package main

import (
	"bufio"
	"encoding/json"
	"image"
	_ "image/jpeg"
	_ "image/png"
	"log"
	"os"
	"path/filepath"
)

// FileEntry contains informations for PowerSlide.
type FileEntry struct {
	Name    string `json:"src"`
	Width   int    `json:"w"`
	Height  int    `json:"h"`
	Caption string `json:"title"`
}

func main() {
	dir, err := os.Getwd()
	if err != nil {
		panic(err)
	}

	entries := buildEntries(dir)

	encodedJSON, err := json.MarshalIndent(entries, "", "  ")
	if err != nil {
		panic(err)
	}

	outputFile, err := os.Create(filepath.Join(dir, "data.json"))
	if err != nil {
		panic(err)
	}
	defer outputFile.Close()

	outputWriter := bufio.NewWriter(outputFile)
	_, err = outputWriter.Write(encodedJSON)
	if err != nil {
		panic(err)
	}
	outputWriter.Flush()
}

func buildEntries(root string) []FileEntry {
	var entries []FileEntry
	filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		ext := filepath.Ext(path)
		if !(ext == ".png" || ext == ".jpg" || ext == ".gif") {
			return nil
		}

		width, height := getImageDimensions(path)
		entries = append(entries, FileEntry{info.Name(), width, height, ""})
		return nil
	})
	return entries
}

func getImageDimensions(path string) (int, int) {
	file, err := os.Open(path)
	if err != nil {
		log.Println(err)
		return 0, 0
	}
	defer file.Close()

	config, _, err := image.DecodeConfig(file)
	if err != nil {
		log.Println(err)
		return 0, 0
	}

	return config.Width, config.Height
}