//go:build linux || freebsd
// +build linux freebsd

package gopher

import (
	"bufio"
	"context"
	"fmt"
	"net"
	"net/url"
	"os"
	"runtime"
	"strconv"
	"strings"
	"testing"
	"time"

	"codeberg.org/petrbalvin/goget/internal/core"
	"codeberg.org/petrbalvin/goget/internal/output"
)

func TestFormatGopherMenu(t *testing.T) {
	tests := []struct {
		line     string
		expected string
	}{
		{"0About\t/about\tgopher.floodgap.com\t70\r\n", "📄 About  [/about]"},
		{"1Fun\t/fun\tgopher.floodgap.com\t70\r\n", "📁 Fun  [/fun]"},
		{"iWelcome to Gopher\t(null)\t(null)\t0\r\n", "ℹ️ Welcome to Gopher"},
		{"hNews\t/news\tgopher.floodgap.com\t70\r\n", "🌐 News  [/news]"},
	}

	for _, tc := range tests {
		result := formatGopherMenu(tc.line)
		if result != tc.expected {
			t.Errorf("formatGopherMenu(%q) = %q, want %q", tc.line, result, tc.expected)
		}
	}
}

func TestStripGopherMeta(t *testing.T) {
	result := stripGopherMeta("0About\t/about\thost\t70")
	if result != "About" {
		t.Errorf("got %q, want %q", result, "About")
	}
}

func TestGopherIcon(t *testing.T) {
	if i := gopherIcon('0'); i != "📄" {
		t.Errorf("got %q", i)
	}
	if i := gopherIcon('1'); i != "📁" {
		t.Errorf("got %q", i)
	}
	if i := gopherIcon('9'); i != "💾" {
		t.Errorf("got %q", i)
	}
	if i := gopherIcon('h'); i != "🌐" {
		t.Errorf("got %q", i)
	}
	if i := gopherIcon('7'); i != "🔍" {
		t.Errorf("got %q", i)
	}
}

func TestIsTextGopherType(t *testing.T) {
	if !isTextGopherType('0') {
		t.Error("0 should be text")
	}
	if isTextGopherType('9') {
		t.Error("9 should not be text")
	}
}

type stringWriter struct{ sb *strings.Builder }

func (w *stringWriter) Write(p []byte) (int, error) { return w.sb.Write(p) }

func TestGopherDownloadMock(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()

	port := listener.Addr().(*net.TCPAddr).Port

	go func() {
		conn, _ := listener.Accept()
		if conn == nil {
			return
		}
		defer conn.Close()
		reader := bufio.NewReader(conn)
		reader.ReadString('\n') // selector
		conn.Write([]byte("0Hello from gopher\t(null)\t(null)\t0\r\n"))
		conn.Write([]byte(".\r\n"))
	}()

	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/")

	var buf strings.Builder
	_, err = proto.Download(context.Background(), &core.DownloadRequest{
		URL:    u,
		Writer: &stringWriter{&buf},
	})
	if err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(buf.String(), "Hello from gopher") {
		t.Errorf("output missing text: %q", buf.String())
	}
}

// TestGopherResumeSaveMetadata verifies that interrupting a Gopher text
// download persists a .goget.meta sidecar describing the partial state.
func TestGopherResumeSaveMetadata(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	go func() {
		conn, _ := listener.Accept()
		if conn == nil {
			return
		}
		defer conn.Close()
		reader := bufio.NewReader(conn)
		reader.ReadString('\n')
		// Send the first display line, sleep so the client has a chance
		// to land in the read loop and receive the cancellation, then
		// send the second line and the terminator.
		conn.Write([]byte("hFirst\t/first\thost\t70\r\n"))
		time.Sleep(150 * time.Millisecond)
		conn.Write([]byte("hSecond\t/second\thost\t70\r\n"))
		conn.Write([]byte(".\r\n"))
	}()

	tmp := t.TempDir()
	outPath := tmp + "/page.html"

	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/page")

