package dev

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"syscall"
	"testing"
	"time"

	"git.golem15.com/golem15/summercms/internal/build"
	"git.golem15.com/golem15/summercms/modules/bonfire"
)

type safeBuffer struct {
	mu sync.Mutex
	b  bytes.Buffer
}

func (s *safeBuffer) Write(p []byte) (int, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.b.Write(p)
}

func (s *safeBuffer) String() string {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.b.String()
}

// testOutput is a non-terminal bonfire console writing to w.
func testOutput(w io.Writer) bonfire.Output {
	return bonfire.NewOutput(strings.NewReader(""), w, w)
}

func TestWatchRebuildsOnSourceEdit(t *testing.T) {
	dir := t.TempDir()
	writeWatchApp(t, dir)

	var out safeBuffer
	var builds atomic.Int32
	var starts atomic.Int32

	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()

	opts := Options{
		Debounce: 40 * time.Millisecond,
		Build: func(ctx context.Context, appDir string, w io.Writer) error {
			builds.Add(1)
			fmt.Fprintln(w, "built hello in 1ms")
			return nil
		},
		Start: func(ctx context.Context, binPath string, args []string, stdout, stderr io.Writer) (*exec.Cmd, error) {
			if got := strings.Join(args, " "); got != "serve -v --env staging" {
				return nil, fmt.Errorf("start args = %q, want serve and the forwarded globals", got)
			}
			starts.Add(1)
			cmd := exec.Command("sleep", "30")
			if err := cmd.Start(); err != nil {
				return nil, err
			}
			return cmd, nil
		},
	}

	done := make(chan error, 1)
	go func() { done <- watch(ctx, dir, testOutput(&out), []string{"-v", "--env", "staging"}, opts) }()

	waitUntil(t, "initial start", func() bool { return starts.Load() == 1 })
	if builds.Load() != 1 {
		t.Fatalf("initial builds = %d", builds.Load())
	}

	if err := os.WriteFile(filepath.Join(dir, "plugin.go"), []byte("package p\n// edited\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	waitUntil(t, "restart after edit", func() bool { return starts.Load() == 2 })
	if builds.Load() != 2 {
		t.Fatalf("builds after edit = %d", builds.Load())
	}

	if err := os.WriteFile(filepath.Join(dir, "plugins.gen.go"), []byte("package main\n// generated\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte("package main\n// generated\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	time.Sleep(200 * time.Millisecond)
	if starts.Load() != 2 || builds.Load() != 2 {
		t.Fatalf("generated files triggered rebuild starts=%d builds=%d", starts.Load(), builds.Load())
	}

	got := out.String()
	if strings.Count(got, "Rebuilt in ") != 2 {
		t.Fatalf("want 2 rebuild latency lines, got %q", got)
	}

	cancel()
	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("watch returned %v after Ctrl+C, want nil (exit 0)", err)
		}
		if !strings.Contains(out.String(), "Dev report") || !strings.Contains(out.String(), "Restarts  1") {
			t.Fatalf("missing dev report:\n%s", out.String())
		}
	case <-time.After(3 * time.Second):
		t.Fatal("watch did not exit on cancel")
	}
}

func TestWatchKeepsChildOnBuildFailure(t *testing.T) {
	dir := t.TempDir()
	writeWatchApp(t, dir)

	var out safeBuffer
	var builds atomic.Int32
	var starts atomic.Int32
	var pid atomic.Int32

	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()

	opts := Options{
		Debounce: 40 * time.Millisecond,
		Build: func(ctx context.Context, appDir string, w io.Writer) error {
			n := builds.Add(1)
			if n >= 2 {
				return fmt.Errorf("compile failed")
			}
			return nil
		},
		Start: func(ctx context.Context, binPath string, args []string, stdout, stderr io.Writer) (*exec.Cmd, error) {
			starts.Add(1)
			cmd := exec.Command("sleep", "30")
			if err := cmd.Start(); err != nil {
				return nil, err
			}
			pid.Store(int32(cmd.Process.Pid))
			return cmd, nil
		},
	}

	done := make(chan error, 1)
	go func() { done <- watch(ctx, dir, testOutput(&out), nil, opts) }()
	waitUntil(t, "initial start", func() bool { return starts.Load() == 1 })

