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

// Full-screen TUI debugger for Five — Harbour/Clipper debugger style.
// Uses ANSI escape codes for terminal rendering.
// termSize() and readDebugKey() live in termios_<os>.go because their
// low-level mechanics (ioctls vs Windows console API) don't share code.

package hbrt

import (
	"fmt"
	"os"
	"strings"
)

// TUIDebugger creates a full-screen terminal debugger callback.
func TUIDebugger() DebugCallback {
	var sourceCache map[string][]string // file → lines cache
	sourceCache = make(map[string][]string)

	return func(event *DebugEvent) int {
		// Switch to cooked mode for debugger
		restoreCooked()
		defer reenterRaw()

		// Load source file
		srcDir := ""
		if event.Thread.VM().Debugger != nil {
			srcDir = event.Thread.VM().Debugger.SourceDir
		}
		lines := loadSource(sourceCache, event.Module, srcDir)

		// Get terminal size
		rows, cols := termSize()
		if rows < 10 {
			rows = 24
		}
		if cols < 40 {
			cols = 80
		}

		// Layout:
		// Row 1: title bar
		// Row 2 ~ srcEnd: source code
		// srcEnd+1 ~ panelEnd: locals + stack side by side
		// Last row: command bar
		srcHeight := rows - 10
		if srcHeight < 5 {
			srcHeight = 5
		}
		panelHeight := rows - srcHeight - 3 // title + src + cmdbar
		if panelHeight < 3 {
			panelHeight = 3
		}

		for {
			// Clear screen
			fmt.Print("\033[2J\033[H")

			// === Title Bar ===
			title := fmt.Sprintf(" Five Debugger - %s:%d %s() ", event.Module, event.Line, event.Function)
			if event.Reason == "breakpoint" {
				title += "[BREAKPOINT] "
			}
			fmt.Printf("\033[7m%-*s\033[0m\r\n", cols, title)

			// === Source Window ===
			drawSourceWindow(lines, event.Line, srcHeight, cols, event.Thread.VM().Debugger)

			// === Panels: Locals | Call Stack ===
			localW := cols / 2
			stackW := cols - localW
			drawPanels(event, panelHeight, localW, stackW)

			// === Command Bar ===
			fmt.Printf("\033[7m%-*s\033[0m", cols,
				" F5:Go F7:Into F8:Step F9:Break F10:Over F11:Out U:Until :Cmd P:Print W:Watch D:Diag ESC:Quit")

			// Wait for key
			key := readDebugKey()

			switch key {
			case 0x1B, 'q', 'Q': // ESC or Q — quit
				fmt.Print("\033[2J\033[H")
				restoreCooked()
				os.Exit(0)

			case 0xF5, 'g', 'G': // F5 or G — Go/Continue
				return DbgContinue

			case 0xF7: // F7 — Step Into
				return DbgStepLine

			case 0xF8, 's', 'S', 10, 13: // F8 / s / Enter — Step
				return DbgStepLine

			case 0xF9, 'b', 'B': // F9 or B — Toggle Breakpoint
				dbg := event.Thread.VM().Debugger
				found := false
				for i, bp := range dbg.Breakpoints {
					if bp.Line == event.Line {
						dbg.RemoveBreakpoint(i)
						found = true
						break
					}
				}
				if !found {
					dbg.AddBreakpoint(event.Module, event.Line)
				}
				continue // redraw

			case 0xFA, 'n', 'N': // F10 or N — Step Over
				return DbgStepOver

			case 0xFB, 'o', 'O': // F11 or O — Step Out
				return DbgStepOut

			case 'c', 'C': // Continue
				return DbgContinue

			case ':': // Command prompt — any full debugger command
				if mode, ok := runTUIPrompt(event, rows, cols, ""); ok {
					return mode
				}
				continue

			case 'p', 'P': // Quick print prompt — pre-fills "p "
				if mode, ok := runTUIPrompt(event, rows, cols, "p "); ok {
					return mode
				}
				continue

