// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

package spellcheck

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"reflect"
	"syscall"
	"testing"
	"time"
)

func TestExceptionEditsPreserveOtherReadersChanges(t *testing.T) {
	path := filepath.Join(t.TempDir(), "exceptions.json")
	options := Options{ExceptionsPath: path, OpenDictionary: func(string) (Dictionary, error) { return &TestDictionary{}, nil }}
	first, second := New_service(context.Background(), options), New_service(context.Background(), options)
	defer first.Close()
	defer second.Close()
	// Both readers load the original list, then the user switches between them.
	receive_result(t, first, Request{Operation: Inspect})
	receive_result(t, second, Request{Operation: Inspect})
	for _, edit := range []struct {
		service *Service
		request Request
		want    []string
	}{
		{first, Request{Operation: Add, Word: "Alpha"}, []string{"Alpha"}},
		{second, Request{Operation: Add, Word: "Beta"}, []string{"Alpha", "Beta"}},
		{first, Request{Operation: Remove, Word: "ALPHA"}, []string{"Beta"}},
		{second, Request{Operation: Add, Word: "Gamma"}, []string{"Beta", "Gamma"}},
		{first, Request{Operation: Add, Word: "Alpha"}, []string{"Alpha", "Beta", "Gamma"}},
	} {
		result := receive_result(t, edit.service, edit.request)
		if result.Err != nil || !reflect.DeepEqual(result.Exceptions, edit.want) {
			t.Fatalf("edit %v: result=%+v, want=%v", edit.request, result, edit.want)
		}
		words, err := load_exceptions(path)
		if err != nil || !reflect.DeepEqual(exception_list(words), edit.want) {
			t.Fatalf("saved exceptions=%v, error=%v, want=%v", words, err, edit.want)
		}
	}
}

// Separate processes verify that the transaction lock works across readers.
func TestExceptionWriterProcess(t *testing.T) {
	path := os.Getenv("FENRIR_EXCEPTION_TEST_PATH")
	if path == "" {
		return
	}
	service := New_service(context.Background(), Options{ExceptionsPath: path, OpenDictionary: func(string) (Dictionary, error) { return &TestDictionary{}, nil }})
	defer service.Close()
	encoder, decoder := json.NewEncoder(os.Stdout), json.NewDecoder(os.Stdin)
	result := receive_result(t, service, Request{Operation: Inspect})
	if result.Err != nil {
		t.Fatal(result.Err)
	}
	if err := encoder.Encode(result.Exceptions); err != nil {
		t.Fatal(err)
	}
	for {
		var request Request
		if err := decoder.Decode(&request); err != nil {
			if errors.Is(err, io.EOF) {
				return
			}
			t.Fatal(err)
		}
		result := receive_result(t, service, request)
		if result.Err != nil {
			t.Fatal(result.Err)
		}
		if err := encoder.Encode(result.Exceptions); err != nil {
			t.Fatal(err)
		}
	}
}

func TestConcurrentExceptionProcessesKeepBothEdits(t *testing.T) {
	path := filepath.Join(t.TempDir(), "exceptions.json")
	type Writer struct {
		encoder *json.Encoder
		decoder *json.Decoder
	}
	start_writer := func() Writer {
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		cmd := exec.CommandContext(ctx, os.Args[0], "-test.run=^TestExceptionWriterProcess$")
		cmd.Env = append(os.Environ(), "FENRIR_EXCEPTION_TEST_PATH="+path)
		cmd.Stderr = os.Stderr
		input, err := cmd.StdinPipe()
		if err != nil {
			cancel()
			t.Fatal(err)
		}
		output, err := cmd.StdoutPipe()
		if err != nil {
			cancel()
			t.Fatal(err)
		}
		if err := cmd.Start(); err != nil {
			cancel()
			t.Fatal(err)
		}
		t.Cleanup(func() {
			input.Close()
			err := cmd.Wait()
			cancel()
			if err != nil {
				t.Error(err)
			}
		})
		writer := Writer{json.NewEncoder(input), json.NewDecoder(output)}
		var ready []string
		if err := writer.decoder.Decode(&ready); err != nil {
			t.Fatal(err)
		}
		return writer
	}
	first, second := start_writer(), start_writer()
	for _, edit := range []struct {
		writer Writer
		word   string
	}{{first, "Alpha"}, {second, "Beta"}} {
		if err := edit.writer.encoder.Encode(Request{Operation: Add, Word: edit.word}); err != nil {
			t.Fatal(err)
		}
	}
	for _, writer := range []Writer{first, second} {
		var words []string
		if err := writer.decoder.Decode(&words); err != nil {
			t.Fatal(err)
		}
	}
	words, err := load_exceptions(path)
	if err != nil || !reflect.DeepEqual(exception_list(words), []string{"Alpha", "Beta"}) {
		t.Fatal("lost concurrent addition", words, err)
	}
	info, err := os.Stat(path + ".lock")
	if err != nil || info.Mode().Perm() != 0600 {
		t.Fatal("lock permissions", info, err)
	}
}

func TestExceptionLockCancellationAndInvalidStorePreserveData(t *testing.T) {
	path := filepath.Join(t.TempDir(), "exceptions.json")
	if err := save_exceptions(path, map[string]string{"alpha": "Alpha"}); err != nil {
		t.Fatal(err)
	}
	lock, err := os.OpenFile(path+".lock", os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		t.Fatal(err)
	}
	defer lock.Close()
	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX); err != nil {
		t.Fatal(err)
	}
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
	defer cancel()
	if _, err := update_exceptions(ctx, path, Add, "Beta"); !errors.Is(err, context.DeadlineExceeded) {
		t.Fatal("lock wait ignored cancellation", err)
	}
	words, err := load_exceptions(path)
	if err != nil || !reflect.DeepEqual(exception_list(words), []string{"Alpha"}) {
		t.Fatal("cancelled edit changed data", words, err)
	}
	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_UN); err != nil {
		t.Fatal(err)
	}
	if _, err := update_exceptions(context.Background(), path, Add, "Beta"); err != nil {
		t.Fatal("edit failed after lock release", err)
	}
	if err := os.WriteFile(path, []byte("invalid JSON"), 0600); err != nil {
		t.Fatal(err)
	}
	if _, err := update_exceptions(context.Background(), path, Add, "Gamma"); err == nil {
		t.Fatal("edit overwrote invalid shared file")
	}
	data, err := os.ReadFile(path)
	if err != nil || string(data) != "invalid JSON" {
		t.Fatal("invalid file was replaced", string(data), err)
	}
}