	if err := os.WriteFile(filepath.Join(dir, "plugin.go"), []byte("package p\n// bad\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	waitUntil(t, "failed rebuild", func() bool { return builds.Load() >= 2 })
	time.Sleep(80 * time.Millisecond)
	if starts.Load() != 1 {
		t.Fatalf("build failure restarted child: starts=%d", starts.Load())
	}
	if !strings.Contains(out.String(), "compile failed") {
		t.Fatalf("missing build error: %s", out.String())
	}
	proc, err := os.FindProcess(int(pid.Load()))
	if err != nil {
		t.Fatal(err)
	}
	if err := proc.Signal(syscall.Signal(0)); err != nil {
		t.Fatalf("child was reaped after failed build: %v", err)
	}

	cancel()
	select {
	case <-done:
	case <-time.After(3 * time.Second):
		t.Fatal("watch did not exit")
	}
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if err := proc.Signal(syscall.Signal(0)); err != nil {
			return
		}
		time.Sleep(20 * time.Millisecond)
	}
	t.Fatal("child still running after cancel")
}

func TestWatchDebouncesRapidEdits(t *testing.T) {
	dir := t.TempDir()
	writeWatchApp(t, dir)

	var out safeBuffer
	var builds atomic.Int32
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()

	opts := Options{
		Debounce: 80 * time.Millisecond,
		Build: func(ctx context.Context, appDir string, w io.Writer) error {
			builds.Add(1)
			return nil
		},
		Start: func(ctx context.Context, binPath string, args []string, stdout, stderr io.Writer) (*exec.Cmd, error) {
			cmd := exec.Command("sleep", "30")
			if err := cmd.Start(); err != nil {
				return nil, err
			}
			return cmd, nil
		},
	}
	done := make(chan error, 1)
	go func() { done <- watch(ctx, dir, testOutput(&out), nil, opts) }()
	waitUntil(t, "initial build", func() bool { return builds.Load() == 1 })

	for i := 0; i < 5; i++ {
		if err := os.WriteFile(filepath.Join(dir, "plugin.go"), []byte(fmt.Sprintf("package p\n// %d\n", i)), 0o644); err != nil {
			t.Fatal(err)
		}
		time.Sleep(10 * time.Millisecond)
	}
	waitUntil(t, "debounced rebuild", func() bool { return builds.Load() >= 2 })
	time.Sleep(150 * time.Millisecond)
	if builds.Load() != 2 {
		t.Fatalf("rapid edits should coalesce, builds=%d", builds.Load())
	}
	cancel()
	select {
	case <-done:
	case <-time.After(3 * time.Second):
		t.Fatal("watch did not exit")
	}
}

func TestWatchIgnoresBinAndTmp(t *testing.T) {
	dir := t.TempDir()
	writeWatchApp(t, dir)
	if err := os.MkdirAll(filepath.Join(dir, "bin"), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(filepath.Join(dir, "tmp"), 0o755); err != nil {
		t.Fatal(err)
	}

	var out safeBuffer
	var builds atomic.Int32
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()
	opts := Options{
		Debounce: 40 * time.Millisecond,
		Build: func(ctx context.Context, appDir string, w io.Writer) error {
			builds.Add(1)
			return nil
		},
		Start: func(ctx context.Context, binPath string, args []string, stdout, stderr io.Writer) (*exec.Cmd, error) {
			cmd := exec.Command("sleep", "30")
			if err := cmd.Start(); err != nil {
				return nil, err
			}
			return cmd, nil
		},
	}
	done := make(chan error, 1)
	go func() { done <- watch(ctx, dir, testOutput(&out), nil, opts) }()
	waitUntil(t, "initial build", func() bool { return builds.Load() == 1 })

	if err := os.WriteFile(filepath.Join(dir, "bin", "hello.go"), []byte("package main\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dir, "tmp", "scratch.go"), []byte("package tmp\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	time.Sleep(200 * time.Millisecond)
	if builds.Load() != 1 {
		t.Fatalf("bin/tmp edits triggered rebuild: builds=%d", builds.Load())
	}
	cancel()
	select {
	case <-done:
	case <-time.After(3 * time.Second):
		t.Fatal("watch did not exit")
	}
}