			case 'w': // Add watch — pre-fills "w "
				if mode, ok := runTUIPrompt(event, rows, cols, "w "); ok {
					return mode
				}
				continue

			case 'u', 'U': // Run until line — pre-fills "u "
				if mode, ok := runTUIPrompt(event, rows, cols, "u "); ok {
					return mode
				}
				continue

			case 'W': // Shift-W — clear watches
				event.Thread.VM().Debugger.Watches = nil
				continue

			case 'D', 'd': // D — diagnostics pop-up (workareas + SET + runtime)
				showDiagPopup(event, rows, cols)
				continue

			case 0xE0, 0xE1, 0xE2, 0xE3: // Arrow keys — ignore
				continue

			default:
				continue // unknown key, redraw
			}
		}
	}
}

// runTUIPrompt pops up a bottom-line `:` prompt, reads a command, feeds
// it to runDebugCmd. Returns (mode, true) if the command resumed
// execution (c/s/n/o/u), or (_, false) to stay in the TUI loop.
//
// Captured output is shown on the line above the prompt for a moment
// so the user can see the result before the redraw.
func runTUIPrompt(event *DebugEvent, rows, cols int, prefill string) (int, bool) {
	// Move to the command-bar row, clear it, enter cooked mode for input.
	fmt.Printf("\033[%d;1H\033[2K", rows)
	restoreCooked()
	defer reenterRaw()

	fmt.Printf(":%s", prefill)
	var buf [1024]byte
	reader := os.Stdin
	// Use a fresh read — bufio would complicate the one-shot prompt.
	n, _ := reader.Read(buf[:])
	line := strings.TrimRight(prefill+string(buf[:n]), "\r\n")

	// Capture output so we can show it on the status line.
	var outLines []string
	mode := runDebugCmd(event, line, func(s string) { outLines = append(outLines, s) })

	if len(outLines) > 0 {
		// Print up to 3 output lines above the prompt row — enough for
		// watch listings / breakpoint-set confirmations without
		// obscuring the source view above.
		show := outLines
		if len(show) > 3 {
			show = show[len(show)-3:]
		}
		for i, ln := range show {
			fmt.Printf("\033[%d;1H\033[2K%s", rows-1-len(show)+i+1, ln)
		}
		// Give the user a beat to read, but they can skip with any key.
		readDebugKey()
	}

	return mode, mode != cmdNoMode
}

func drawSourceWindow(lines []string, curLine, height, width int, dbg *Debugger) {
	// Calculate visible range centered on current line
	start := curLine - height/2
	if start < 1 {
		start = 1
	}
	end := start + height - 1
	if end > len(lines) {
		end = len(lines)
	}

	// Top border
	fmt.Printf("\033[36m\u250C\u2500 Source \u2500%s\u2510\033[0m\r\n", strings.Repeat("\u2500", width-12))

	for i := start; i <= end; i++ {
		lineText := ""
		if i-1 < len(lines) {
			lineText = lines[i-1]
		}
		// Truncate to fit
		if len(lineText) > width-10 {
			lineText = lineText[:width-10]
		}

		// Breakpoint marker
		bpMark := " "
		if dbg != nil {
			for _, bp := range dbg.Breakpoints {
				if bp.Enabled && bp.Line == i {
					bpMark = "\033[31m\u25CF\033[0m" // red dot
					break
				}
			}
		}

		// Current line marker
		if i == curLine {
			fmt.Printf("\033[36m\u2502\033[0m%s\033[33m>> %4d:\033[0m \033[7m%-*s\033[0m\033[36m\u2502\033[0m\r\n",
				bpMark, i, width-10, lineText)
		} else {
			fmt.Printf("\033[36m\u2502\033[0m%s   %4d: %-*s\033[36m\u2502\033[0m\r\n",
				bpMark, i, width-10, lineText)
		}
	}

