(** SPDX-License-Identifier: MPL-2.0 *)
(* SPDX-FileCopyrightText: 2026 Jonathan D.A. Jewell *)

(** Native Backend Implementation (Stub)
    
    Placeholder for native code generation backend.
    Will generate x86-64, ARM64, and RISC-V assembly.
*)

open Ast
open Architecture

(** Native Backend Context *)
type context = {
  config : native_config;
  capabilities : capability list;
}

(** Native Backend Implementation *)
module Native_backend : PROCESSOR_BACKEND = struct
  type context = context
  
  let create_context () : context = {
    config = {
      target_arch = `X86_64;
      target_os = `Linux;
      optimization_level = 2;
      enable_lto = true;
      enable_debug = false;
    };
    capabilities = [
      BasicArithmetic;
      MemoryManagement;
      ControlFlow;
      FunctionCalls;
      SIMDOperations;  (* Native backends support SIMD *)
    ];
  }
  
  let get_capabilities (ctx : context) : capability list = ctx.capabilities
  
  let supports_feature (ctx : context) (feature : string) : bool =
    match feature with
    | "simd" -> true
    | "multithreading" -> true
    | "hardware_acceleration" -> true
    | _ -> false
  
  let emit_prologue (ctx : context) : string =
    match ctx.config.target_arch with
    | `X86_64 -> 
        ".text\n"
        ^ ".globl main\n"
        ^ "main:\n"
        ^ "  push %rbp\n"
        ^ "  mov %rsp, %rbp\n"
    | `ARM64 -> 
        ".text\n"
        ^ ".globl main\n"
        ^ "main:\n"
        ^ "  stp x29, x30, [sp, #-16]!\n"
        ^ "  mov x29, sp\n"
    | _ -> ""
  
  let emit_epilogue (ctx : context) : string =
    match ctx.config.target_arch with
    | `X86_64 -> 
        "  mov $0, %rax\n"
        ^ "  pop %rbp\n"
        ^ "  ret\n"
    | `ARM64 -> 
        "  mov w0, #0\n"
        ^ "  ldp x29, x30, [sp], #16\n"
        ^ "  ret\n"
    | _ -> ""
  
  let emit_function (ctx : context) (fd : fn_decl) : string =
    let prologue = emit_prologue ctx in
    let body = emit_expression ctx fd.fd_body in
    let epilogue = emit_epilogue ctx in
    Printf.sprintf "%s%s%s" prologue body epilogue
  
  let emit_expression (ctx : context) (expr : expr) : string =
    match expr with
    | ExprLit (LitInt (n, _)) -> 
        begin match ctx.config.target_arch with
        | `X86_64 -> Printf.sprintf "  mov $%d, %%rax\n" n
        | `ARM64 -> Printf.sprintf "  mov w0, #%d\n" n
        | _ -> ""
        end
    | _ -> "  # TODO: Native expression emission\n"
  
  let emit_statement (ctx : context) (stmt : stmt) : string =
    match stmt with
    | StmtLet sl -> emit_expression ctx sl.sl_value
    | StmtExpr e -> emit_expression ctx e
    | _ -> "  # TODO: Native statement emission\n"
  
  let generate_code (ctx : context) (program : program) : string =
    let prologue = emit_prologue ctx in
    let function_code = String.concat "\n" (List.map (emit_function ctx) program.top_levels) in
    let epilogue = emit_epilogue ctx in
    prologue ^ "\n" ^ function_code ^ "\n" ^ epilogue
  
  (* Optimization passes *)
  let run_optimizations (ctx : context) (program : program) : program = program
  let inline_functions (ctx : context) (program : program) : program = program
  let constant_folding (ctx : context) (program : program) : program = program
  let dead_code_elimination (ctx : context) (program : program) : program = program
end