package svg

import (
	"fmt"
	"io"
	"strings"

	"github.com/alecthomas/chroma"
)

// Option sets an option of the SVG formatter.
type Option func(f *Formatter)

// New SVG formatter.
func New(options ...Option) *Formatter {
	f := &Formatter{}
	for _, option := range options {
		option(f)
	}
	return f
}

// Formatter that generates SVG.
type Formatter struct {
}

func (f *Formatter) Format(w io.Writer, style *chroma.Style, iterator chroma.Iterator) (err error) {
	defer func() {
		if perr := recover(); perr != nil {
			err = perr.(error)
		}
	}()
	f.writeSVG(w, style, iterator.Tokens())
	return err
}

var svgEscaper = strings.NewReplacer(
	`&`, "&",
	`<`, "&lt;",
	`>`, "&gt;",
	`"`, "&quot;",
	` `, "&#160;",
	`	`, "&#160;&#160;&#160;&#160;",
)

// EscapeString escapes special characters.
func escapeString(s string) string {
	return svgEscaper.Replace(s)
}

func (f *Formatter) writeSVG(w io.Writer, style *chroma.Style, tokens []chroma.Token) { // nolint: gocyclo
	svgStyles := f.styleToSVG(style)
	lines := chroma.SplitTokensIntoLines(tokens)

	fmt.Fprint(w, "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n")
	fmt.Fprint(w, "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.0//EN\" \"http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd\">\n")
	fmt.Fprintf(w, "<svg height=\"%d\" xmlns=\"http://www.w3.org/2000/svg\">\n", len(lines)*22)
	fmt.Fprintf(w, "<rect width=\"100%%\" height=\"100%%\" fill=\"%s\"/>\n", style.Get(chroma.Background).Background.String())
	fmt.Fprintf(w, "<g font-family=\"Consolas, Monaco, Lucida Console, Liberation Mono, DejaVu Sans Mono, Bitstream Vera Sans Mono, Courier New, monospace\" font-size=\"14px\" fill=\"%s\">\n", style.Get(chroma.Text).Colour.String())

	f.writeTokenBackgrounds(w, lines, style)

	for index, tokens := range lines {
		fmt.Fprintf(w, "<text x=\"0\" y=\"%d\" xml:space=\"preserve\">", (14+7)*(index+1))

		for _, token := range tokens {
			text := escapeString(token.String())
			attr := f.styleAttr(svgStyles, token.Type)
			if attr != "" {
				text = fmt.Sprintf("<tspan %s>%s</tspan>", attr, text)
			}
			fmt.Fprint(w, text)
		}
		fmt.Fprint(w, "</text>")
	}

	fmt.Fprint(w, "\n</g>\n")
	fmt.Fprint(w, "</svg>\n")
}

// There is no background attribute for text in SVG so simply calculate the position and text
// of tokens with a background color that differs from the default and add a rectangle for each before
// adding the token.
func (f *Formatter) writeTokenBackgrounds(w io.Writer, lines [][]chroma.Token, style *chroma.Style) {
	for index, tokens := range lines {
		lineLength := 0
		for _, token := range tokens {
			length := len(strings.Replace(token.String(), `	`, "    ", -1))
			tokenBackground := style.Get(token.Type).Background
			if tokenBackground.IsSet() && tokenBackground != style.Get(chroma.Background).Background {
				fmt.Fprintf(w, "<rect id=\"%s\" x=\"%d\" y=\"%d\" width=\"%d\" height=\"%d\" fill=\"%s\" />\n", escapeString(token.String()), lineLength*8, (14+7)*index+7, length*8, 14, style.Get(token.Type).Background.String())
			}
			lineLength += length
		}
	}
}

func (f *Formatter) styleAttr(styles map[chroma.TokenType]string, tt chroma.TokenType) string {
	if _, ok := styles[tt]; !ok {
		tt = tt.SubCategory()
		if _, ok := styles[tt]; !ok {
			tt = tt.Category()
			if _, ok := styles[tt]; !ok {
				return ""
			}
		}
	}
	return styles[tt]
}

func (f *Formatter) styleToSVG(style *chroma.Style) map[chroma.TokenType]string {
	converted := map[chroma.TokenType]string{}
	bg := style.Get(chroma.Background)
	// Convert the style.
	for t := range chroma.StandardTypes {
		entry := style.Get(t)
		if t != chroma.Background {
			entry = entry.Sub(bg)
		}
		if entry.IsZero() {
			continue
		}
		converted[t] = StyleEntryToSVG(entry)
	}
	return converted
}

// StyleEntryToSVG converts a chroma.StyleEntry to SVG attributes.
func StyleEntryToSVG(e chroma.StyleEntry) string {
	var styles []string

	if e.Colour.IsSet() {
		styles = append(styles, "fill=\""+e.Colour.String()+"\"")
	}
	if e.Bold == chroma.Yes {
		styles = append(styles, "font-weight=\"bold\"")
	}
	if e.Italic == chroma.Yes {
		styles = append(styles, "font-style=\"italic\"")
	}
	if e.Underline == chroma.Yes {
		styles = append(styles, "text-decoration=\"underline\"")
	}
	return strings.Join(styles, " ")
}