package utils

import (
	"regexp"
	"strings"
)

// Helper function to change patterns
func changeAll(text, oldIns, newIns, leftDelim, rightDelim, newLeftDelim, newRightDelim string) string {
	pattern := regexp.MustCompile(regexp.QuoteMeta(oldIns) + `\s*` + regexp.QuoteMeta(leftDelim) + `(.*?)` + regexp.QuoteMeta(rightDelim))
	return pattern.ReplaceAllString(text, newIns+newLeftDelim+"$1"+newRightDelim)
}

// Helper function to remove dollar surroundings
func rmDollarSurr(text string) string {
	if strings.HasPrefix(text, "$") && strings.HasSuffix(text, "$") {
		return text[1 : len(text)-1]
	}
	return text
}

// ToKatex converts LaTeX formula to KaTeX compatible format
func ToKatex(formula string) string {
	res := formula

	// Remove mbox surrounding
	res = changeAll(res, `\mbox `, " ", "{", "}", "", "")
	res = changeAll(res, `\mbox`, " ", "{", "}", "", "")

	// Remove hbox surrounding
	hboxPattern := regexp.MustCompile(`\\hbox to ?-? ?\d+\.\d+(pt)?\{`)
	res = hboxPattern.ReplaceAllString(res, `\hbox{`)
	res = changeAll(res, `\hbox`, " ", "{", "}", "", " ")

	// Remove raise surrounding
	raisePattern := regexp.MustCompile(`\\raise ?-? ?\d+\.\d+(pt)?`)
	res = raisePattern.ReplaceAllString(res, " ")

	// Remove makebox
	makeboxPattern := regexp.MustCompile(`\\makebox ?\[\d+\.\d+(pt)?\]\{`)
	res = makeboxPattern.ReplaceAllString(res, `\makebox{`)
	res = changeAll(res, `\makebox`, " ", "{", "}", "", " ")

	// Remove vbox, scalebox, raisebox surrounding
	raisebox := regexp.MustCompile(`\\raisebox\{-? ?\d+\.\d+(pt)?\}\{`)
	scalebox := regexp.MustCompile(`\\scalebox\{-? ?\d+\.\d+(pt)?\}\{`)
	res = raisebox.ReplaceAllString(res, `\raisebox{`)
	res = scalebox.ReplaceAllString(res, `\scalebox{`)
	res = changeAll(res, `\scalebox`, " ", "{", "}", "", " ")
	res = changeAll(res, `\raisebox`, " ", "{", "}", "", " ")
	res = changeAll(res, `\vbox`, " ", "{", "}", "", " ")

	// Handle size instructions
	sizeInstructions := []string{
		`\Huge`, `\huge`, `\LARGE`, `\Large`, `\large`,
		`\normalsize`, `\small`, `\footnotesize`, `\tiny`,
	}
	for _, ins := range sizeInstructions {
		res = changeAll(res, ins, ins, "$", "$", "{", "}")
	}

	// Handle boldmath
	res = changeAll(res, `\boldmath `, `\bm`, "{", "}", "{", "}")
	res = changeAll(res, `\boldmath`, `\bm`, "{", "}", "{", "}")
	res = changeAll(res, `\boldmath `, `\bm`, "$", "$", "{", "}")
	res = changeAll(res, `\boldmath`, `\bm`, "$", "$", "{", "}")

	// Handle other instructions
	res = changeAll(res, `\scriptsize`, `\scriptsize`, "$", "$", "{", "}")
	res = changeAll(res, `\emph`, `\textit`, "{", "}", "{", "}")
	res = changeAll(res, `\emph `, `\textit`, "{", "}", "{", "}")

	// Handle math delimiters
	delimiters := []string{
		`\left`, `\middle`, `\right`, `\big`, `\Big`, `\bigg`, `\Bigg`,
		`\bigl`, `\Bigl`, `\biggl`, `\Biggl`, `\bigm`, `\Bigm`, `\biggm`,
		`\Biggm`, `\bigr`, `\Bigr`, `\biggr`, `\Biggr`,
	}
	for _, delim := range delimiters {
		res = changeAll(res, delim, delim, "{", "}", "", "")
	}

	// Handle display math
	displayMath := regexp.MustCompile(`\\\[(.*?)\\\]`)
	res = displayMath.ReplaceAllString(res, "$1\\newline")

	res = strings.TrimSuffix(res, `\newline`)

	// Remove multiple spaces
	spaces := regexp.MustCompile(`(\\,){1,}`)
	res = spaces.ReplaceAllString(res, " ")
	res = regexp.MustCompile(`(\\!){1,}`).ReplaceAllString(res, " ")
	res = regexp.MustCompile(`(\\;){1,}`).ReplaceAllString(res, " ")
	res = regexp.MustCompile(`(\\:){1,}`).ReplaceAllString(res, " ")
	res = regexp.MustCompile(`\\vspace\{.*?}`).ReplaceAllString(res, "")

	// Merge consecutive text
	textPattern := regexp.MustCompile(`(\\text\{[^}]*\}\s*){2,}`)
	res = textPattern.ReplaceAllStringFunc(res, func(match string) string {
		texts := regexp.MustCompile(`\\text\{([^}]*)\}`).FindAllStringSubmatch(match, -1)
		var merged strings.Builder
		for _, t := range texts {
			merged.WriteString(t[1])
		}
		return `\text{` + merged.String() + "}"
	})

	res = strings.ReplaceAll(res, `\bf `, "")
	res = rmDollarSurr(res)

	// Remove extra spaces
	res = regexp.MustCompile(` +`).ReplaceAllString(res, " ")

	return strings.TrimSpace(res)
}