func TestWatchHelloWorkspaceRebuildLatency(t *testing.T) {
	dir := copyHelloApp(t)
	var out safeBuffer
	var builds atomic.Int32
	var starts atomic.Int32
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()

	opts := Options{
		Debounce: 80 * time.Millisecond,
		Build: func(ctx context.Context, appDir string, w io.Writer) error {
			builds.Add(1)
			if err := build.App(ctx, appDir, w); err != nil {
				return err
			}
			return nil
		},
		Start: func(ctx context.Context, binPath string, args []string, stdout, stderr io.Writer) (*exec.Cmd, error) {
			starts.Add(1)
			cmd := exec.Command("sleep", "30")
			if err := cmd.Start(); err != nil {
				return nil, err
			}
			return cmd, nil
		},
	}

	done := make(chan error, 1)
	go func() { done <- watch(ctx, dir, testOutput(&out), nil, opts) }()
	waitUntilTimeout(t, 60*time.Second, "initial real rebuild", func() bool { return starts.Load() == 1 })
	if builds.Load() != 1 {
		t.Fatalf("initial builds = %d", builds.Load())
	}
	if !rebuildLinePresent(out.String()) {
		t.Fatalf("missing rebuild latency line after initial build:\n%s", out.String())
	}

	plugin := filepath.Join(dir, "plugins", "greeter", "plugin.go")
	src, err := os.ReadFile(plugin)
	if err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(plugin, append(src, []byte("\n// watch-edit\n")...), 0o644); err != nil {
		t.Fatal(err)
	}
	waitUntilTimeout(t, 60*time.Second, "rebuild after source edit", func() bool { return starts.Load() == 2 })
	got := out.String()
	if strings.Count(got, "Rebuilt in ") < 2 {
		t.Fatalf("want rebuild latency lines after restart, got %q", got)
	}
	if !rebuildLinePresent(got) {
		t.Fatalf("rebuild line missing duration:\n%s", got)
	}

	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte("package main\n// generated\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dir, "plugins.gen.go"), []byte("package main\n// generated\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	time.Sleep(400 * time.Millisecond)
	if starts.Load() != 2 || builds.Load() != 2 {
		t.Fatalf("generated-file edits looped: starts=%d builds=%d", starts.Load(), builds.Load())
	}

	cancel()
	select {
	case err := <-done:
		if err != nil && err != context.Canceled {
			t.Fatalf("watch exit: %v", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("watch did not exit on cancel")
	}
}

func rebuildLinePresent(s string) bool {
	for _, line := range strings.Split(s, "\n") {
		line = strings.TrimSpace(line)
		if _, d, ok := strings.Cut(line, "Rebuilt in "); ok && strings.TrimSpace(d) != "" {
			return true
		}
	}
	return false
}

func waitUntilTimeout(t *testing.T, d time.Duration, name string, ok func() bool) {
	t.Helper()
	deadline := time.Now().Add(d)
	for time.Now().Before(deadline) {
		if ok() {
			return
		}
		time.Sleep(25 * time.Millisecond)
	}
	t.Fatalf("timed out waiting for %s", name)
}

func copyHelloApp(t *testing.T) string {
	t.Helper()
	src, err := filepath.Abs(filepath.Join("..", "..", "examples", "hello"))
	if err != nil {
		t.Fatal(err)
	}
	framework, err := filepath.Abs(filepath.Join("..", ".."))
	if err != nil {
		t.Fatal(err)
	}
	dst := t.TempDir()
	if err := filepath.WalkDir(src, func(path string, d os.DirEntry, err error) error {
		if err != nil {
			return err
		}
		rel, err := filepath.Rel(src, path)
		if err != nil {
			return err
		}
		if rel == "bin" || strings.HasPrefix(rel, "bin"+string(os.PathSeparator)) {
			if d.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}
		target := filepath.Join(dst, rel)
		if d.IsDir() {
			return os.MkdirAll(target, 0o755)
		}
		data, err := os.ReadFile(path)
		if err != nil {
			return err
		}
		if filepath.Base(path) == "go.mod" {
			data = rewriteFrameworkReplace(data, framework)
		}
		if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
			return err
		}
		return os.WriteFile(target, data, 0o644)
	}); err != nil {
		t.Fatal(err)
	}
	return dst
}

