package xdgIcons

import "os"
import "fmt"
import "log"
import "image"
import "regexp"
import "strings"
import _ "image/png"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/data"
import "git.tebibyte.media/tomo/tomo/canvas"
import "git.tebibyte.media/tomo/backend/style"
import xdgIconTheme "git.tebibyte.media/tomo/xdg/icon-theme"

type iconTheme struct {
	xdg xdgIconTheme.Theme
	fallback       style.IconSet
	texturesSmall  map[tomo.Icon] canvas.Texture
	texturesMedium map[tomo.Icon] canvas.Texture
	texturesLarge  map[tomo.Icon] canvas.Texture
}

func FindThemeWarn (name string, fallback style.IconSet, path ...string) (style.IconSet, error) {
	this := &iconTheme {
		fallback:       fallback,
		texturesLarge:  make(map[tomo.Icon] canvas.Texture),
		texturesMedium: make(map[tomo.Icon] canvas.Texture),
		texturesSmall:  make(map[tomo.Icon] canvas.Texture),
	}
	
	xdg, err := xdgIconTheme.FindThemeWarn(name, path...)
	if err != nil { return nil, err }
	this.xdg = xdg
	
	return this, nil
}

func (this *iconTheme) selectSource (size tomo.IconSize) map[tomo.Icon] canvas.Texture {
	switch size {
	case tomo.IconSizeMedium: return this.texturesMedium
	case tomo.IconSizeLarge:  return this.texturesLarge
	default:                  return this.texturesSmall
	}
}

func (this *iconTheme) xdgIcon (name string, size tomo.IconSize) (canvas.Texture, bool) {
	// TODO use scaling factor instead of 1
	// find icon file
	icon, err := this.xdg.FindIcon(name, iconSizePixels(size), 1, xdgIconTheme.PNG)
	if err != nil { return nil, false }

	// open icon file
	iconFile, err := os.Open(icon.Path)
	if err != nil {
		// this failing indicates a broken icon theme
		log.Printf("nasin: icon file '%s' is inaccessible: %v\n", icon.Path, err)
		return nil, false
	}

	iconImage, _, err := image.Decode(iconFile)
	if err != nil {
		// this failing indicates a broken icon theme
		log.Printf("nasin: icon file '%s' is broken: %v\n", icon.Path, err)
		return nil, false
	}

	return tomo.NewTexture(iconImage), true
}

func (this *iconTheme) Icon (icon tomo.Icon, size tomo.IconSize) canvas.Texture {
	source := this.selectSource(size)
	texture, ok := source[icon]
	if !ok {
		texture = this.icon(icon, size)
		source[icon] = texture
	}

	if texture == nil {
		return this.fallback.Icon(icon, size)
	} else {
		return texture
	}
}

func (this *iconTheme) MimeIcon (mime data.Mime, size tomo.IconSize) canvas.Texture {
	icon := tomo.Icon(mime.String())
	source := this.selectSource(size)
	texture, ok := source[icon]
	if !ok {
		texture = this.mimeIcon(mime, size)
		source[icon] = texture
	}

	if texture == nil {
		return this.fallback.MimeIcon(mime, size)
	} else {
		return texture
	}
}

func (this *iconTheme) icon (icon tomo.Icon, size tomo.IconSize) canvas.Texture {
	if texture, ok := this.xdgIcon(XdgIconName(icon), size); ok {
		return texture
	}
	if texture, ok := this.xdgIcon(XdgIconName(generalizeIcon(icon)), size); ok {
		return texture
	}
	return nil
}

func (this *iconTheme) mimeIcon (mime data.Mime, size tomo.IconSize) canvas.Texture {
	if texture, ok := this.xdgIcon(xdgFormatMime(mime), size); ok {
		return texture
	}
	if texture, ok := this.xdgIcon(xdgFormatMime(generalizeMimeType(mime)), size); ok {
		return texture
	}
	if texture, ok := this.xdgIcon(xdgFormatMime(data.M("text", "x-generic")), size); ok {
		return texture
	}
	return nil
}

var kebabMatchFirstCap = regexp.MustCompile("(.)([A-Z][a-z]+)")
var kebabMatchAllCaps  = regexp.MustCompile("([a-z0-9])([A-Z])")

// XdgIconName returns the best XDG name for the given icon.
func XdgIconName (icon tomo.Icon) string {
	if name, ok := xdgIconNames[icon]; ok {
		return name
	}

	name := kebabMatchFirstCap.ReplaceAllString(string(icon), "${1}-${2}")
	name  = kebabMatchAllCaps.ReplaceAllString(string(name), "${1}-${2}")
	return strings.ToLower(name)
}

func generalizeIcon (icon tomo.Icon) tomo.Icon {
	name := string(icon)
	switch {
	case strings.HasPrefix(name, "Application"): return tomo.IconApplication
	case strings.HasPrefix(name, "Preferences"): return tomo.IconPreferences
	case strings.HasPrefix(name, "Device"):      return tomo.IconDevice
	case strings.HasPrefix(name, "Hardware"):    return tomo.IconHardware
	case strings.HasPrefix(name, "Storage"):     return tomo.IconStorageHardDisk
	case strings.HasPrefix(name, "Input"):       return tomo.IconInputMouse
	case strings.HasPrefix(name, "Network"):     return tomo.IconNetworkWired
	case strings.HasPrefix(name, "Place"):       return tomo.IconPlaceDirectory
	case strings.HasPrefix(name, "Directory"):   return tomo.IconPlaceDirectory
	case strings.HasPrefix(name, "Trash"):       return tomo.IconPlaceTrash
	case strings.HasPrefix(name, "Help"):        return tomo.IconHelpContents
	}

	switch icon {
	case tomo.IconCellularSignal0: return tomo.IconWirelessSignal0
	case tomo.IconCellularSignal1: return tomo.IconWirelessSignal1
	case tomo.IconCellularSignal2: return tomo.IconWirelessSignal2
	case tomo.IconCellularSignal3: return tomo.IconWirelessSignal3
	}

	return icon
}

func xdgFormatMime (mime data.Mime) string {
	return fmt.Sprintf("%s-%s", mime.Type, mime.Subtype)
}

func generalizeMimeType (mime data.Mime) data.Mime {
	// FIXME make this more accurate
	// https://specifications.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html
	mime.Subtype = "x-generic"
	return mime
}

func iconSizePixels (size tomo.IconSize) int {
	// TODO: once Tomo has scaling support, take that into account here
	switch size {
	case tomo.IconSizeMedium: return 24
	case tomo.IconSizeLarge:  return 48
	default:                  return 16
	}
}