package bilds

import (
	"errors"
	"fmt"
	"image"
	"os"
	"strconv"
	"strings"

	"github.com/anthonynsimon/bild/imgio"
)

var jpgExtensions = []string{".jpg", ".jpeg"}
var pngExtensions = []string{".png"}
var bmpExtensions = []string{".bmp"}

var (
	// ErrWrongSize is thrown when the provided size string does not match the expected form.
	errWrongSize = errors.New("size must be of form [width]x[height], i.e. 400x200")
)

type size struct {
	Width  int
	Height int
}

func resolveEncoder(outputfile string, defaultEncoding imgio.Encoder) imgio.Encoder {
	lower := strings.ToLower(outputfile)

	for _, ext := range jpgExtensions {
		if strings.HasSuffix(lower, ext) {
			return imgio.JPEGEncoder(100)
		}
	}

	for _, ext := range pngExtensions {
		if strings.HasSuffix(lower, ext) {
			return imgio.PNGEncoder()
		}
	}

	for _, ext := range bmpExtensions {
		if strings.HasSuffix(lower, ext) {
			return imgio.BMPEncoder()
		}
	}

	return defaultEncoding
}

func apply(fin, fout string, process func(image.Image) (image.Image, error)) {
	in, err := imgio.Open(fin)
	exitIfNotNil(err)

	result, err := process(in)
	exitIfNotNil(err)

	encoder := resolveEncoder(fout, imgio.PNGEncoder())
	err = imgio.Save(fout, result, encoder)
	exitIfNotNil(err)
}

func apply2(fin1, fin2, fout string, process func(image.Image, image.Image) (image.Image, error)) {
	in1, err := imgio.Open(fin1)
	exitIfNotNil(err)

	in2, err := imgio.Open(fin2)
	exitIfNotNil(err)

	result, err := process(in1, in2)
	exitIfNotNil(err)

	encoder := resolveEncoder(fout, imgio.PNGEncoder())
	err = imgio.Save(fout, result, encoder)
	exitIfNotNil(err)
}

func exitIfNotNil(err error) {
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}

func parseSizeStr(sizestr string) (*size, error) {
	parts := strings.Split(sizestr, "x")
	if len(parts) != 2 {
		return nil, errWrongSize
	}

	w, err := strconv.Atoi(parts[0])
	if err != nil || w < 0 {
		return nil, errWrongSize
	}

	h, err := strconv.Atoi(parts[1])
	if err != nil || h < 0 {
		return nil, errWrongSize
	}

	return &size{
		Width:  w,
		Height: h,
	}, nil
}