func rewriteFrameworkReplace(data []byte, framework string) []byte {
	const module = "git.golem15.com/golem15/summercms"
	lines := strings.Split(string(data), "\n")
	for i, line := range lines {
		trimmed := strings.TrimSpace(line)
		switch {
		case strings.HasPrefix(trimmed, "replace "+module+" =>"):
			indent := line[:len(line)-len(strings.TrimLeft(line, " \t"))]
			lines[i] = indent + "replace " + module + " => " + framework
		case strings.HasPrefix(trimmed, module+" =>"):
			indent := line[:len(line)-len(strings.TrimLeft(line, " \t"))]
			lines[i] = indent + module + " => " + framework
		}
	}
	return []byte(strings.Join(lines, "\n"))
}

func writeWatchApp(t *testing.T, dir string) {
	t.Helper()
	write(t, filepath.Join(dir, "summer.yaml"), "module: example.com/app\nbinary: hello\nplugins:\n  - id: a.b\n    module: example.com/app/plugins/demo\n")
	write(t, filepath.Join(dir, "plugin.go"), "package p\n")
	write(t, filepath.Join(dir, "main.go"), "package main\n")
	write(t, filepath.Join(dir, "plugins.gen.go"), "package main\n")
}

func write(t *testing.T, path, body string) {
	t.Helper()
	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
}

func waitUntil(t *testing.T, name string, ok func() bool) {
	t.Helper()
	deadline := time.Now().Add(3 * time.Second)
	for time.Now().Before(deadline) {
		if ok() {
			return
		}
		time.Sleep(15 * time.Millisecond)
	}
	t.Fatalf("timed out waiting for %s", name)
}

// fakeServe writes an executable that records its arguments in
// $DEV_ARGS_FILE and, on SIGTERM, writes "term" to $DEV_TERM_FILE and exits
// 0, like serve's graceful stop.
func fakeServe(t *testing.T, path string) (argsFile, termFile string) {
	t.Helper()
	dir := t.TempDir()
	argsFile, termFile = filepath.Join(dir, "args"), filepath.Join(dir, "term")
	t.Setenv("DEV_ARGS_FILE", argsFile)
	t.Setenv("DEV_TERM_FILE", termFile)
	script := "#!/bin/sh\n" +
		"printf '%s\\n' \"$*\" > \"$DEV_ARGS_FILE\"\n" +
		"trap 'echo term > \"$DEV_TERM_FILE\"; exit 0' TERM\n" +
		"while :; do sleep 0.05; done\n"
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(path, []byte(script), 0o755); err != nil {
		t.Fatal(err)
	}
	return argsFile, termFile
}

func readTrimmed(path string) string {
	b, _ := os.ReadFile(path)
	return strings.TrimSpace(string(b))
}

// TestStartBinServe: summer dev starts bin/<binary> with "serve" first and
// then the forwarded global options, through the real startBin.
func TestStartBinServe(t *testing.T) {
	bin := filepath.Join(t.TempDir(), "bin", "hello")
	argsFile, _ := fakeServe(t, bin)
	var out safeBuffer
	cmd, err := startBin(t.Context(), bin, []string{"serve", "-vv", "--env=staging"}, &out, &out)
	if err != nil {
		t.Fatal(err)
	}
	waitUntil(t, "args written", func() bool { return readTrimmed(argsFile) != "" })
	_ = cmd.Process.Signal(syscall.SIGTERM)
	_ = cmd.Wait()
	if got := readTrimmed(argsFile); got != "serve -vv --env=staging" {
		t.Fatalf("child args = %q", got)
	}

