package emoji

import (
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"unicode/utf8"
)

// Emoji is a node of a Table
type Emoji struct {
	Codepoint []rune
	IsEmoji   bool
	Path      string
	Sub       Table
}

func (e Emoji) String() (str string) {
	str = "Emoji("
	for _, cprune := range e.Codepoint {
		str += fmt.Sprintf("%U ", cprune)
	}
	str = strings.TrimRight(str, " ") + ")"
	if e.Sub != nil {
		str += "+"
	}
	if e.IsEmoji {
		str += fmt.Sprintf("\n  └ Path: %s", e.Path)
	}
	return str + "\n"
}

// Length returns the lenght of the emoji in bytes
func (e Emoji) Length() int {
	total := 0
	for _, r := range e.Codepoint {
		total += utf8.RuneLen(r)
	}
	return total
}

// Table is a table of detected Unicode codepoints sequences for which an emoticon is available
type Table map[rune]Emoji

// Find checks if a given strings begins with an emoji made by one or more sequential runes
func (em Table) Find(str string) *Emoji {
	for i, r := range str {
		e, ok := em[r]
		if !ok {
			break
		}
		// Check if there are more bytes to check
		if len(str) > i && e.Sub != nil {
			rlen := utf8.RuneLen(r)
			newemj := e.Sub.Find(str[i+rlen:])
			if newemj != nil {
				return newemj
			}
		}
		if e.IsEmoji {
			return &e
		}
	}
	return nil
}

// IsEmoji checks whether the given rune is an emoji
func (em Table) IsEmoji(cp rune) bool {
	_, ok := em[cp]
	return ok
}

func (em Table) tostring(indent string, nomarker bool) (str string) {
	counter := len(em)
	marker := "│ "
	if nomarker {
		marker = "  "
	}
	for r, emo := range em {
		listr := "├"
		if counter == 1 {
			listr = "└"
		}
		str += fmt.Sprintf(indent+"%s%s %U", marker, listr, r)
		if emo.IsEmoji {
			str += fmt.Sprintf(": %s", emo.Path)
		}
		str += "\n"
		if emo.Sub != nil {
			str += emo.Sub.tostring(indent+marker, counter == 1)
		}
		counter--
	}
	return
}

func (em Table) String() string {
	return "Emoji table\n" + em.tostring("", true)
}

// ScanEmojiDirectory scans a directory for images to use as icons
// Pictures must be named in this format:
//    emoji_uXXXX_XXXX.png
// where XXXX are Unicode codepoints
// See <https://github.com/googlei18n/noto-emoji/tree/master/png/128>
func ScanEmojiDirectory(emojipath string) (tab Table, err error) {
	tab = make(Table)
	err = filepath.Walk(emojipath, func(path string, info os.FileInfo, err error) error {
		// Ignore non-images
		if !strings.HasSuffix(strings.ToLower(path), ".png") {
			return nil
		}

		// Get icon filename
		emojiname := filepath.Base(path)

		// Strip prefix and suffix
		extsep := strings.LastIndexByte(emojiname, '.')
		basesep := strings.IndexByte(emojiname, '_')
		codepointstr := emojiname[basesep+2 : extsep]

		// Split codepoints by separator (_)
		codepointlist := strings.Split(codepointstr, "_")

		// Parse codepoints to runes
		curtab := &tab
		codepoints := []rune{}
		for cpi, cpstr := range codepointlist {
			num, err := strconv.ParseInt(cpstr, 16, 32)
			if err != nil {
				return fmt.Errorf("malformed icon filename: %s (codepoints are not valid int32)", emojiname)
			}
			cprune := rune(num)
			newemo := (*curtab)[cprune]
			codepoints = append(codepoints, cprune)
			newemo.Codepoint = codepoints[:]
			if len(codepointlist) < cpi+2 {
				// Set as emoji
				newemo.IsEmoji = true
				newemo.Path = path
			} else {
				// Add sub-entry if not existant
				if newemo.Sub == nil {
					newemo.Sub = make(Table)
				}
			}
			(*curtab)[cprune] = newemo
			curtab = &newemo.Sub
		}
		return nil
	})
	return tab, err
}