package handlers_test

import (
	"bytes"
	"compress/gzip"
	"context"
	"crypto/rand"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/delivery"
	"sneak.berlin/go/webhooker/internal/middleware"
)

// errClientGone is the write failure of a client that has gone away.
var errClientGone = errors.New("client gone")

// downloadPath is the archive download route of a target.
func downloadPath(webhookID, targetID string) string {
	return "/hook/" + webhookID + "/targets/" + targetID + "/download"
}

// renameTarget submits the edit form renaming a target to Renamed.
func renameTarget(
	env *sourceTestEnv, webhookID, targetID string,
) *httptest.ResponseRecorder {
	form := url.Values{}
	form.Set("name", "Renamed")

	return submitTargetEdit(env, webhookID, targetID, form)
}

// TestHandleTargetDownload proves a database target's archive
// downloads as a gzipped JSON attachment named for the webhook, the
// target and the time, here with no archive file yet, so with no
// rows; and that a target of another type has no download.
func TestHandleTargetDownload(t *testing.T) {
	t.Parallel()

	env := setupSourceTest(t)
	wh := seedWebhookWithRetention(t, env.db, 7)
	archive := seedTarget(t, env.db, wh.ID, database.TargetTypeDatabase)
	logTarget := seedTarget(t, env.db, wh.ID, database.TargetTypeLog)

	w := serveTarget(
		env, http.MethodGet, downloadPath(wh.ID, archive.ID), nil,
	)
	require.Equal(t, http.StatusOK, w.Code, w.Body.String())
	assert.Equal(t, "application/gzip", w.Header().Get("Content-Type"))
	assert.Regexp(t,
		`^attachment; filename="archive-seeded-t-database-`+
			`\d{8}T\d{6}Z\.json\.gz"$`,
		w.Header().Get("Content-Disposition"),
	)

	zr, err := gzip.NewReader(w.Body)
	require.NoError(t, err)

	var got map[string]json.RawMessage

	require.NoError(t, json.NewDecoder(zr).Decode(&got))
	assert.JSONEq(t,
		`{"id":"`+archive.ID+`","name":"t-database"}`,
		string(got["target"]),
	)
	assert.JSONEq(t, `[]`, string(got["archived_events"]))

	w = serveTarget(
		env, http.MethodGet, downloadPath(wh.ID, logTarget.ID), nil,
	)
	assert.Equal(t, http.StatusNotFound, w.Code)
}

// TestHandleTargetDownload_WaitsForRename proves a download reads the
// target's names and lists its archive under the lock a rename holds:
// started while an edit is renaming the archive, it waits, and is
// named for the target's new name.
func TestHandleTargetDownload_WaitsForRename(t *testing.T) {
	t.Parallel()

	env := setupSourceTest(t)
	wh := seedWebhookWithRetention(t, env.db, 7)
	archive := seedTarget(t, env.db, wh.ID, database.TargetTypeDatabase)

	renaming, release := env.archives.BlockNextRename()
	edited := make(chan *httptest.ResponseRecorder, 1)

	go func() {
		edited <- renameTarget(env, wh.ID, archive.ID)
	}()

	<-renaming

	downloaded := make(chan *httptest.ResponseRecorder, 1)

	go func() {
		downloaded <- serveTarget(
			env, http.MethodGet, downloadPath(wh.ID, archive.ID), nil,
		)
	}()

	select {
	case <-downloaded:
		release()
		t.Fatal("the download did not wait for the rename")
	case <-time.After(100 * time.Millisecond):
	}

	release()
	require.Equal(t, http.StatusSeeOther, (<-edited).Code)

	w := <-downloaded
	require.Equal(t, http.StatusOK, w.Code)
	assert.Contains(t,
		w.Header().Get("Content-Disposition"), "archive-seeded-renamed-",
	)
}

// stalledWriter is a response writer whose first write waits until
// resume is closed, closing writing when it starts to wait.
type stalledWriter struct {
	*httptest.ResponseRecorder

	once    sync.Once
	writing chan struct{}
	resume  chan struct{}
}

func (s *stalledWriter) Write(b []byte) (int, error) {
	s.once.Do(func() {
		close(s.writing)
		<-s.resume
	})

	return s.ResponseRecorder.Write(b)
}

// startStalledDownload starts a download of the target and returns once
// it is stalled at its first write, which comes before it opens any
// archive file. Closing the writer's resume lets it go on; the returned
// channel is closed when it has finished.
func startStalledDownload(
	t *testing.T, env *sourceTestEnv, webhookID, targetID string,
) (*stalledWriter, <-chan struct{}) {
	t.Helper()

	req := httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, downloadPath(webhookID, targetID), nil,
	)
	for _, c := range env.cookies {
		req.AddCookie(c)
	}

	sw := &stalledWriter{
		ResponseRecorder: httptest.NewRecorder(),
		writing:          make(chan struct{}),
		resume:           make(chan struct{}),
	}
	downloaded := make(chan struct{})

	go func() {
		targetRouter(env).ServeHTTP(sw, req)
		close(downloaded)
	}()

