package main

import (
	"bytes"
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io/fs"
	"io/ioutil"
	"log"
	"os"
	"os/signal"
	"path"
	"regexp"
	"strings"
	"syscall"
	"text/template"

	yaml "gopkg.in/yaml.v3"
)

var (
	Debug         = os.Getenv("DEBUG") == "true"
	ConstTitle    = os.Getenv("YAML_C_TITLE")
	ConstSeason   = os.Getenv("YAML_C_SEASON")
	ConstEpisode  = os.Getenv("YAML_C_EPISODE")
	ConstOutd     = os.Getenv("YAML_O")
	Dry           = os.Getenv("YAML_D") == "true" || os.Getenv("DRY") == "true"
	ConstPatterns = os.Getenv("YAML_P")
)

type Yaml struct {
	C Fields
	O string
	D bool
	P []string
}

const YamlFile = ".show-ingestion.yaml"

type Fields struct {
	Title   string
	Season  string
	Episode string
}

type MvNLn func(string, string) error

func main() {
	ctx, can := signal.NotifyContext(context.Background(), syscall.SIGINT)
	defer can()

	foo := Main
	if len(os.Args) == 2 && os.Args[1] == "r" {
		foo = Recursive
	} else if len(os.Args) == 2 && os.Args[1] == "i" {
		foo = Stage
	}
	if err := foo(ctx); err != nil {
		panic(err)
	}
}

func Stage(ctx context.Context) error {
	if _, err := os.Stat(YamlFile); err == nil {
		return nil
	}
	b, _ := yaml.Marshal(Yaml{
		D: true,
		O: "/volume1/video/Bel/Anime/{{.Title}}/Season_{{.Season}}",
	})
	return ioutil.WriteFile(YamlFile, b, os.ModePerm)
}

func Recursive(ctx context.Context) error {
	q := []string{"./"}
	for len(q) > 0 {
		d := q[0]
		q = q[1:]

		p := path.Join(d, YamlFile)
		if _, err := os.Stat(p); err != nil {
		} else if err := func() error {
			y, err := NewYaml(path.Join(d, YamlFile))
			if err != nil {
				return err
			}

			was, err := os.Getwd()
			if err != nil {
				return err
			}

			if err := os.Chdir(d); err != nil {
				return err
			}
			defer os.Chdir(was)

			log.Printf("Run(outd=%s, ind=%s, patterns=%+v, const=%+v, dry=%v)", y.O, d, y.P, y.C, y.D)
			if err := Run(ctx, y.O, "./", y.P, y.C, y.D); err != nil {
				return err
			}

			return os.Chdir(was)
		}(); err != nil {
			return fmt.Errorf("%s: %w", p, err)
		}

		entries, err := readDir(d)
		if err != nil {
			return err
		}
		for _, entry := range entries {
			if entry.IsDir() {
				q = append(q, path.Join(d, entry.Name()))
			}
		}
	}
	return nil
}

func Main(ctx context.Context) error {
	flags := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
	overridesS := flags.String("c", `{"title":"","season":"","episode":""}`, "overrides")
	ind := flags.String("i", "/dev/null", "in dir")
	outd := flags.String("o", "/dev/null", "out dir template accepts overrides format title case")
	dry := flags.Bool("d", true, "dry run")
	if err := flags.Parse(os.Args[1:]); err != nil {
		panic(err)
	}

	var overrides Fields
	json.Unmarshal([]byte(*overridesS), &overrides)

	return Run(ctx,
		*outd,
		*ind,
		flags.Args(),
		overrides,
		*dry,
	)
}

const (
	PatternGroupTitleHyphenSEDual = `^(\[[^\]]*\] )?(?P<title>.*?)( -)?[ \.](S(?P<season>[0-9]{2})E)?(?P<episode>[0-9]{2})[^0-9].*[dD][uU][aA][lL].*`
	PatternGroupTitleHyphenSE     = `^(\[[^\]]*\] )?(?P<title>.*?)( -)?[ \.](S(?P<season>[0-9]{2})E)?(?P<episode>[0-9]{2})[^0-9].*`
	PatternTitleSEDual            = `^(?P<title>.*) S(?P<season>[0-9]+)E(?P<episode>[0-9]+).*[dD][uU][aA][lL].*`
	PatternTitleSE                = `^(?P<title>.*) S(?P<season>[0-9]+)E(?P<episode>[0-9]+).*`
	SEDual                        = `^S(?P<season>[0-9]+)E(?P<episode>[0-9]+).*[dD][uU][aA][lL].*`
	SE                            = `^S(?P<season>[0-9]+)E(?P<episode>[0-9]+).*`
)

func Run(ctx context.Context, outd, ind string, patterns []string, overrides Fields, dry bool) error {
	mvNLn := RealMvNLn
	if dry {
		mvNLn = DryMvNLn()
	}
	return RunWith(ctx,
		outd,
		ind,
		append(patterns,
			PatternGroupTitleHyphenSEDual,
			PatternGroupTitleHyphenSE,
			PatternTitleSEDual,
			PatternTitleSE,
			SEDual,
			SE,
		),
		overrides,
		mvNLn,
	)
}

