package main

import (
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

func TestLogReopenLoadsTheSameMessages(t *testing.T) {
	root := t.TempDir()
	clock := newTestClock()
	log, err := openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

	var written []Message
	for _, kind := range []string{"user", "reply", "tool", "echo", "work", "note"} {
		message, err := log.Append(kind, kind+" text ✓")
		require.NoError(t, err)

		written = append(written, message)
	}

	require.Equal(t, 5, written[5].ID)
	require.Equal(t, len("note text ✓"), written[5].Size)
	require.NoError(t, log.Close())

	log, err = openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

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

	require.Equal(t, len(written), log.Len())
	for _, message := range written {
		read, err := log.Message(message.ID)
		require.NoError(t, err)
		require.Equal(t, message, read)
	}

	message, err := log.Append("user", "after the reopen")
	require.NoError(t, err)
	require.Equal(t, 6, message.ID)
}

func TestLogBuildsAMissingIndexAgain(t *testing.T) {
	root := t.TempDir()
	clock := newTestClock()
	log, err := openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

	for _, text := range []string{"a", "b", "c"} {
		_, err = log.Append("user", text)
		require.NoError(t, err)

		clock.now = clock.now.Add(24 * time.Hour)
	}

	require.NoError(t, log.Close())

	// A missing index, and an index that a crash cut in a record.
	for _, cut := range []func(string) error{os.Remove, truncateToOneAndAHalf} {
		require.NoError(t, cut(filepath.Join(root, "index", "main.idx")))

		log, err = openLog(t.Context(), root, clock.Now)
		require.NoError(t, err)
		require.Equal(t, 3, log.Len())

		message, err := log.Message(2)
		require.NoError(t, err)
		require.Equal(t, "c", message.Text)
		require.NoError(t, log.Close())
	}
}

func TestLogWritesOneFilePerDay(t *testing.T) {
	root := t.TempDir()
	clock := newTestClock()
	log, err := openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

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

	_, err = log.Append("user", "first day")
	require.NoError(t, err)

	clock.now = clock.now.Add(24 * time.Hour)
	_, err = log.Append("user", "second day")
	require.NoError(t, err)

	first, err := os.ReadFile(filepath.Join(root, "main", "2026-01-01.jsonl"))
	require.NoError(t, err)
	require.Equal(t, `{"i":0,"kind":"user","text":"first day","size":9,"date":"2026-01-01T12:00:00Z"}`+"\n", string(first))

	second, err := os.ReadFile(filepath.Join(root, "main", "2026-01-02.jsonl"))
	require.NoError(t, err)
	require.Equal(t, `{"i":1,"kind":"user","text":"second day","size":10,"date":"2026-01-02T12:00:00Z"}`+"\n", string(second))
}

func TestLogAllowsOneWriter(t *testing.T) {
	root := t.TempDir()
	clock := newTestClock()
	log, err := openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

	_, err = openLog(t.Context(), root, clock.Now)
	require.ErrorIs(t, err, errLocked)
	require.NoError(t, log.Close())

	log, err = openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)
	require.NoError(t, log.Close())
}

func TestLogRejectsAnUnknownKind(t *testing.T) {
	log, err := openLog(t.Context(), t.TempDir(), newTestClock().Now)
	require.NoError(t, err)

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

	_, err = log.Append("talk", "text")
	require.ErrorContains(t, err, `unknown message kind "talk"`)
	require.Equal(t, 0, log.Len())
}

func TestLogRejectsAGapInTheIDs(t *testing.T) {
	root := t.TempDir()
	require.NoError(t, os.MkdirAll(filepath.Join(root, "main"), 0o700))

	line := `{"i":1,"kind":"user","text":"x","size":1,"date":"2026-01-01T12:00:00Z"}` + "\n"
	require.NoError(t, os.WriteFile(filepath.Join(root, "main", "2026-01-01.jsonl"), []byte(line), 0o600))

	_, err := openLog(t.Context(), root, newTestClock().Now)
	require.ErrorContains(t, err, "expected message 0, found 1")
}

func TestLogCutsAnIncompleteLastLine(t *testing.T) {
	root := t.TempDir()
	clock := newTestClock()
	log, err := openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

	_, err = log.Append("user", "whole")
	require.NoError(t, err)
	require.NoError(t, log.Close())

	path := filepath.Join(root, "main", "2026-01-01.jsonl")
	file, err := os.OpenFile(path, os.O_WRONLY|os.O_APPEND, 0)
	require.NoError(t, err)

	_, err = file.WriteString(`{"i":1,"kind":"user","te`)
	require.NoError(t, err)
	require.NoError(t, file.Close())

	log, err = openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)
	require.Equal(t, 1, log.Len())

	message, err := log.Append("user", "after the cut")
	require.NoError(t, err)
	require.Equal(t, 1, message.ID)
	require.NoError(t, log.Close())

	log, err = openLog(t.Context(), root, clock.Now)
	require.NoError(t, err)

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

	message, err = log.Message(1)
	require.NoError(t, err)
	require.Equal(t, "after the cut", message.Text)
}

func TestLogRejectsAnIncompleteLineBeforeTheLastDay(t *testing.T) {
	root := t.TempDir()
	require.NoError(t, os.MkdirAll(filepath.Join(root, "main"), 0o700))

	first := `{"i":0,"kind":"user","text":"x","size":1,"date":"2026-01-01T12:00:00Z"}` + "\n" + `{"i":1,"kin`
	second := `{"i":1,"kind":"user","text":"y","size":1,"date":"2026-01-02T12:00:00Z"}` + "\n"
	require.NoError(t, os.WriteFile(filepath.Join(root, "main", "2026-01-01.jsonl"), []byte(first), 0o600))
	require.NoError(t, os.WriteFile(filepath.Join(root, "main", "2026-01-02.jsonl"), []byte(second), 0o600))

	_, err := openLog(t.Context(), root, newTestClock().Now)
	require.ErrorContains(t, err, "ends in an incomplete line")
}

// truncateToOneAndAHalf cuts the index at path in its second record.
func truncateToOneAndAHalf(path string) error {
	return os.Truncate(path, positionBytes+positionBytes/2)
}