package main

import (
  "os"
  "image"
  "encoding/json"
  "log"
  "image/png"
  "github.com/disintegration/gift"
  "flag"
  "lcthw.dev/go/jankifier/filters"
)

func LoadImage(filename string) image.Image {
  reader, err := os.Open(filename)
  if err != nil { log.Fatal(err) }
  defer reader.Close()

  img, _, err := image.Decode(reader)
  if err != nil { log.Fatal(err) }

  return img
}

func SaveImage(filename string, img image.Image) {
  out, err := os.Create(filename)
  if err != nil {
    log.Fatalf("can't write file %s: %v", filename, err)
  }
  defer out.Close()

  err = png.Encode(out, img)
  if err != nil {
    log.Fatalf("can't png encode %s: %v", filename, err)
  }
}

type Opts struct {
  Config string
  Force bool
}

type Conversion struct {
  PixelWidth int
  ColorDepth int
  DitherType int
  Width int
  Height int
}

type Settings struct {
  Source string
  Target string
  Base Conversion
  Exceptions map[string]Conversion
}

func LoadSettings(path string) Settings {
  var settings Settings

  config, err := os.ReadFile(path)
  if err != nil {
      log.Fatalf("invalid config path: %s", path)
  }

  err = json.Unmarshal(config, &settings)
  if err != nil {
      log.Fatalf("json format error:", err)
  }

  return settings
}

func ParseOpts() Opts {
  var opts Opts

  flag.StringVar(&opts.Config, "config", "config.json", "config file")
  flag.BoolVar(&opts.Force, "force", false, "force a full convert")
  flag.Parse()

  return opts
}

func JankImage(settings Conversion, in_file string, out_file string) {
  src := LoadImage(in_file)
  bounds := src.Bounds()

  resize := gift.Resize(bounds.Max.X / settings.PixelWidth, 0, gift.NearestNeighborResampling)
  posterize := filters.Posterize(uint16(settings.ColorDepth), settings.DitherType)
  upscale := filters.Upscale(bounds, settings.PixelWidth)
  sharpen := gift.UnsharpMask(1, 1, 0)

  g := gift.New(resize, posterize, upscale, sharpen)
  out_img := image.NewNRGBA(g.Bounds(bounds))
  g.Draw(out_img, src)

  SaveImage(out_file, out_img)
}

func main() {
  opts := ParseOpts()
  settings := LoadSettings(opts.Config)
  JankImage(settings.Base, settings.Source, settings.Target)
}