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

// Shared debugger command dispatch. Both the CLI (gdb-style prompt)
// and the TUI (full-screen F-keys + `:` prompt) funnel parsed input
// strings through runDebugCmd so the surface area stays in one place.

package hbrt

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

// cmdNoMode is the sentinel returned by runDebugCmd when a command
// printed output and the debug loop should keep prompting — i.e. no
// mode transition is requested.
const cmdNoMode = -1

// runDebugCmd interprets one line of debugger input against the given
// event. Returns a DbgContinue / DbgStepLine / ... constant when the
// command resumes execution, or cmdNoMode to stay in the prompt loop.
// Prints results/errors using the supplied `out` writer so the TUI can
// buffer them for its status area while the CLI writes to stdout.
func runDebugCmd(event *DebugEvent, line string, out func(string)) int {
	line = strings.TrimSpace(line)
	if line == "" {
		return cmdNoMode
	}
	if out == nil {
		out = func(s string) { fmt.Println(s) }
	}

	parts := strings.Fields(line)
	cmd := parts[0]
	dbg := event.Thread.VM().Debugger

	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":
		mod, lineNo, cond, ok := parseBreakArgs(line, parts, event.Module)
		if !ok {
			out("  Usage: b <line> [module] [if <expr>]")
			return cmdNoMode
		}
		idx := dbg.AddBreakpoint(mod, lineNo)
		if cond != "" {
			dbg.Breakpoints[idx].Condition = cond
			out(fmt.Sprintf("  Breakpoint %d at %s:%d if %s", idx, mod, lineNo, cond))
		} else {
			out(fmt.Sprintf("  Breakpoint %d at %s:%d", idx, mod, lineNo))
		}

	case "u", "until":
		if len(parts) >= 2 {
			if lineNo, err := strconv.Atoi(parts[1]); err == nil && lineNo > 0 {
				dbg.ToCursorMod = event.Module
				dbg.ToCursorLine = lineNo
				if len(parts) >= 3 {
					dbg.ToCursorMod = parts[2]
				}
				return DbgToCursor
			}
		}
		out("  Usage: u <line> [module]")

	case "w", "watch":
		if len(parts) < 2 {
			if len(dbg.Watches) == 0 {
				out("  No watches. Usage: w <expr>")
			} else {
				for i, e := range dbg.Watches {
					out(fmt.Sprintf("  [%d] %s", i, e))
				}
			}
			return cmdNoMode
		}
		expr := strings.TrimSpace(line[len(parts[0]):])
		dbg.Watches = append(dbg.Watches, expr)
		out(fmt.Sprintf("  Watch %d: %s", len(dbg.Watches)-1, expr))

	case "wd", "unwatch":
		if len(parts) >= 2 {
			if idx, err := strconv.Atoi(parts[1]); err == nil {
				if idx >= 0 && idx < len(dbg.Watches) {
					dbg.Watches = append(dbg.Watches[:idx], dbg.Watches[idx+1:]...)
					out(fmt.Sprintf("  Watch %d removed", idx))
					return cmdNoMode
				}
			}
		}
		out("  Usage: wd <watch_number>")

	case "d", "del", "delete":
		if len(parts) >= 2 {
			if idx, err := strconv.Atoi(parts[1]); err == nil {
				dbg.RemoveBreakpoint(idx)
				out(fmt.Sprintf("  Breakpoint %d removed", idx))
				return cmdNoMode
			}
		}
		out("  Usage: d <breakpoint_number>")

	case "bl", "breakpoints":
		if len(dbg.Breakpoints) == 0 {
			out("  No breakpoints")
		} else {
			for i, bp := range dbg.Breakpoints {
				status := "ON "
				if !bp.Enabled {
					status = "OFF"
				}
				cond := ""
				if bp.Condition != "" {
					cond = "  if " + bp.Condition
				}
				out(fmt.Sprintf("  %d: [%s] %s:%d%s  (hits: %d)",
					i, status, bp.Module, bp.Line, cond, bp.HitCount))
			}
		}

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

	case "p", "print":
		if len(parts) < 2 {
			out("  Usage: p <expr>")
			return cmdNoMode
		}
		expr := strings.TrimSpace(line[len(parts[0]):])
		v, evalErr := event.Thread.EvalWithFrameLocals(expr)
		if evalErr != "" {
			out(fmt.Sprintf("  eval failed: %s", evalErr))
		} else {
			out(fmt.Sprintf("  %s = %s", expr, describeDbgValue(v)))
		}

	case "diag", "d!":
		// Full error.log-style dump at the break point — workareas,
		// SET flags, runtime memory. Same renderer our DefaultErrorHook
		// uses, so what you see here is what you'd get if the program
		// had crashed instead of stopped.
		if DebugDiagnosticHook == nil {
			out("  (diagnostics unavailable — hook not installed)")
		} else {
			DebugDiagnosticHook(event.Thread, "", func(s string) {
				for _, ln := range strings.Split(s, "\n") {
					if ln != "" {
						out(ln)
					}
				}
			})
		}

	case "wa", "workareas":
		if DebugDiagnosticHook == nil {
			out("  (workarea info unavailable)")
		} else {
			DebugDiagnosticHook(event.Thread, "wa", func(s string) {
				for _, ln := range strings.Split(s, "\n") {
					if ln != "" {
						out(ln)
					}
				}
			})
		}

	case "set":
		if DebugDiagnosticHook == nil {
			out("  (SET state unavailable)")
		} else {
			DebugDiagnosticHook(event.Thread, "set", func(s string) {
				for _, ln := range strings.Split(s, "\n") {
					if ln != "" {
						out(ln)
					}
				}
			})
		}

