//go:build !windows

// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// Interactive CLI debugger for Five.
// Provides a gdb-like command interface for stepping through PRG code.
//
// Commands:
//   s, step     — step to next line
//   n, next     — step over (don't enter functions)
//   o, out      — step out of current function
//   c, cont     — continue (run until breakpoint)
//   b <line>    — set breakpoint at line
//   d <n>       — delete breakpoint
//   bl          — list breakpoints
//   p <expr>    — print variable value
//   l           — list locals
//   bt          — show call stack (backtrace)
//   q           — quit
//   h           — help

package hbrt

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	"syscall"
	"unsafe"
)

// Terminal mode helpers — restore cooked mode for debugger, re-enter raw for program
var savedTermios syscall.Termios
var termSaved bool

func restoreCooked() {
	fd := int(os.Stdin.Fd())
	var t syscall.Termios
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5401, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
	if !termSaved {
		savedTermios = t
		termSaved = true
	}
	// Set cooked mode
	t.Lflag |= syscall.ICANON | syscall.ECHO
	t.Oflag |= syscall.OPOST
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5402, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
}

func reenterRaw() {
	fd := int(os.Stdin.Fd())
	var t syscall.Termios
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5401, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
	t.Lflag &^= syscall.ICANON | syscall.ECHO | syscall.ISIG
	t.Oflag &^= syscall.OPOST
	t.Cc[syscall.VMIN] = 1
	t.Cc[syscall.VTIME] = 0
	syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), 0x5402, uintptr(unsafe.Pointer(&t)), 0, 0, 0)
}

// CLIDebugger creates a DebugCallback for interactive terminal debugging.
func CLIDebugger() DebugCallback {
	reader := bufio.NewReader(os.Stdin)
	lastCmd := "s" // default repeat command

	return func(event *DebugEvent) int {
		// Restore terminal to cooked mode for debugger I/O
		fmt.Print("\r\n")
		restoreCooked()
		defer reenterRaw()

		if event.Reason == "breakpoint" {
			fmt.Printf("  ** Breakpoint at %s:%d\n", event.Module, event.Line)
		}
		fmt.Printf("  %s:%d in %s()\n", event.Module, event.Line, event.Function)

		// Show source line if available
		showSourceLine(event.Module, event.Line)

		for {
			fmt.Printf("(dbg) ")
			line, err := reader.ReadString('\n')
			if err != nil {
				return DbgContinue
			}
			line = strings.TrimSpace(line)
			if line == "" {
				line = lastCmd // repeat last command
			} else {
				lastCmd = line
			}

			parts := strings.Fields(line)
			cmd := parts[0]

			switch cmd {
			case "s", "step":
				return DbgStepLine

			case "n", "next":
				return DbgStepOver

			case "o", "out":
				return DbgStepOut

			case "c", "cont", "continue":
				return DbgContinue

			case "b", "break":
				if len(parts) >= 2 {
					lineNo, err := strconv.Atoi(parts[1])
					if err == nil {
						mod := event.Module
						if len(parts) >= 3 {
							mod = parts[2]
						}
						dbg := event.Thread.VM().Debugger
						idx := dbg.AddBreakpoint(mod, lineNo)
						fmt.Printf("  Breakpoint %d at %s:%d\n", idx, mod, lineNo)
					} else {
						fmt.Println("  Usage: b <line> [module]")
					}
				} else {
					fmt.Println("  Usage: b <line> [module]")
				}

			case "d", "del", "delete":
				if len(parts) >= 2 {
					idx, err := strconv.Atoi(parts[1])
					if err == nil {
						event.Thread.VM().Debugger.RemoveBreakpoint(idx)
						fmt.Printf("  Breakpoint %d removed\n", idx)
					}
				} else {
					fmt.Println("  Usage: d <breakpoint_number>")
				}

			case "bl", "breakpoints":
				dbg := event.Thread.VM().Debugger
				if len(dbg.Breakpoints) == 0 {
					fmt.Println("  No breakpoints")
				} else {
					for i, bp := range dbg.Breakpoints {
						status := "ON "
						if !bp.Enabled {
							status = "OFF"
						}
						fmt.Printf("  %d: [%s] %s:%d (hits: %d)\n", i, status, bp.Module, bp.Line, bp.HitCount)
					}
				}

			case "l", "locals":
				if len(event.Locals) == 0 {
					fmt.Println("  No local variables")
				} else {
					for _, v := range event.Locals {
						fmt.Printf("  %s [%s] %s = %s\n", v.Scope, fmt.Sprintf("%d", v.Index), v.Name, v.Value.String())
					}
				}

			case "p", "print":
				if len(parts) >= 2 {
					varName := parts[1]
					found := false
					for _, v := range event.Locals {
						if strings.EqualFold(v.Name, varName) || fmt.Sprintf("_%d", v.Index) == varName {
							fmt.Printf("  %s = %s\n", v.Name, v.Value.String())
							found = true
							break
						}
					}
					if !found {
						// Try by index
						idx, err := strconv.Atoi(varName)
						if err == nil && idx >= 1 && idx <= len(event.Locals) {
							v := event.Locals[idx-1]
							fmt.Printf("  %s = %s\n", v.Name, v.Value.String())
						} else {
							fmt.Printf("  Variable '%s' not found\n", varName)
						}
					}
				} else {
					fmt.Println("  Usage: p <varname|index>")
				}

			case "bt", "backtrace", "stack":
				if len(event.CallStack) == 0 {
					fmt.Println("  Empty call stack")
				} else {
					for i, frame := range event.CallStack {
						marker := "  "
						if i == 0 {
							marker = "=>"
						}
						if frame.Module != "" {
							fmt.Printf("  %s #%d %s() at %s:%d\n", marker, frame.Level, frame.Function, frame.Module, frame.Line)
						} else {
							fmt.Printf("  %s #%d %s()\n", marker, frame.Level, frame.Function)
						}
					}
				}

			case "q", "quit":
				fmt.Println("  Debugger quit.")
				os.Exit(0)

			case "h", "help", "?":
				fmt.Println("  Five Debugger Commands:")
				fmt.Println("    s, step      — step to next line")
				fmt.Println("    n, next      — step over function calls")
				fmt.Println("    o, out       — step out of current function")
				fmt.Println("    c, cont      — continue (run to next breakpoint)")
				fmt.Println("    b <line>     — set breakpoint at line")
				fmt.Println("    d <n>        — delete breakpoint n")
				fmt.Println("    bl           — list all breakpoints")
				fmt.Println("    l            — show local variables")
				fmt.Println("    p <var>      — print variable value")
				fmt.Println("    bt           — show call stack")
				fmt.Println("    q            — quit")

			default:
				fmt.Printf("  Unknown command: %s (type 'h' for help)\n", cmd)
			}
		}
	}
}

// showSourceLine attempts to show the source code around the current line.
func showSourceLine(module string, line int) {
	data, err := os.ReadFile(module)
	if err != nil {
		return
	}
	lines := strings.Split(string(data), "\n")
	start := line - 3
	if start < 1 {
		start = 1
	}
	end := line + 2
	if end > len(lines) {
		end = len(lines)
	}
	for i := start; i <= end; i++ {
		marker := "  "
		if i == line {
			marker = ">>"
		}
		if i-1 < len(lines) {
			fmt.Printf("  %s %4d: %s\n", marker, i, lines[i-1])
		}
	}
}