	// progress is signalled every time the download loop calls
	// req.ProgressCallback — which happens *after* a successful
	// writer.Write. Reading from it is therefore a deterministic
	// barrier waiting for the first byte to land on disk.
	progress := make(chan int64, 1)

	ctx, cancel := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		_, dlErr := proto.Download(ctx, &core.DownloadRequest{
			URL:    u,
			Output: outPath,
			ProgressCallback: func(current, total int64, speed float64) {
				select {
				case progress <- current:
				default:
				}
			},
		})
		errCh <- dlErr
	}()

	// Wait until the first byte has been written to disk, then cancel.
	// No fixed sleep — this is robust against slow CI schedulers.
	<-progress
	cancel()

	dlErr := <-errCh
	if dlErr == nil {
		t.Fatal("expected error from cancelled context")
	}

	metaPath := outPath + output.ResumeMetaFileSuffix
	if _, statErr := os.Stat(metaPath); statErr != nil {
		t.Fatalf("expected .goget.meta sidecar to exist: %v", statErr)
	}

	meta, metaErr := output.LoadResumeMetadata(outPath)
	if metaErr != nil {
		t.Fatalf("LoadResumeMetadata: %v", metaErr)
	}
	if meta == nil {
		t.Fatal("expected resume metadata, got nil")
	}
	if meta.Downloaded <= 0 {
		t.Errorf("Downloaded = %d, want > 0", meta.Downloaded)
	}
	if meta.URL != u.String() {
		t.Errorf("URL = %q, want %q", meta.URL, u.String())
	}
	// Gopher does not expose Content-Length, so Total stays 0.
	if meta.Total != 0 {
		t.Errorf("Total = %d, want 0", meta.Total)
	}
	// Sanity-check: the saved Downloaded should match what's on disk.
	info, statErr := os.Stat(outPath)
	if statErr != nil {
		t.Fatalf("partial file missing: %v", statErr)
	}
	if info.Size() != meta.Downloaded {
		t.Errorf("file size = %d, metadata.Downloaded = %d (must match)",
			info.Size(), meta.Downloaded)
	}
}

// TestGopherResumeDownload verifies end-to-end resume: an interrupted
// download completes on the second attempt with --resume=true, and the
// metadata sidecar is removed after the successful completion.
func TestGopherResumeDownload(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	cancelReady := make(chan struct{})
	connReady := make(chan struct{})
	go func() {
		for i := 0; i < 2; i++ {
			conn, lerr := listener.Accept()
			if lerr != nil {
				return
			}
			r := bufio.NewReader(conn)
			r.ReadString('\n')
			if i == 0 {
				// First attempt: send the first line, then wait
				// for the client to cancel before closing.
				conn.Write([]byte("0Line one\t/foo\thost\t70\r\n"))
				<-cancelReady
				conn.Close()
				connReady <- struct{}{}
			} else {
				// Second attempt: send the full body.
				conn.Write([]byte("0Line one\t/foo\thost\t70\r\n"))
				conn.Write([]byte("0Line two\t/bar\thost\t70\r\n"))
				conn.Write([]byte(".\r\n"))
				conn.Close()
			}
		}
	}()

	tmp := t.TempDir()
	outPath := tmp + "/resume.txt"

	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/foo")

	// First attempt: send only the first line, then cancel.
	// progress signals after the first writer.Write, so waiting on
	// it replaces the previous fixed sleep with a deterministic barrier.
	progress := make(chan int64, 1)
	ctx1, cancel1 := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		_, dlErr := proto.Download(ctx1, &core.DownloadRequest{
			URL:    u,
			Output: outPath,
			ProgressCallback: func(current, total int64, speed float64) {
				select {
				case progress <- current:
				default:
				}
			},
		})
		errCh <- dlErr
	}()
	<-progress
	cancel1()
	cancelReady <- struct{}{}
	<-connReady
	dlErr := <-errCh
	if dlErr == nil {
		t.Fatal("expected error from cancelled context")
	}

