package markdown

import (
	"strings"

	"github.com/alecthomas/chroma/v2"
	"github.com/alecthomas/chroma/v2/styles"
)

var chromaToHljs = map[chroma.TokenType]string{
	chroma.Keyword:            "hljs-keyword",
	chroma.KeywordConstant:    "hljs-keyword",
	chroma.KeywordDeclaration: "hljs-keyword",
	chroma.KeywordNamespace:   "hljs-keyword",
	chroma.KeywordPseudo:      "hljs-keyword",
	chroma.KeywordReserved:    "hljs-keyword",
	chroma.KeywordType:        "hljs-type",

	chroma.Name:              "hljs-variable",
	chroma.NameBuiltin:       "hljs-built_in",
	chroma.NameBuiltinPseudo: "hljs-built_in",
	chroma.NameClass:         "hljs-title class_",
	chroma.NameConstant:      "hljs-variable constant_",
	chroma.NameDecorator:     "hljs-meta",
	chroma.NameEntity:        "hljs-name",
	chroma.NameException:     "hljs-title class_",
	chroma.NameFunction:      "hljs-title function_",
	chroma.NameFunctionMagic: "hljs-title function_",
	chroma.NameLabel:         "hljs-symbol",
	chroma.NameNamespace:     "hljs-title class_",
	chroma.NameOther:         "hljs-variable",
	chroma.NameProperty:      "hljs-property",
	chroma.NameTag:           "hljs-tag",
	chroma.NameVariable:      "hljs-variable",
	chroma.NameVariableClass: "hljs-variable",
	chroma.NameVariableGlobal: "hljs-variable",
	chroma.NameVariableInstance: "hljs-variable",
	chroma.NameVariableMagic: "hljs-variable",
	chroma.NameAttribute:     "hljs-attr",

	chroma.Literal:     "hljs-literal",
	chroma.LiteralDate: "hljs-number",

	chroma.String:          "hljs-string",
	chroma.StringAffix:     "hljs-string",
	chroma.StringBacktick:  "hljs-string",
	chroma.StringChar:      "hljs-string",
	chroma.StringDelimiter: "hljs-string",
	chroma.StringDoc:       "hljs-string",
	chroma.StringDouble:    "hljs-string",
	chroma.StringEscape:    "hljs-char escape_",
	chroma.StringHeredoc:   "hljs-string",
	chroma.StringInterpol:  "hljs-subst",
	chroma.StringOther:     "hljs-string",
	chroma.StringRegex:     "hljs-regexp",
	chroma.StringSingle:    "hljs-string",
	chroma.StringSymbol:    "hljs-symbol",

	chroma.Number:            "hljs-number",
	chroma.NumberBin:         "hljs-number",
	chroma.NumberFloat:       "hljs-number",
	chroma.NumberHex:         "hljs-number",
	chroma.NumberInteger:     "hljs-number",
	chroma.NumberIntegerLong: "hljs-number",
	chroma.NumberOct:         "hljs-number",

	chroma.Operator:     "hljs-operator",
	chroma.OperatorWord: "hljs-keyword",

	chroma.Punctuation: "hljs-punctuation",

	chroma.Comment:            "hljs-comment",
	chroma.CommentHashbang:    "hljs-meta",
	chroma.CommentMultiline:   "hljs-comment",
	chroma.CommentPreproc:     "hljs-meta",
	chroma.CommentPreprocFile: "hljs-meta",
	chroma.CommentSingle:      "hljs-comment",
	chroma.CommentSpecial:     "hljs-doctag",

	chroma.Generic:           "hljs-code",
	chroma.GenericDeleted:    "hljs-deletion",
	chroma.GenericEmph:       "hljs-emphasis",
	chroma.GenericError:      "hljs-strong",
	chroma.GenericHeading:    "hljs-section",
	chroma.GenericInserted:   "hljs-addition",
	chroma.GenericOutput:     "hljs-code",
	chroma.GenericPrompt:     "hljs-meta prompt_",
	chroma.GenericStrong:     "hljs-strong",
	chroma.GenericSubheading: "hljs-section",
	chroma.GenericTraceback:  "hljs-code",
	chroma.GenericUnderline:  "hljs-code",

	chroma.Text:            "",
	chroma.TextWhitespace:  "",
}

func GenerateHljsCSS(themeName string) (string, error) {
	style := styles.Get(themeName)
	if style == nil {
		style = styles.Get("github")
	}

	var css strings.Builder
	css.WriteString("/* Auto-generated from Chroma theme: " + themeName + " */\n")

	bg := style.Get(chroma.Background)
	if bg.Background.IsSet() {
		css.WriteString(".prose pre { background: " + bg.Background.String() + "; }\n")
	}
	if bg.Colour.IsSet() {
		css.WriteString(".prose pre code { color: " + bg.Colour.String() + "; }\n")
	}

	seen := make(map[string]bool)

	for chromaToken, hljsClass := range chromaToHljs {
		if hljsClass == "" {
			continue
		}

		entry := style.Get(chromaToken)
		if !entry.Colour.IsSet() && entry.Bold != chroma.Yes && entry.Italic != chroma.Yes {
			continue
		}

		if seen[hljsClass] {
			continue
		}
		seen[hljsClass] = true

		selector := "." + strings.ReplaceAll(hljsClass, " ", ".")
		css.WriteString(selector + " {")

		if entry.Colour.IsSet() {
			css.WriteString(" color: " + entry.Colour.String() + ";")
		}
		if entry.Bold == chroma.Yes {
			css.WriteString(" font-weight: bold;")
		}
		if entry.Italic == chroma.Yes {
			css.WriteString(" font-style: italic;")
		}

		css.WriteString(" }\n")
	}

	return css.String(), nil
}

func ListThemes() []string {
	return styles.Names()
}