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

package gemini

import (
	"bufio"
	"context"
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"math/big"
	"net"
	"net/url"
	"os"
	"strconv"
	"strings"
	"testing"
	"time"

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

type stringWriter struct{ sb *strings.Builder }

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

func testTLSConfig() *tls.Config {
	key, _ := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	tmpl := &x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject:      pkix.Name{CommonName: "localhost"},
		NotBefore:    time.Now(),
		NotAfter:     time.Now().Add(time.Hour),
		IPAddresses:  []net.IP{net.ParseIP("127.0.0.1")},
	}
	certDER, _ := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &key.PublicKey, key)
	return &tls.Config{
		Certificates: []tls.Certificate{{
			Certificate: [][]byte{certDER},
			PrivateKey:  key,
		}},
	}
}

func TestGeminiSuccess(t *testing.T) {
	cfg := testTLSConfig()
	listener, err := tls.Listen("tcp", "127.0.0.1:0", cfg)
	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("20 text/gemini\r\n# Hello\n\nContent.\n"))
	}()

	proto := NewProtocol()
	proto.TLSInsecure = true
	u, _ := url.Parse("gemini://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") {
		t.Errorf("got %q", buf.String())
	}
}

func TestGeminiTemporaryFailure(t *testing.T) {
	cfg := testTLSConfig()
	listener, _ := tls.Listen("tcp", "127.0.0.1:0", cfg)
	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("40 overloaded\r\n"))
	}()

	proto := NewProtocol()
	proto.TLSInsecure = true
	u, _ := url.Parse("gemini://127.0.0.1:" + strconv.Itoa(port) + "/")
	_, err := proto.Download(context.Background(), &core.DownloadRequest{URL: u})
	if err == nil {
		t.Error("expected temporary failure error")
	}
}

func TestGeminiPermanentFailure(t *testing.T) {
	cfg := testTLSConfig()
	listener, _ := tls.Listen("tcp", "127.0.0.1:0", cfg)
	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("51 not found\r\n"))
	}()

	proto := NewProtocol()
	proto.TLSInsecure = true
	u, _ := url.Parse("gemini://127.0.0.1:" + strconv.Itoa(port) + "/")
	_, err := proto.Download(context.Background(), &core.DownloadRequest{URL: u})
	if err == nil {
		t.Error("expected permanent failure error")
	}
}

// TestGeminiPinnedCertMismatch exercises the certificate-pinning path.
// The server presents a self-signed cert whose hash does NOT match the
// pinned value, so the download must fail with a pinning error.
func TestGeminiPinnedCertMismatch(t *testing.T) {
	cfg := testTLSConfig()
	listener, err := tls.Listen("tcp", "127.0.0.1:0", cfg)
	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("20 text/gemini\r\nhello\n"))
	}()

	proto := NewProtocol()
	proto.TLSInsecure = true // accept self-signed, then let pinning reject
	u, _ := url.Parse("gemini://127.0.0.1:" + strconv.Itoa(port) + "/")
	_, err = proto.Download(context.Background(), &core.DownloadRequest{
		URL:            u,
		PinnedCertHash: "0000000000000000000000000000000000000000000000000000000000000000",
	})
	if err == nil {
		t.Fatal("expected pinning failure")
	}
	if !strings.Contains(err.Error(), "pinning failed") {
		t.Errorf("expected pinning error, got: %v", err)
	}
}

// TestGeminiResumeSaveMetadata verifies that partial download progress is
// persisted to a .goget.meta sidecar when the context is cancelled.
func TestGeminiResumeSaveMetadata(t *testing.T) {
	cfg := testTLSConfig()
	listener, err := tls.Listen("tcp", "127.0.0.1:0", cfg)
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	// Send data in small pieces with delays so the download is still in
	// progress when the context is cancelled.
	body := make([]byte, 2000)
	for i := range body {
		body[i] = 'A'
	}
	go func() {
		conn, _ := listener.Accept()
		if conn == nil {
			return
		}
		defer conn.Close()
		r := bufio.NewReader(conn)
		r.ReadString('\n')
		conn.Write([]byte("20 application/octet-stream\r\n"))
		// Send 500 bytes per chunk with 100ms delays.
		for off := 0; off < len(body); off += 500 {
			end := off + 500
			if end > len(body) {
				end = len(body)
			}
			conn.Write(body[off:end])
			time.Sleep(100 * time.Millisecond)
		}
	}()

	tmp := t.TempDir()
	outPath := tmp + "/partial.bin"