	case "mem":
		if DebugDiagnosticHook == nil {
			out("  (memory stats unavailable)")
		} else {
			DebugDiagnosticHook(event.Thread, "mem", func(s string) {
				for _, ln := range strings.Split(s, "\n") {
					if ln != "" {
						out(ln)
					}
				}
			})
		}

	case "hist", "trace":
		// Execution trace — last N PRG lines the current thread stepped
		// through. Most useful for "how did control reach here?" when
		// you break inside a deeply-nested helper and want to see the
		// LOOP/IF/Call chain that led to it. Deduplicates adjacent
		// repeats (tight FOR loops compress to "line X ×27") so the
		// output stays readable in hot code.
		trace, total := event.Thread.Trace()
		if len(trace) == 0 {
			out("  (no trace data — debugger just attached?)")
			return cmdNoMode
		}
		// How many to show — default 50, or "hist N"
		limit := 50
		if len(parts) >= 2 {
			if n, err := strconv.Atoi(parts[1]); err == nil && n > 0 {
				limit = n
			}
		}
		if limit > len(trace) {
			limit = len(trace)
		}
		view := trace[len(trace)-limit:]
		// Collapse adjacent duplicates.
		type run struct {
			e     TraceEntry
			count int
		}
		var runs []run
		for _, e := range view {
			if n := len(runs); n > 0 && runs[n-1].e == e {
				runs[n-1].count++
				continue
			}
			runs = append(runs, run{e, 1})
		}
		out(fmt.Sprintf("  trace (last %d of %d) — newest last:", len(view), total))
		for _, r := range runs {
			suffix := ""
			if r.count > 1 {
				suffix = fmt.Sprintf("  ×%d", r.count)
			}
			out(fmt.Sprintf("    %s:%d%s", r.e.Module, r.e.Line, suffix))
		}

	case "threads", "ts":
		// Lists every live Thread managed by the VM with its current
		// PRG source position. Useful for diagnosing multi-thread PRG
		// programs (hb_Thread*, GoLaunch) where the debugger is
		// currently attached to one thread but others may be blocked,
		// looping, or crashed. Position is read from each thread's
		// current frame — may show an older line for threads that
		// haven't executed a DebugLine recently.
		threads := event.Thread.VM().Threads()
		if len(threads) == 0 {
			out("  (no threads tracked)")
			return cmdNoMode
		}
		for _, th := range threads {
			marker := "  "
			if th == event.Thread {
				marker = "=>"
			}
			mod, line := "", 0
			if f := th.CurFrame(); f != nil {
				mod = f.module
				line = f.line
			}
			name := "MAIN"
			if f := th.CurFrame(); f != nil && f.symbol != nil {
				name = f.symbol.Name
			}
			if mod == "" {
				out(fmt.Sprintf("  %s [%d] %s", marker, th.TID(), name))
			} else {
				out(fmt.Sprintf("  %s [%d] %s  at %s:%d",
					marker, th.TID(), name, mod, line))
			}
		}

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

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

	case "h", "help", "?":
		for _, ln := range debugCmdHelp {
			out(ln)
		}

	default:
		out(fmt.Sprintf("  Unknown command: %s (type 'h' for help)", cmd))
	}
	return cmdNoMode
}

var debugCmdHelp = []string{
	"  Five Debugger Commands:",
	"    s, step           — step to next line",
	"    n, next           — step over function calls",
	"    o, out            — step out of current function",
	"    c, cont           — continue (run to next breakpoint)",
	"    u <line>          — run until <line> in current module",
	"    b <line> [if E]   — set breakpoint, optional condition",
	"    d <n>             — delete breakpoint n",
	"    bl                — list all breakpoints",
	"    w <expr>          — add watch expression",
	"    wd <n>            — remove watch n",
	"    w                 — list watches",
	"    l                 — show local variables",
	"    p <expr>          — evaluate and print expression",
	"    bt                — show call stack",
	"    wa                — list open workareas + active index",
	"    set               — SET state (DELETED, DATEFORMAT, ...)",
	"    mem               — runtime memory / GC stats",
	"    diag              — full diag dump (wa + set + mem)",
	"    threads, ts       — list all live threads",
	"    hist, trace [N]   — last N lines executed (how did we get here?)",
	"    q                 — quit",
}

// describeDbgValue is now shared across platforms. It lives in
// debugcmd.go because debugcli.go is !windows-only and runDebugCmd
// needs this regardless of platform.
func describeDbgValue(v Value) string {
	switch {
	case v.IsNil():
		return "NIL"
	case v.IsString():
		return fmt.Sprintf("%q", v.AsString())
	}
	return v.String()
}

// parseBreakArgs accepts:
//
//	b <line>
//	b <line> <module>
//	b <line> if <expr>
//	b <line> <module> if <expr>
func parseBreakArgs(rawLine string, parts []string, defaultMod string) (module string, line int, cond string, ok bool) {
	if len(parts) < 2 {
		return "", 0, "", false
	}
	lineNo, err := strconv.Atoi(parts[1])
	if err != nil || lineNo <= 0 {
		return "", 0, "", false
	}
	module = defaultMod
	lowered := strings.ToLower(rawLine)
	if idx := strings.Index(lowered, " if "); idx > 0 {
		cond = strings.TrimSpace(rawLine[idx+4:])
		rawLine = rawLine[:idx]
		parts = strings.Fields(rawLine)
	}
	if len(parts) >= 3 {
		module = parts[2]
	}
	return module, lineNo, cond, true
}