package format

import (
	"strings"
)

// ANSI color codes.
const (
	reset   = "\033[0m"
	red     = "\033[31m"
	green   = "\033[32m"
	yellow  = "\033[33m"
	blue    = "\033[34m"
	magenta = "\033[35m"
	cyan    = "\033[36m"
	gray    = "\033[90m"
)

// Colorize applies syntax highlighting to formatted Confluence XML.
func Colorize(input string) string {
	var buf strings.Builder
	i := 0
	for i < len(input) {
		if input[i] != '<' {
			// Text content — no color
			end := strings.Index(input[i:], "<")
			if end == -1 {
				buf.WriteString(input[i:])
				break
			}
			buf.WriteString(input[i : i+end])
			i += end
			continue
		}

		// CDATA
		if strings.HasPrefix(input[i:], "<![CDATA[") {
			end := strings.Index(input[i:], "]]>")
			if end == -1 {
				buf.WriteString(gray)
				buf.WriteString(input[i:])
				buf.WriteString(reset)
				break
			}
			buf.WriteString(gray)
			buf.WriteString(input[i : i+end+3])
			buf.WriteString(reset)
			i += end + 3
			continue
		}

		// Comment
		if strings.HasPrefix(input[i:], "<!--") {
			end := strings.Index(input[i:], "-->")
			if end == -1 {
				buf.WriteString(gray)
				buf.WriteString(input[i:])
				buf.WriteString(reset)
				break
			}
			buf.WriteString(gray)
			buf.WriteString(input[i : i+end+3])
			buf.WriteString(reset)
			i += end + 3
			continue
		}

		// XML tag
		end := strings.Index(input[i:], ">")
		if end == -1 {
			buf.WriteString(input[i:])
			break
		}
		tag := input[i : i+end+1]
		buf.WriteString(colorizeTag(tag))
		i += end + 1
	}
	return buf.String()
}

func colorizeTag(tag string) string {
	var buf strings.Builder

	// Closing tag: </name>
	if strings.HasPrefix(tag, "</") {
		name := tag[2 : len(tag)-1]
		buf.WriteString(gray)
		buf.WriteString("</")
		buf.WriteString(reset)
		buf.WriteString(tagNameColor(name))
		buf.WriteString(name)
		buf.WriteString(reset)
		buf.WriteString(gray)
		buf.WriteString(">")
		buf.WriteString(reset)
		return buf.String()
	}

	// Opening or self-closing tag
	selfClosing := strings.HasSuffix(tag, "/>")
	inner := tag[1:]
	if selfClosing {
		inner = inner[:len(inner)-2]
	} else {
		inner = inner[:len(inner)-1]
	}

	// Split tag name from attributes
	nameEnd := strings.IndexAny(inner, " \t\n")
	var name, attrs string
	if nameEnd == -1 {
		name = inner
	} else {
		name = inner[:nameEnd]
		attrs = inner[nameEnd:]
	}

	buf.WriteString(gray)
	buf.WriteString("<")
	buf.WriteString(reset)
	buf.WriteString(tagNameColor(name))
	buf.WriteString(name)
	buf.WriteString(reset)

	if attrs != "" {
		buf.WriteString(colorizeAttrs(attrs))
	}

	if selfClosing {
		buf.WriteString(gray)
		buf.WriteString("/>")
		buf.WriteString(reset)
	} else {
		buf.WriteString(gray)
		buf.WriteString(">")
		buf.WriteString(reset)
	}

	return buf.String()
}

func tagNameColor(name string) string {
	lower := strings.ToLower(name)
	switch {
	case strings.HasPrefix(lower, "ac:"):
		return magenta
	case strings.HasPrefix(lower, "ri:"):
		return cyan
	default:
		return blue
	}
}

func colorizeAttrs(attrs string) string {
	var buf strings.Builder
	rest := attrs
	for len(rest) > 0 {
		// Find next attribute: name="value" or name='value'
		eqIdx := strings.Index(rest, "=")
		if eqIdx == -1 {
			// No more attributes, just whitespace or text
			buf.WriteString(rest)
			break
		}

		// Everything before = is whitespace + attr name
		before := rest[:eqIdx]
		rest = rest[eqIdx+1:]

		// Split leading whitespace from attr name
		trimmed := strings.TrimLeft(before, " \t\n")
		ws := before[:len(before)-len(trimmed)]

		buf.WriteString(ws)
		buf.WriteString(yellow)
		buf.WriteString(trimmed)
		buf.WriteString(reset)
		buf.WriteString(gray)
		buf.WriteString("=")
		buf.WriteString(reset)

		// Read quoted value
		if len(rest) > 0 && (rest[0] == '"' || rest[0] == '\'') {
			quote := rest[0]
			endQ := strings.IndexByte(rest[1:], quote)
			if endQ == -1 {
				buf.WriteString(green)
				buf.WriteString(rest)
				buf.WriteString(reset)
				break
			}
			buf.WriteString(green)
			buf.WriteString(rest[:endQ+2])
			buf.WriteString(reset)
			rest = rest[endQ+2:]
		}
	}
	return buf.String()
}