func RunWith(ctx context.Context, outd, ind string, patterns []string, overrides Fields, mvNLn MvNLn) error {
	entries, err := readDir(ind)
	if err != nil {
		return err
	}
	for _, pattern := range patterns {
		for _, entry := range entries {
			if !entry.Type().IsRegular() && !(Debug && Dry) {
				continue
			}
			if err := one(ctx, outd, path.Join(ind, entry.Name()), []string{pattern}, overrides, mvNLn); err != nil {
				return err
			}
		}
	}
	return nil
}

func one(ctx context.Context, outd, inf string, patterns []string, overrides Fields, mvNLn MvNLn) error {
	f := path.Base(inf)
	for _, pattern := range patterns {
		found, match := Parse(f, pattern)
		if !match {
			continue
		}

		for _, wr := range [][2]*string{
			[2]*string{&found.Title, &overrides.Title},
			[2]*string{&found.Season, &overrides.Season},
			[2]*string{&found.Episode, &overrides.Episode},
		} {
			if *wr[1] != "" {
				*wr[0] = *wr[1]
			}
		}

		if found.Title == "" || found.Season == "" || found.Episode == "" {
			continue
		}
		found.Title = strings.ReplaceAll(found.Title, ".", " ")
		found.Title = strings.Join(strings.Fields(found.Title), "_")

		return foundOne(ctx, outd, inf, found, mvNLn)
	}
	return nil
}

func Parse(f string, pattern string) (Fields, bool) {
	re := regexp.MustCompile(pattern)
	if !re.MatchString(f) {
		return Fields{}, false
	}

	var found Fields
	groupNames := re.SubexpNames()
	groups := re.FindStringSubmatch(f)
	for i := 1; i < len(groupNames); i++ {
		v := groups[i]
		switch groupNames[i] {
		case "title":
			found.Title = v
		case "season":
			found.Season = v
		case "episode":
			found.Episode = v
		default:
			//return fmt.Errorf("unexpected capture group %q", groupNames[i])
		}
	}
	return found, true
}

func foundOne(ctx context.Context, outd, inf string, fields Fields, mvNLn MvNLn) error {
	tmpl, err := template.New(inf).Parse(outd)
	if err != nil {
		return err
	}
	buff := bytes.NewBuffer(nil)
	if err := tmpl.Execute(buff, fields); err != nil {
		return err
	}

	outf := path.Join(string(buff.Bytes()), fmt.Sprintf("%s_S%sE%s%s", fields.Title, fields.Season, fields.Episode, path.Ext(inf)))
	return mvNLn(outf, inf)
}

func RealMvNLn(outf, inf string) error {
	if stat, err := os.Stat(inf); err != nil || !stat.Mode().IsRegular() {
		return fmt.Errorf("cannot mv_n_ln(%s): (%v) mode=%v", inf, err, stat.Mode())
	}
	if _, err := os.Stat(outf); err == nil {
		return nil
	}
	if err := os.MkdirAll(path.Dir(outf), os.ModePerm); err != nil {
		return err
	}
	if err := os.Rename(inf, outf); err != nil {
		return err
	}
	return os.Symlink(outf, inf)
}

func DryMvNLn() func(string, string) error {
	outd := map[string]struct{}{}
	return func(outf, inf string) error {
		if _, err := os.Stat(outf); err == nil {
			if Debug {
				fmt.Fprintf(os.Stderr, "no mv %q\n      %q\n", inf, outf)
			}
			return nil
		}

		if _, ok := outd[outf]; ok {
			if Debug {
				fmt.Fprintf(os.Stderr, "no mv %q\n      %q\n", inf, outf)
			}
			return nil
		}
		outd[outf] = struct{}{}

		fmt.Fprintf(os.Stderr, "mv %q\n   %q\n", inf, outf)
		return nil
	}
}

func readDir(d string) ([]fs.DirEntry, error) {
	entries, err := os.ReadDir(d)
	result := []fs.DirEntry{}
	for _, entry := range entries {
		if !strings.HasPrefix(entry.Name(), ".") {
			result = append(result, entry)
		}
	}
	return result, err
}

func NewYaml(p string) (Yaml, error) {
	var y Yaml
	b, _ := os.ReadFile(p)
	if err := yaml.Unmarshal(b, &y); err != nil {
		return y, fmt.Errorf("%s: %w", p, err)
	}

	if ConstTitle != "" {
		y.C.Title = ConstTitle
	}
	if ConstSeason != "" {
		y.C.Season = ConstSeason
	}
	if ConstEpisode != "" {
		y.C.Episode = ConstEpisode
	}

	if ConstOutd != "" {
		y.O = ConstOutd
	}

	if Dry {
		y.D = true
	}

	if ConstPatterns != "" {
		y.P = strings.Split(ConstPatterns, ",")
	}

	return y, nil
}