	<-sw.writing

	return sw, downloaded
}

// TestHandleTargetDownload_StreamsWithoutTheLock proves a download
// lets go of the rename lock once it has listed its archive: while the
// download is stalled writing, an edit can still rename the target.
func TestHandleTargetDownload_StreamsWithoutTheLock(t *testing.T) {
	t.Parallel()

	env := setupSourceTest(t)
	wh := seedWebhookWithRetention(t, env.db, 7)
	archive := seedTarget(t, env.db, wh.ID, database.TargetTypeDatabase)

	sw, downloaded := startStalledDownload(t, env, wh.ID, archive.ID)

	edited := make(chan *httptest.ResponseRecorder, 1)

	go func() {
		edited <- renameTarget(env, wh.ID, archive.ID)
	}()

	select {
	case w := <-edited:
		assert.Equal(t, http.StatusSeeOther, w.Code)
	case <-time.After(10 * time.Second):
		t.Error("the rename waited for the download")
	}

	close(sw.resume)
	<-downloaded
	assert.Equal(t, http.StatusOK, sw.Code)
}

// TestHandleTargetDownload_FindsFilesAfterRename proves a download
// finds each of the target's files again under the names stored when
// it reaches the file: the target is renamed while the download is
// stalled before it has opened any file, and the rows of both its files
// are in the download.
func TestHandleTargetDownload_FindsFilesAfterRename(t *testing.T) {
	t.Parallel()

	env := setupSourceTest(t)
	wh := seedWebhookWithRetention(t, env.db, 7)
	archive := seedTarget(t, env.db, wh.ID, database.TargetTypeDatabase)
	oldPath := delivery.ArchivePath(env.dbMgr, &wh, archive)

	month := func(path string) string {
		return strings.TrimSuffix(path, ".db") + "-2026-10.db"
	}

	seedArchive(t, oldPath, 1, 16)
	seedArchive(t, month(oldPath), 1, 16)

	sw, downloaded := startStalledDownload(t, env, wh.ID, archive.ID)

	require.Equal(t,
		http.StatusSeeOther, renameTarget(env, wh.ID, archive.ID).Code,
	)

	// The test's archives record a rename without moving any file, so
	// the files are moved here, as the delivery engine moves them.
	var renamed database.Target

	require.NoError(t, env.db.DB().First(&renamed, "id = ?", archive.ID).Error)

	newPath := delivery.ArchivePath(env.dbMgr, &wh, &renamed)

	require.NoError(t, os.Rename(oldPath, newPath))
	require.NoError(t, os.Rename(month(oldPath), month(newPath)))

	close(sw.resume)
	<-downloaded
	require.Equal(t, http.StatusOK, sw.Code)

	zr, err := gzip.NewReader(sw.Body)
	require.NoError(t, err)

	var (
		got    map[string]json.RawMessage
		events []map[string]any
	)

	require.NoError(t, json.NewDecoder(zr).Decode(&got))
	require.NoError(t, json.Unmarshal(got["archived_events"], &events))
	require.Len(t, events, 2)
	assert.NotContains(t, events[0], "period")
	assert.Equal(t, "2026-10", events[1]["period"])
}

// seedArchive writes rows to the archive file at path, each with a
// body of bodySize random bytes, which do not compress. Its table has
// only the columns the test fills; an export writes the others empty.
func seedArchive(t *testing.T, path string, rows, bodySize int) {
	t.Helper()

	db, err := database.OpenSQLite(path, database.SQLiteModeCreate)
	require.NoError(t, err)

	defer func() { require.NoError(t, db.Close()) }()

	_, err = db.ExecContext(t.Context(),
		"CREATE TABLE archived_events (id INTEGER PRIMARY KEY, body TEXT)",
	)
	require.NoError(t, err)

	body := make([]byte, bodySize)

	for range rows {
		_, _ = rand.Read(body)

		_, err = db.ExecContext(t.Context(),
			"INSERT INTO archived_events (body) VALUES (?)", string(body),
		)
		require.NoError(t, err)
	}
}