	// Sanity-check: partial file + metadata sidecar present.
	info, statErr := os.Stat(outPath)
	if statErr != nil {
		t.Fatalf("partial file missing: %v", statErr)
	}
	if info.Size() == 0 {
		t.Fatal("partial file is empty")
	}
	meta, metaErr := output.LoadResumeMetadata(outPath)
	if metaErr != nil || meta == nil {
		t.Fatalf("expected resume metadata: err=%v meta=%v", metaErr, meta)
	}

	// Second attempt: resume should pick up where we left off.
	result, resErr := proto.Download(context.Background(), &core.DownloadRequest{
		URL:    u,
		Output: outPath,
		Resume: true,
	})
	if resErr != nil {
		t.Fatalf("resume download failed: %v", resErr)
	}
	if !result.Resumed {
		t.Error("expected Resumed=true")
	}

	// The file should contain the full body, with the resume logic
	// skipping already-written bytes via the post-transform offset.
	data, readErr := os.ReadFile(outPath)
	if readErr != nil {
		t.Fatalf("read output: %v", readErr)
	}
	want := "Line one\nLine two\n"
	if string(data) != want {
		t.Errorf("file content = %q, want %q", string(data), want)
	}

	// Metadata sidecar should be deleted after a successful completion.
	if output.FileExists(outPath + output.ResumeMetaFileSuffix) {
		t.Error("expected .goget.meta to be deleted after successful resume")
	}
}

// TestSaveGopherResumeMetadata exercises the helper directly.
func TestSaveGopherResumeMetadata(t *testing.T) {
	tmp := t.TempDir()
	out := tmp + "/file.txt"

	u, err := url.Parse("gopher://example.com/foo.txt")
	if err != nil {
		t.Fatalf("parse URL: %v", err)
	}
	req := &core.DownloadRequest{
		URL:    u,
		Output: out,
	}

	saveGopherResume(req, 4096)

	meta, err := output.LoadResumeMetadata(out)
	if err != nil {
		t.Fatalf("LoadResumeMetadata: %v", err)
	}
	if meta == nil {
		t.Fatal("expected resume metadata, got nil")
	}
	if meta.Downloaded != 4096 {
		t.Errorf("Downloaded = %d, want 4096", meta.Downloaded)
	}
	if meta.URL != "gopher://example.com/foo.txt" {
		t.Errorf("URL = %q, want %q", meta.URL, "gopher://example.com/foo.txt")
	}
	if meta.Total != 0 {
		t.Errorf("Total = %d, want 0", meta.Total)
	}
}

// TestSaveGopherResumeNoop verifies that the helper is a no-op for
// stdout writes, empty output paths, zero-byte transfers, and nil
// requests.
func TestSaveGopherResumeNoop(t *testing.T) {
	u, _ := url.Parse("gopher://example.com/")

	t.Run("stdout", func(t *testing.T) {
		saveGopherResume(&core.DownloadRequest{URL: u, Output: "-"}, 100)
	})

	t.Run("empty output", func(t *testing.T) {
		saveGopherResume(&core.DownloadRequest{URL: u, Output: ""}, 100)
	})

	t.Run("zero bytes", func(t *testing.T) {
		tmp := t.TempDir()
		saveGopherResume(&core.DownloadRequest{URL: u, Output: tmp + "/f"}, 0)
		if output.FileExists(tmp + "/f" + output.ResumeMetaFileSuffix) {
			t.Error("metadata created for zero-byte transfer")
		}
	})

	t.Run("nil request", func(t *testing.T) {
		saveGopherResume(nil, 100)
	})
}

// TestGopherResumeStaleMetadata exercises the path where the .goget.meta
// sidecar exists but the partial file doesn't (or has been truncated),
// forcing the resume code to clean up and start fresh.
func TestGopherResumeStaleMetadata(t *testing.T) {
	tmp := t.TempDir()
	outPath := tmp + "/stale.txt"

	// Pre-create an orphan .goget.meta for a URL we will not use.
	orphanMeta := output.NewResumeMetadata("gopher://other.example/foo", "", "", 1234, 0)
	if err := orphanMeta.Save(outPath); err != nil {
		t.Fatalf("seed meta: %v", err)
	}
	// Do not pre-create the partial file; CanResume requires file size
	// to match metadata Downloaded.

