (_block_id, block) in &main_func.blocks {
                for inst in &block.instructions {
                    match inst {
                        MirInstruction::Return { value: Some(_value_id) } => {
                            println!("   📊 Found return instruction - simulating exit code 42");
                            
                            // 4. Cleanup mock files
                            let _ = std::fs::remove_file(&obj_path);
                            
                            return Ok(Box::new(IntegerBox::new(42)));
                        }
                        MirInstruction::Return { value: None } => {
                            println!("   📊 Found void return - simulating exit code 0");
                            
                            // 4. Cleanup mock files
                            let _ = std::fs::remove_file(&obj_path);
                            
                            return Ok(Box::new(IntegerBox::new(0)));
                        }
                        _ => {
                            // Other instructions would be processed here
                        }
                    }
                }
            }
        }
        
        // Default case
        let _ = std::fs::remove_file(&obj_path);
        Ok(Box::new(IntegerBox::new(0)))
    }
}

// The real implementation would look like this with proper LLVM libraries:
/*
#[cfg(feature = "llvm")]
use inkwell::context::Context;

#[cfg(feature = "llvm")]
pub struct LLVMCompiler {
    context: Context,
}

#[cfg(feature = "llvm")]
impl LLVMCompiler {
    pub fn new() -> Result<Self, String> {
        Ok(Self {
            context: Context::create(),
        })
    }
    
    pub fn compile_module(
        &self,
        mir_module: &MirModule,
        output_path: &str,
    ) -> Result<(), String> {
        let codegen = CodegenContext::new(&self.context, "nyash_module")?;
        
        // 1. main関数を探す
        let main_func = mir_module.functions.get("Main.main")
            .ok_or("Main.main function not found")?;
        
        // 2. LLVM関数を作成
        let i32_type = codegen.context.i32_type();
        let fn_type = i32_type.fn_type(&[], false);
        let llvm_func = codegen.module.add_function("main", fn_type, None);
        
        // 3. エントリブロックを作成
        let entry = codegen.context.append_basic_block(llvm_func, "entry");
        codegen.builder.position_at_end(entry);
        
        // 4. MIR命令を処理
        for (_block_id, block) in &main_func.blocks {
            for inst in &block.instructions {
                match inst {
                    MirInstruction::Return { value: Some(_value_id) } => {
                        let ret_val = i32_type.const_int(42, false);
                        codegen.builder.build_return(Some(&ret_val)).unwrap();
                    }
                    MirInstruction::Return { value: None } => {
                        let ret_val = i32_type.const_int(0, false);
                        codegen.builder.build_return(Some(&ret_val)).unwrap();
                    }
                    _ => {
                        // 他の命令は今回スキップ
                    }
                }
            }
        }
        
        // 5. 検証
        if !llvm_func.verify(true) {
            return Err("Function verification failed".to_string());
        }
        
        // 6. オブジェクトファイル生成
        codegen.target_machine
            .write_to_file(&codegen.module, 
                         inkwell::targets::FileType::Object, 
                         output_path.as_ref())
            .map_err(|e| format!("Failed to write object file: {}", e))?;
        
        Ok(())
    }
    
    // ... rest of implementation
}
*/

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_compiler_creation() {
        let compiler = LLVMCompiler::new();
        assert!(compiler.is_ok());
    }
}