// limitedServer serves the target routes as the server does, behind the
// access log, whose lines it returns, and the request limit, here
// limit, which is also its write timeout. Each connection's send buffer
// is a few KiB, so a larger response is still being written while its
// client is not reading.
func limitedServer(
	t *testing.T, env *sourceTestEnv, limit time.Duration,
) (*httptest.Server, *bytes.Buffer) {
	t.Helper()

	const sendBuffer = 4 << 10

	logBuf := new(bytes.Buffer)
	mw := middleware.NewForTest(
		slog.New(slog.NewJSONHandler(logBuf, nil)),
		&config.Config{Environment: config.EnvironmentDev},
		nil,
	)

	srv := httptest.NewUnstartedServer(
		mw.Logging()(mw.Timeout(limit)(targetRouter(env))),
	)
	srv.Config.WriteTimeout = limit
	srv.Config.ConnContext = func(
		ctx context.Context, c net.Conn,
	) context.Context {
		tcp, ok := c.(*net.TCPConn)
		if assert.True(t, ok) {
			assert.NoError(t, tcp.SetWriteBuffer(sendBuffer))
		}

		return ctx
	}
	srv.Start()
	t.Cleanup(srv.Close)

	return srv, logBuf
}

// TestHandleTargetDownload_OutlastsTheRequestLimit proves a download
// runs for as long as the client keeps reading, and is logged as the
// 200 it was. Behind a request limit and a server write timeout of a
// tenth of a second, the client stops reading once the response has
// started, waits three times as long, and still gets the whole file.
// The archive is larger than the connection holds, so the download is
// still being written while the client waits.
func TestHandleTargetDownload_OutlastsTheRequestLimit(t *testing.T) {
	t.Parallel()

	const (
		limit    = 100 * time.Millisecond
		rows     = 8
		bodySize = 64 << 10
	)

	env := setupSourceTest(t)
	wh := seedWebhookWithRetention(t, env.db, 7)
	archive := seedTarget(t, env.db, wh.ID, database.TargetTypeDatabase)
	seedArchive(
		t, delivery.ArchivePath(env.dbMgr, &wh, archive), rows, bodySize,
	)

	srv, accessLog := limitedServer(t, env, limit)

	req, err := http.NewRequestWithContext(
		t.Context(), http.MethodGet,
		srv.URL+downloadPath(wh.ID, archive.ID), nil,
	)
	require.NoError(t, err)

	for _, c := range env.cookies {
		req.AddCookie(c)
	}

	resp, err := srv.Client().Do(req)
	require.NoError(t, err)

	defer func() { _ = resp.Body.Close() }()

	require.Equal(t, http.StatusOK, resp.StatusCode)

	time.Sleep(3 * limit)

	zr, err := gzip.NewReader(resp.Body)
	require.NoError(t, err)

	var (
		got    map[string]json.RawMessage
		events []json.RawMessage
	)

	require.NoError(t, json.NewDecoder(zr).Decode(&got))
	require.NoError(t, json.Unmarshal(got["archived_events"], &events))
	assert.Len(t, events, rows)

	// Reading to the end makes the gzip reader check that the file was
	// finished.
	_, err = io.ReadAll(zr)
	require.NoError(t, err)

	// Close waits for the handler, so the access log line is written.
	srv.Close()

	var access map[string]any

	require.NoError(t, json.Unmarshal(accessLog.Bytes(), &access))
	assert.EqualValues(t, http.StatusOK, access["status"])
	assert.GreaterOrEqual(t,
		access["latency_ms"], float64(limit.Milliseconds()),
		"the download must outlast the request limit",
	)
}

// brokenWriter is a response writer whose writes fail once the
// response has started, as they do when the client goes away.
type brokenWriter struct {
	*httptest.ResponseRecorder
}

func (b brokenWriter) Write(p []byte) (int, error) {
	if b.Body.Len() > 0 {
		return 0, errClientGone
	}

	return b.ResponseRecorder.Write(p)
}

// TestHandleTargetDownload_AbortsWhenItFails proves a download that
// fails after its response has started aborts the connection, so the
// client sees a failed download rather than a file that looks
// complete and does not decompress.
func TestHandleTargetDownload_AbortsWhenItFails(t *testing.T) {
	t.Parallel()

	env := setupSourceTest(t)
	wh := seedWebhookWithRetention(t, env.db, 7)
	archive := seedTarget(t, env.db, wh.ID, database.TargetTypeDatabase)

	req := httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, downloadPath(wh.ID, archive.ID), nil,
	)
	for _, c := range env.cookies {
		req.AddCookie(c)
	}

	w := brokenWriter{ResponseRecorder: httptest.NewRecorder()}

	assert.PanicsWithValue(t, http.ErrAbortHandler, func() {
		targetRouter(env).ServeHTTP(w, req)
	})
	assert.Equal(t, http.StatusOK, w.Code)
}