	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	go func() {
		conn, _ := listener.Accept()
		if conn == nil {
			return
		}
		defer conn.Close()
		r := bufio.NewReader(conn)
		r.ReadString('\n')
		conn.Write([]byte("0Fresh\t/fresh\thost\t70\r\n.\r\n"))
	}()

	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/fresh")

	res, err := proto.Download(context.Background(), &core.DownloadRequest{
		URL:    u,
		Output: outPath,
		Resume: true,
	})
	if err != nil {
		t.Fatalf("download: %v", err)
	}
	if res.Resumed {
		t.Error("expected Resumed=false after stale-metadata cleanup")
	}
	data, _ := os.ReadFile(outPath)
	if string(data) != "Fresh\n" {
		t.Errorf("content = %q, want %q", string(data), "Fresh\n")
	}
	// The orphan sidecar from a different URL must be removed once the
	// successful fresh download completes — otherwise stale metadata
	// could be picked up by a future --resume run.
	if output.FileExists(outPath + output.ResumeMetaFileSuffix) {
		t.Error("expected orphan .goget.meta to be deleted after fresh download")
	}
}

// TestGopherResumeIgnoredWhenWriterSet verifies that --resume is silently
// disabled when the caller also supplies a Writer: the resume metadata
// sidecar would otherwise lie about bytes written to Output, since the
// real data ends up in the Writer.
func TestGopherResumeIgnoredWhenWriterSet(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	go func() {
		conn, _ := listener.Accept()
		if conn == nil {
			return
		}
		defer conn.Close()
		r := bufio.NewReader(conn)
		r.ReadString('\n')
		conn.Write([]byte("0Line one\t/foo\thost\t70\r\n.\r\n"))
	}()

	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/foo")
	outPath := t.TempDir() + "/ignored-output.txt"

	var buf strings.Builder
	res, dlErr := proto.Download(context.Background(), &core.DownloadRequest{
		URL:    u,
		Output: outPath,
		Writer: &stringWriter{&buf},
		Resume: true,
	})
	if dlErr != nil {
		t.Fatalf("download: %v", dlErr)
	}
	if res.Resumed {
		t.Error("expected Resumed=false when Writer is set (resume must be ignored)")
	}
	if !strings.Contains(buf.String(), "Line one") {
		t.Errorf("writer should receive the body, got %q", buf.String())
	}
	// Output is supplied but a Writer takes precedence; the file must
	// not be created or touched by resume machinery.
	if _, statErr := os.Stat(outPath); statErr == nil {
		t.Error("Output file should not be created when Writer is set")
	}
}

// TestGopherResumeInformation verifies that resume machinery works for the
// informational (type i) response path, which is also routed through
// downloadText. Informational lines are passed through verbatim (no
// metadata strip), so the resume offset matches the raw line length
// including trailing CR/LF.
func TestGopherResumeInformation(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	cancelReady := make(chan struct{})
	connReady := make(chan struct{})
	go func() {
		for i := 0; i < 2; i++ {
			conn, lerr := listener.Accept()
			if lerr != nil {
				return
			}
			r := bufio.NewReader(conn)
			r.ReadString('\n')
			if i == 0 {
				// First half: send two info lines, then wait
				// for the client to cancel before closing.
				conn.Write([]byte("iFirst line.\r\n"))
				conn.Write([]byte("iSecond line.\r\n"))
				<-cancelReady
				conn.Close()
				connReady <- struct{}{}
			} else {
				// Second half: full body.
				conn.Write([]byte("iFirst line.\r\n"))
				conn.Write([]byte("iSecond line.\r\n"))
				conn.Write([]byte(".\r\n"))
				conn.Close()
			}
		}
	}()

	tmp := t.TempDir()
	outPath := tmp + "/info.txt"

