// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

//go:build linux && amd64

package main

import (
	"fmt"
	"os"
	"sort"

	"sourcedock.dev/petrbalvin/gasm-devkit/debug"
	"sourcedock.dev/petrbalvin/gasm-devkit/verify"
)

func cmdDebug(args []string) int {
	fs := newCommand("debug", "gasm debug <file.s> --func <name>", `
Interactive debugger for JIT-assembled amd64 functions.  Launches the
function in a traced subprocess (ptrace), then provides a REPL for
single-stepping, breakpoints, register and memory inspection.

REPL commands:
  break <label|addr>   set a breakpoint at a label or absolute address
  step [n]             single-step n instructions (default 1)
  continue             run until next breakpoint or exit
  regs                 print general-purpose registers
  x [addr] [len]       hex-dump memory (default: current PC, 64 bytes)
  labels               list function labels and offsets
  quit                 kill the debuggee and exit
`)
	target := fs.Bool("target", false, "") // hidden: debuggee subprocess mode
	funcName := fs.String("func", "", "function to debug")
	argsFile := fs.String("args", "", "file containing the ABI0 argument block")
	fs.Parse(args)

	// --- Debuggee mode (internal, spawned by the debugger) ---
	if *target {
		tmpDir := os.Getenv("GASM_DEBUG_TMP")
		if tmpDir == "" || fs.NArg() < 1 || *funcName == "" || *argsFile == "" {
			fmt.Fprintln(os.Stderr, "gasm debug --target: internal mode")
			return 2
		}
		if err := debug.RunTarget(fs.Arg(0), *funcName, *argsFile, tmpDir); err != nil {
			fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
			return 1
		}
		return 0
	}

	// --- Debugger mode (interactive REPL) ---
	if fs.NArg() < 1 || *funcName == "" {
		fmt.Fprintln(os.Stderr, "usage: gasm debug <file.s> --func <name>")
		return 2
	}
	path := fs.Arg(0)

	// Load the kernel to extract function metadata and labels.
	k, err := verify.Load(path)
	if err != nil {
		fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
		return 1
	}
	defer k.Close()

	fl, err := k.Func(*funcName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
		return 1
	}

	// Build the label list for the REPL.
	var labels []debug.Label
	for name, off := range fl.Labels {
		labels = append(labels, debug.Label{Name: name, Offset: off})
	}
	sort.Slice(labels, func(i, j int) bool { return labels[i].Offset < labels[j].Offset })

	// Launch the debuggee with a zeroed argument block.
	argBlock := make([]byte, fl.Args)
	sess, err := debug.Launch("", path, *funcName, argBlock)
	if err != nil {
		fmt.Fprintf(os.Stderr, "gasm debug: %v\n", err)
		return 1
	}
	defer sess.Kill()

	bm := debug.NewBreakpoints(sess)
	fmt.Printf("gasm debug: %s in %s (pid %d)\n", *funcName, path, sess.Pid())

	// Convert the line table for the REPL.
	var srcLines []debug.SourceLine
	for _, le := range fl.Lines {
		srcLines = append(srcLines, debug.SourceLine{Offset: le.Offset, Line: le.Line})
	}
	debug.REPL(sess, bm, sess.CodeBase(), fl.Offset, fl.Size, fl.Args, labels, srcLines)
	return 0
}