package main

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"slices"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/fsnotify/fsnotify"
	"github.com/jessevdk/go-flags"

	"alin.ovh/erl/command"
	"alin.ovh/erl/ignore"
	"alin.ovh/erl/state"
	"alin.ovh/erl/watcher"
)

type Options struct {
	Exec    string `short:"x" long:"exec"    description:"command to execute on file change"`
	Quiet   bool   `short:"q" long:"quiet"   description:"suppress own output"`
	Verbose bool   `short:"v" long:"verbose" description:"verbose output (print events)"`
}

func Start(ctx context.Context, verbose *log.Logger, w watcher.Watcher, sm *state.StateMachine) {
	var wg sync.WaitGroup

	wg.Add(1)
	go func(events <-chan watcher.Event, errors <-chan error) {
		defer wg.Done()
		sm.SendEvent(state.Start)
		for {
			select {
			case <-ctx.Done():
				sm.SendEvent(state.Signal)

				return
			case event, ok := <-events:
				if !ok {
					return
				}

				// skip if _only_ chmod
				if event.Op == fsnotify.Chmod {
					continue
				}

				verbose.Printf("event: %s %s\n", event.Name, event.Op.String())
				if event.Op.Has(fsnotify.Create) {
					stat, err := os.Stat(event.Name)
					if err != nil {
						log.Printf("Error getting file info: %v\n", err)

						continue
					}
					if stat.IsDir() {
						err = w.AddRecursive(event.Name)
						if err != nil {
							log.Printf("Error adding directory to watcher: %v\n", err)
						}
					}
				}
				if event.Op.Has(fsnotify.Remove) {
					for _, dir := range w.WatchList() {
						if strings.HasPrefix(dir, event.Name) {
							err := w.Remove(dir)
							if err != nil {
								log.Printf("Error removing directory from watcher: %v\n", err)
							}
						}
					}
				}

				sm.SendEvent(state.Restart)

				time.Sleep(100 * time.Millisecond)

			case err, ok := <-errors:
				if !ok {
					return
				}
				log.Printf("Error: %v\n", err)
			}
		}
	}(w.Monitor())

	err := w.AddRecursive(".")
	if err != nil {
		log.Fatalf("failed to add directory to watcher: %v", err)
	}

	<-ctx.Done()
	log.Println("shutting down")

	sm.SendEvent(state.Signal)

	wg.Wait()
}

func main() {
	var opts Options
	log.SetFlags(log.Lmsgprefix)

	fp := flags.NewParser(&opts, flags.Default)
	args, err := fp.Parse()
	if err != nil {
		if errors.Is(err, flags.ErrHelp) {
			os.Exit(0)
		}

		log.Fatalf("failed to parse flags: %v", err)
	}

	program := opts.Exec
	if program == "" {
		program = "go"

		if len(args) == 0 {
			args = []string{"run", "."}
		} else {
			args = slices.Insert(args, 0, "run")
		}
	}

	wd, err := os.Getwd()
	if err != nil {
		log.Fatalf("failed to get working directory: %v", err)
	}

	ctx, cancel := signal.NotifyContext(
		context.Background(),
		os.Interrupt,
		syscall.SIGHUP,
		syscall.SIGTERM,
	)
	defer cancel()

	filter := ignore.New(wd)
	err = filter.ReadIgnoreFiles(ctx)
	if err != nil {
		panic(fmt.Sprintf("failed to read ignore files: %v", err))
	}

	watcher, err := watcher.New(watcher.Options{
		Filter: *filter,
	})
	if err != nil {
		panic(fmt.Sprintf("failed to create watcher: %v", err))
	}
	defer watcher.Close()

	copts := command.Options{}
	if opts.Quiet {
		copts.Output = io.Discard
	}

	var logger *log.Logger
	if opts.Verbose {
		logger = log.New(os.Stderr, "", 0)
	} else {
		logger = log.New(io.Discard, "", 0)
	}

	cmd := command.New(program, args, copts)
	sm := state.New(cmd, log.New(os.Stderr, "state: ", log.Lmsgprefix))
	Start(ctx, logger, watcher, sm)
}