// Run a command whenever a file is modified.

package main

import (
	"flag"
	"fmt"
	"os"
	"os/exec"
	"runtime/debug"
	"strings"
	"time"

	"github.com/fsnotify/fsnotify"
)

// Colors in escape sequences
var (
	Reset = "\033[0m"
	Cyan  = "\033[36m"
)

var (
	// Path in which to look for commands
	Path string
	// Command run for building
	BuildCommand []string
	// Command run after build
	RunCommand []string
	// Command will only run on files that have the Suffixes extension
	Suffixes []string
	// Layout for timestamp of command
	DateLayout string = "15:04:05"
	// Version tag for wbr
	Version string
)

func GetVersion() string {
	if Version != "" {
		return Version
	}
	buildinfo, ok := debug.ReadBuildInfo()
	if !ok {
		panic("Could not read buildinfo to know package version.")
	}
	return buildinfo.Main.Version
}

func CompileRun(fileName string) {
	found := false
	for _, Ext := range Suffixes {
		if strings.HasSuffix(fileName, Ext) {
			found = true
			break
		}
	}
	if !found {
		return
	}

	// Build the program, exit if return if there was an error
	if len(BuildCommand) > 0 && BuildCommand[0] != "" {
		var buildCmd *exec.Cmd
		if len(BuildCommand) > 1 {
			buildCmd = exec.Command(BuildCommand[0], append(BuildCommand[1:], fileName)...)
		} else {
			buildCmd = exec.Command(BuildCommand[0], fileName)
		}
		// run the build command
		out, err := buildCmd.CombinedOutput()

		date := time.Now().Format(DateLayout)
		if len(BuildCommand) > 1 {
			fmt.Printf("[%s %s%s %s%s]\n", date, Cyan, BuildCommand[0], strings.Join(append(BuildCommand[1:], fileName), " "), Reset)
		} else {
			fmt.Printf("[%s %s%s %s %s%s]\n", date, Cyan, BuildCommand[0], BuildCommand, fileName, Reset)
		}

		if len(out) > 0 {
			fmt.Printf("%s", out)
		}

		if err != nil {
			if _, ok := err.(*exec.ExitError); ok {
				return
			} else if !ok {
				panic(err)
			}
		}
	}

	if len(RunCommand) > 0 && RunCommand[0] != "" {
		// There was no error in the build so we can execute the run command
		var runCmd *exec.Cmd
		if len(RunCommand) > 1 {
			runCmd = exec.Command(RunCommand[0], RunCommand[1:]...)
		} else {
			runCmd = exec.Command(RunCommand[0])
		}

		date := time.Now().Format(DateLayout)
		out, err := runCmd.CombinedOutput()
		if len(RunCommand) > 1 {
			fmt.Printf("[%s %s%s %s%s]\n", date, Cyan, RunCommand[0], strings.Join(RunCommand[1:], " "), Reset)
		} else {
			fmt.Printf("[%s %s%s%s]\n", date, Cyan, RunCommand[0], Reset)

		}
		if len(out) > 0 {
			fmt.Printf("%s", out)
		}

		if err != nil {
			if _, ok := err.(*exec.ExitError); ok {
				return
			} else if !ok {
				panic(err)
			}
		}
	}

}

func main() {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		panic(err)
	}
	defer watcher.Close()

	bc := flag.String("b", "", "Command to run for building, it will pass the file modified as argument to it")
	rc := flag.String("r", "", "Command for running after build")
	s := flag.String("s", "", "Filter watched files by suffix, specify multiple by separating with ','")
	p := flag.String("p", ".", "Path to watch for files")
	v := flag.Bool("v", false, "Show wbr version")
	flag.Parse()

	if *v {
		fmt.Printf("wbr %s\n", GetVersion())
		os.Exit(0)
	}

	BuildCommand = strings.Split(*bc, " ")
	RunCommand = strings.Split(*rc, " ")
	Suffixes = strings.Split(*s, ",")
	Path = *p

	fmt.Printf("[%s watching '%s'%s]\n", Cyan, Path, Reset)

	go func() {
		for {
			select {
			case event, ok := <-watcher.Events:
				if !ok {
					return
				}
				if event.Has(fsnotify.Write) {
					CompileRun(event.Name)
				}
			case err, ok := <-watcher.Errors:
				if !ok {
					return
				}
				fmt.Println("error:", err)
			}
		}
	}()

	err = watcher.Add(Path)
	if err != nil {
		panic(err)
	}

	<-make(chan struct{})
}