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

	ctx, cancel := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		_, err := proto.Download(ctx, &core.DownloadRequest{
			URL:    u,
			Output: outPath,
		})
		errCh <- err
	}()

	// Cancel mid-download — the slow server keeps the connection open
	// long enough for the cancellation to fire between reads.
	time.Sleep(150 * time.Millisecond)
	cancel()

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

	// Verify resume metadata was saved.
	metaPath := outPath + output.ResumeMetaFileSuffix
	if _, err := os.Stat(metaPath); os.IsNotExist(err) {
		t.Fatal("expected .goget.meta sidecar to exist")
	}

	meta, err := output.LoadResumeMetadata(outPath)
	if err != nil {
		t.Fatalf("LoadResumeMetadata: %v", err)
	}
	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())
	}
}

// TestGeminiResumeDownload verifies end-to-end resume: a first download is
// interrupted, and the second download picks up from the saved offset.
func TestGeminiResumeDownload(t *testing.T) {
	cfg := testTLSConfig()
	listener, err := tls.Listen("tcp", "127.0.0.1:0", cfg)
	if err != nil {
		t.Fatal(err)
	}
	defer listener.Close()
	port := listener.Addr().(*net.TCPAddr).Port

	fullBody := make([]byte, 1000)
	for i := range fullBody {
		fullBody[i] = byte('A' + i%26)
	}
	cancelReady := make(chan struct{}) // client signals it has cancelled
	connReady := make(chan struct{})   // server signals connection is done
	go func() {
		for i := 0; i < 2; i++ {
			conn, lerr := listener.Accept()
			if lerr != nil {
				return
			}
			r := bufio.NewReader(conn)
			r.ReadString('\n')
			conn.Write([]byte("20 application/octet-stream\r\n"))
			if i == 0 {
				// First connection: send 500 bytes, then wait
				// for the client to cancel before closing.
				conn.Write(fullBody[:500])
				<-cancelReady
				conn.Close()
				connReady <- struct{}{}
			} else {
				// Second connection: send the full body.
				conn.Write(fullBody)
				conn.Close()
			}
		}
	}()

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

	proto := NewProtocol()
	proto.TLSInsecure = true
	u, _ := url.Parse("gemini://127.0.0.1:" + strconv.Itoa(port) + "/data")

	// First attempt: the server sends 500 bytes and blocks. We cancel
	// the context, then the server closes the connection.
	ctx1, cancel1 := context.WithCancel(context.Background())
	errCh := make(chan error, 1)
	go func() {
		_, dlErr := proto.Download(ctx1, &core.DownloadRequest{
			URL:    u,
			Output: outPath,
		})
		errCh <- dlErr
	}()
	time.Sleep(100 * time.Millisecond)
	cancel1()
	cancelReady <- struct{}{} // let server close connection
	<-connReady
	dlErr := <-errCh
	if dlErr == nil {
		t.Fatal("expected error from cancelled context")
	}

	// Verify partial file and metadata exist.
	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.
	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 now contain the full body.
	data, readErr := os.ReadFile(outPath)
	if readErr != nil {
		t.Fatalf("read output: %v", readErr)
	}
	if string(data) != string(fullBody) {
		t.Errorf("file content length = %d, want %d", len(data), len(fullBody))
	}

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

// TestSaveGeminiResumeMetadata verifies the helper function directly.
func TestSaveGeminiResumeMetadata(t *testing.T) {
	tmp := t.TempDir()
	out := tmp + "/file.bin"

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

	saveGeminiResume(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 != "gemini://example.com/file.bin" {
		t.Errorf("URL = %q, want %q", meta.URL, "gemini://example.com/file.bin")
	}
	// Gemini doesn't expose Content-Length, so Total should be 0.
	if meta.Total != 0 {
		t.Errorf("Total = %d, want 0", meta.Total)
	}
}

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

	t.Run("stdout", func(t *testing.T) {
		saveGeminiResume(&core.DownloadRequest{URL: u, Output: "-"}, 100)
		// Should not panic or create any file.
	})

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

	t.Run("zero bytes", func(t *testing.T) {
		tmp := t.TempDir()
		saveGeminiResume(&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) {
		saveGeminiResume(nil, 100)
		// Should not panic.
	})
}