	// Pad remaining lines
	for i := end - start + 1; i < height; i++ {
		fmt.Printf("\033[36m\u2502\033[0m%*s\033[36m\u2502\033[0m\r\n", width-2, "")
	}

	// Bottom border
	fmt.Printf("\033[36m\u2514%s\u2518\033[0m\r\n", strings.Repeat("\u2500", width-2))
}

func drawPanels(event *DebugEvent, height, localW, rightW int) {
	// The right column splits vertically into Stack (top) and Watches
	// (bottom). Split 50/50 but give watches at least 3 rows once any
	// exist, else hand the whole column to stack.
	dbg := event.Thread.VM().Debugger
	nWatches := 0
	if dbg != nil {
		nWatches = len(dbg.Watches)
	}
	contentRows := height - 2 // minus header+footer borders on each side
	stackRows := contentRows
	watchRows := 0
	if nWatches > 0 {
		watchRows = contentRows / 2
		if watchRows < 3 {
			watchRows = 3
		}
		if watchRows > contentRows-2 {
			watchRows = contentRows - 2
		}
		stackRows = contentRows - watchRows - 1 // -1 for the divider
	}

	// Pre-render rendered watch lines (outside the row loop so we don't
	// re-evaluate expressions per row).
	watchLines := make([]string, 0, nWatches)
	if nWatches > 0 {
		for i, expr := range dbg.Watches {
			v, evalErr := event.Thread.EvalWithFrameLocals(expr)
			var rendered string
			if evalErr != "" {
				rendered = fmt.Sprintf(" [%d] %s ! %s", i, expr, truncFit(evalErr, 20))
			} else {
				rendered = fmt.Sprintf(" [%d] %s = %s", i, expr, describeDbgValue(v))
			}
			watchLines = append(watchLines, rendered)
		}
	}

	// Headers
	localHeader := fmt.Sprintf("\u250C\u2500 Locals %s\u2510", strings.Repeat("\u2500", localW-11))
	stackHeader := fmt.Sprintf("\u250C\u2500 Stack %s\u2510", strings.Repeat("\u2500", rightW-10))
	fmt.Printf("\033[36m%s%s\033[0m\r\n", localHeader, stackHeader)

	// Body rows — left is always locals, right alternates Stack then
	// (optional) Watches, separated by a mid-panel header.
	for i := 0; i < contentRows; i++ {
		localLine := ""
		if i < len(event.Locals) {
			v := event.Locals[i]
			val := describeDbgValue(v.Value)
			localLine = truncFit(fmt.Sprintf(" %s = %s", v.Name, val), localW-2)
		}

		rightLine := ""
		switch {
		case i < stackRows:
			if i < len(event.CallStack) {
				f := event.CallStack[i]
				if f.Module != "" {
					rightLine = fmt.Sprintf(" %s() %s:%d", f.Function, f.Module, f.Line)
				} else {
					rightLine = fmt.Sprintf(" %s()", f.Function)
				}
			}
		case i == stackRows && watchRows > 0:
			// Mid-panel divider/header for the Watches sub-section.
			rightLine = "─ Watches " + strings.Repeat("─", rightW-13)
		default:
			widx := i - stackRows - 1
			if widx >= 0 && widx < len(watchLines) {
				rightLine = watchLines[widx]
			}
		}
		rightLine = truncFit(rightLine, rightW-2)

		fmt.Printf("\033[36m\u2502\033[0m%s\033[36m\u2502\033[0m%s\033[36m\u2502\033[0m\r\n",
			padRunes(localLine, localW-2), padRunes(rightLine, rightW-2))
	}

	// Bottom borders
	localFooter := fmt.Sprintf("\u2514%s\u2518", strings.Repeat("\u2500", localW-2))
	stackFooter := fmt.Sprintf("\u2514%s\u2518", strings.Repeat("\u2500", rightW-2))
	fmt.Printf("\033[36m%s%s\033[0m\r\n", localFooter, stackFooter)
}

