package main

import (
	"bytes"
	"crypto/md5"
	"encoding/hex"
	"errors"
	"flag"
	"fmt"
	"html"
	"io"
	"io/fs"
	"log"
	"os"
	"strings"

	"git.redxen.eu/caskd/goboru"
	"git.redxen.eu/caskd/goboru/modules/gelbooru"
)

func main() {
	var (
		jobs uint
	)
	flag.UintVar(&jobs, "maxjobs", 10, "Maximum concurrent page fetch jobs")
	flag.Parse()

	var (
		media []goboru.Media
		err   error
	)

	if media, err = gelbooru.Query(flag.Args(), 10); err != nil {
		log.Fatal(err)
	}

	log.Print("Fetched ", len(media), " elements")

	for _, v := range media {
		var i uint64
		if i, err = download(v); err != nil {
			log.Fatal(err)
		}
		if i == 0 {
			log.Print("Skipped ", v.MD5)
		} else {
			log.Print("Downloaded ", i, " bytes")
		}
	}
}

func download(m goboru.Media) (i uint64, err error) {
	var (
		f    *os.File
		r    io.ReadCloser
		skip bool
	)

	f, err = os.OpenFile(m.MD5, os.O_RDWR, 0644)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			f, err = os.Create(m.MD5)
			if err != nil {
				err = fmt.Errorf("Failed to create file: %s", err)
				return
			}
		} else {
			err = fmt.Errorf("Failed to open existing file to check MD5 checksum: %s", err)
			return
		}
	} else {
		var md []byte
		md, err = hex.DecodeString(m.MD5)
		if err != nil {
			err = fmt.Errorf("Failed to decode hexadecimal MD5 hash: %s", err)
			return
		}
		h := md5.New()

		_, err = io.Copy(h, f)
		if err != nil {
			err = fmt.Errorf("Failed to copy bytes to intermediate buffer for checksumming: %s", err)
			return
		}
		f.Seek(0, io.SeekStart)

		csum := h.Sum(nil)
		if bytes.Equal(csum, md) {
			skip = true
		} else {
			log.Printf("Hash mismatch: %x != %x [%s]", csum, md, m.Source)
		}
	}

	if !skip {
		r, err = m.Content()
		if err != nil {
			err = fmt.Errorf("Failed to get content reader: %s", err)
			return
		}

		var ir int64
		ir, err = io.Copy(f, r)
		i = uint64(ir)
		if err != nil {
			err = fmt.Errorf("Failed to copy bytes to file: %s", err)
			return
		}
		r.Close()
	}
	f.Close()

	for _, x := range m.Tags {
		x = html.UnescapeString(x)          // Unescape tags
		x = strings.ReplaceAll(x, "/", "_") // Replace filesystem delimiters in tags

		err = os.Mkdir(x, 0750)
		if err != nil {
			if !os.IsExist(err) {
				err = fmt.Errorf("Failed to create tag directory %s: %v", x, err)
				return
			}
		}

		src, dst := strings.Join([]string{x, m.MD5}, "/"), strings.Join([]string{"..", m.MD5}, "/")
		err = os.Symlink(dst, src)
		if err != nil {
			if !os.IsExist(err) {
				err = fmt.Errorf("Failed to create symlink in tag directory %s: %v", src, err)
				return
			}
		}
	}
	err = nil
	return
}