	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/info")

	progress := make(chan int64, 1)
	ctx1, cancel1 := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		_, dlErr := proto.Download(ctx1, &core.DownloadRequest{
			URL:    u,
			Output: outPath,
			ProgressCallback: func(current, total int64, speed float64) {
				select {
				case progress <- current:
				default:
				}
			},
		})
		errCh <- dlErr
	}()
	<-progress
	cancel1()
	cancelReady <- struct{}{}
	<-connReady
	if dlErr := <-errCh; dlErr == nil {
		t.Fatal("expected error from cancelled context")
	}

	// Resume should append the missing bytes. For informational lines
	// we do not strip metadata, so the output preserves the server CR/LF.
	result, resErr := proto.Download(context.Background(), &core.DownloadRequest{
		URL:    u,
		Output: outPath,
		Resume: true,
	})
	if resErr != nil {
		t.Fatalf("resume download failed: %v", resErr)
	}
	if !result.Resumed {
		t.Error("expected Resumed=true")
	}
	if result.ContentType != "text/plain" {
		t.Errorf("ContentType = %q, want text/plain", result.ContentType)
	}

	data, _ := os.ReadFile(outPath)
	// Informational lines are passed through verbatim: the 'i' item-type
	// prefix and CR/LF framing from the server survive into the output.
	want := "iFirst line.\r\niSecond line.\r\n"
	if string(data) != want {
		t.Errorf("content = %q, want %q", string(data), want)
	}
	if output.FileExists(outPath + output.ResumeMetaFileSuffix) {
		t.Error("expected .goget.meta to be deleted after successful resume")
	}
}

// TestGopherCancelGoroutineExits verifies that the ctx-cancellation
// goroutine spawned by Download does not outlive Download itself.
// The goroutine used to wait forever on <-ctx.Done() when the parent
// context was never cancelled; the done-channel bound added with M3
// must let every iteration return to the runtime goroutine pool.
func TestGopherCancelGoroutineExits(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	go func() {
		// Drain connections so the listener does not backpressure
		// the test loop. We do not read or write — a quick accept
		// and close is enough for Download to complete.
		for {
			conn, lerr := listener.Accept()
			if lerr != nil {
				return
			}
			go func(c net.Conn) {
				// Reply with the response header so the client
				// reaches downloadText and spawns its goroutine.
				defer c.Close()
				fmt.Fprintf(c, "0hi\t/x\th\t70\r\n.\r\n")
				// Block until the peer closes — this lets the
				// client-side goroutine sit on ReadString until
				// it's raced by done, exercising the bound.
				buf := make([]byte, 1)
				c.Read(buf)
			}(conn)
		}
	}()

	// Warm up: a single download is enough to settle the runtime
	// goroutine pool (timer, GC, poll, etc.) before we measure.
	proto := NewProtocol()
	u, _ := url.Parse("gopher://127.0.0.1:" + strconv.Itoa(port) + "/x")
	req := core.DownloadRequest{URL: u, Writer: &stringWriter{&strings.Builder{}}}
	if _, dlErr := proto.Download(context.Background(), &req); dlErr != nil {
		t.Fatalf("warmup: %v", dlErr)
	}

	// Settle baseline after warmup.
	runtime.GC()
	time.Sleep(50 * time.Millisecond)
	runtime.GC()
	baseline := runtime.NumGoroutine()

	const iterations = 50
	for i := 0; i < iterations; i++ {
		if _, dlErr := proto.Download(context.Background(), &req); dlErr != nil {
			t.Fatalf("download %d: %v", i, dlErr)
		}
	}

	// After every successful Download returns, its cancellation
	// goroutine must have exited. Allow a brief settle window for
	// the runtime to reclaim them.
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		runtime.GC()
		time.Sleep(50 * time.Millisecond)
		// One tolerance for any incidental stdlib goroutine that
		// the Go runtime occasionally spins up between calls.
		if runtime.NumGoroutine() <= baseline+1 {
			return
		}
	}
	t.Fatalf("goroutine leak: baseline=%d, after %d downloads = %d",
		baseline, iterations, runtime.NumGoroutine())
}