// showDiagPopup renders the full diagnostic dump (workareas, SET flags,
// runtime) in a scrollable bottom panel. Press any key to dismiss.
// Reuses DebugDiagnosticHook so output matches error.log exactly.
func showDiagPopup(event *DebugEvent, rows, cols int) {
	if DebugDiagnosticHook == nil {
		return
	}
	var lines []string
	DebugDiagnosticHook(event.Thread, "", func(s string) {
		for _, ln := range strings.Split(s, "\n") {
			if ln != "" {
				lines = append(lines, ln)
			}
		}
	})

	// Clear and redraw as a full-screen scrolling view. Simplest: clear
	// screen, print lines, show a "-- press any key --" footer.
	start := 0
	for {
		fmt.Print("\033[2J\033[H")
		fmt.Printf("\033[7m%s\033[0m\r\n", padRunes(" Diagnostics (q/ESC to close, space/pgdn next, pgup prev) ", cols))

		viewH := rows - 2
		end := start + viewH
		if end > len(lines) {
			end = len(lines)
		}
		for i := start; i < end; i++ {
			fmt.Printf("%s\r\n", truncFit(lines[i], cols))
		}
		// Pad remaining rows
		for i := end - start; i < viewH; i++ {
			fmt.Print("\r\n")
		}
		fmt.Printf("\033[7m%s\033[0m", padRunes(
			fmt.Sprintf(" line %d-%d of %d ", start+1, end, len(lines)), cols))

		key := readDebugKey()
		switch key {
		case 0x1B, 'q', 'Q':
			return
		case ' ', 10, 13, 0xE1: // space / enter / down-arrow
			start += viewH
			if start >= len(lines) {
				start = len(lines) - 1
			}
		case 'b', 'B', 0xE0: // back page / up-arrow
			start -= viewH
			if start < 0 {
				start = 0
			}
		default:
			return
		}
	}
}

// padRunes right-pads s with spaces so its display width is `width`
// runes. Used instead of Printf's "%-*s" which counts bytes, mangling
// UTF-8 box-drawing / CJK. Assumes each rune is one display column —
// not strictly true for CJK "wide" chars, but good enough for the
// Latin/box-drawing mix this debugger prints.
func padRunes(s string, width int) string {
	runes := []rune(s)
	if len(runes) >= width {
		return string(runes[:width])
	}
	return s + strings.Repeat(" ", width-len(runes))
}

// truncFit clamps s to at most width runes, appending "…" on truncation.
// Rune-aware so it doesn't cut UTF-8 box-drawing / CJK characters in
// the middle of a multi-byte sequence (which would render as mojibake).
func truncFit(s string, width int) string {
	if width <= 0 {
		return ""
	}
	runes := []rune(s)
	if len(runes) <= width {
		return s
	}
	if width <= 1 {
		return string(runes[:width])
	}
	return string(runes[:width-1]) + "…"
}

func loadSource(cache map[string][]string, filename string, sourceDir string) []string {
	if lines, ok := cache[filename]; ok {
		return lines
	}

	// Try as-is first
	data, err := os.ReadFile(filename)
	if err != nil && sourceDir != "" {
		// Try relative to source directory
		joined := sourceDir + "/" + filename
		data, err = os.ReadFile(joined)
		if err != nil {
			// Try just the basename in source dir
			base := filename
			if idx := strings.LastIndexAny(filename, "/\\"); idx >= 0 {
				base = filename[idx+1:]
			}
			data, err = os.ReadFile(sourceDir + "/" + base)
		}
	}
	if err != nil {
		return []string{"(source not available: " + filename + ")"}
	}
	lines := strings.Split(string(data), "\n")
	cache[filename] = lines
	return lines
}

// termSize() and readDebugKey() moved to termios_<os>.go — the Unix
// implementations use ioctl TIOCGWINSZ + raw-mode termios, while the
// Windows version uses console APIs.