	// Through watch: the default Start runs serve with the globals summer
	// dev was given.
	dir := t.TempDir()
	writeWatchApp(t, dir)
	argsFile, _ = fakeServe(t, filepath.Join(dir, "bin", "hello"))
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()
	done := make(chan error, 1)
	opts := Options{Debounce: 40 * time.Millisecond, Build: func(context.Context, string, io.Writer) error { return nil }}
	go func() { done <- watch(ctx, dir, testOutput(&out), []string{"-q", "--no-ansi"}, opts) }()
	waitUntil(t, "child started", func() bool { return readTrimmed(argsFile) != "" })
	if got := readTrimmed(argsFile); got != "serve -q --no-ansi" {
		t.Fatalf("watch started the child with %q", got)
	}
	if !strings.Contains(out.String(), "running bin/hello serve -q --no-ansi") {
		t.Errorf("watch line lacks the child command:\n%s", out.String())
	}
	cancel()
	<-done
}

// TestDevReport: the dev report counts successful and failed rebuilds and
// restarts; a failed build keeps the running child.
func TestDevReport(t *testing.T) {
	r := devReport{rebuilds: 2, failed: 1, restarts: 1, started: time.Now().Add(-90 * time.Second)}
	d := r.details()
	if d[0].Value != "3 (1 failed)" || !d[0].Warn || d[1].Value != "1" || d[2].Value != "1m30s" {
		t.Fatalf("details = %+v", d)
	}
	if clean := (devReport{rebuilds: 1, started: time.Now()}).details(); clean[0].Value != "1 (0 failed)" || clean[0].Warn {
		t.Fatalf("clean details = %+v", clean)
	}

	dir := t.TempDir()
	writeWatchApp(t, dir)
	var out safeBuffer
	var builds, starts atomic.Int32
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()
	opts := Options{
		Debounce: 40 * time.Millisecond,
		Build: func(context.Context, string, io.Writer) error {
			if builds.Add(1) == 2 {
				return fmt.Errorf("syntax error")
			}
			return nil
		},
		Start: func(context.Context, string, []string, io.Writer, io.Writer) (*exec.Cmd, error) {
			starts.Add(1)
			cmd := exec.Command("sleep", "30")
			return cmd, cmd.Start()
		},
	}
	done := make(chan error, 1)
	go func() { done <- watch(ctx, dir, testOutput(&out), nil, opts) }()
	waitUntil(t, "initial start", func() bool { return starts.Load() == 1 })
	write(t, filepath.Join(dir, "plugin.go"), "package p\n// broken\n")
	waitUntil(t, "failed build", func() bool { return builds.Load() == 2 })
	waitUntil(t, "build failure line", func() bool { return strings.Contains(out.String(), "Build failed: syntax error") })
	write(t, filepath.Join(dir, "plugin.go"), "package p\n// fixed\n")
	waitUntil(t, "restart", func() bool { return starts.Load() == 2 })
	cancel()
	if err := <-done; err != nil {
		t.Fatalf("watch returned %v", err)
	}
	got := out.String()
	for _, want := range []string{"Dev report", "Rebuilds  3 (1 failed)", "Restarts  1", "Uptime"} {
		if !strings.Contains(got, want) {
			t.Errorf("dev report lacks %q:\n%s", want, got)
		}
	}
}

// TestDevGracefulNil: when summer dev is stopped it sends SIGTERM to the
// running serve, which stops gracefully, prints the dev report and returns
// nil (exit 0).
func TestDevGracefulNil(t *testing.T) {
	dir := t.TempDir()
	writeWatchApp(t, dir)
	argsFile, termFile := fakeServe(t, filepath.Join(dir, "bin", "hello"))
	var out safeBuffer
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()
	done := make(chan error, 1)
	opts := Options{Debounce: 40 * time.Millisecond, Build: func(context.Context, string, io.Writer) error { return nil }}
	go func() { done <- watch(ctx, dir, testOutput(&out), nil, opts) }()
	waitUntil(t, "child started", func() bool { return readTrimmed(argsFile) == "serve" })
	cancel()
	select {
	case err := <-done:
		if err != nil {
			t.Fatalf("watch returned %v after stop, want nil", err)
		}
	case <-time.After(5 * time.Second):
		t.Fatal("watch did not stop")
	}
	if readTrimmed(termFile) != "term" {
		t.Fatal("serve did not get SIGTERM")
	}
	if !strings.Contains(out.String(), "Dev report") || !strings.Contains(out.String(), "Restarts  0") {
		t.Fatalf("no dev report:\n%s", out.String())
	}
}