// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// Regular expression functions using Go's regexp package.
// HB_REGEXCOMP, HB_REGEXMATCH, HB_REGEXSPLIT, HB_REGEXALL, HB_REGEXREPLACE

package hbrtl

import (
	"five/hbrt"
	"regexp"
)

// HB_REGEXCOMP(cPattern [, lCaseSensitive]) → pRegex
// Returns compiled regex as a pointer value.
func HbRegexComp(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	pattern := t.Local(1).AsString()

	// Default case-sensitive; if 2nd param is .F., add (?i) prefix
	if nParams >= 2 && !t.Local(2).IsNil() && !t.Local(2).AsBool() {
		pattern = "(?i)" + pattern
	}

	re, err := regexp.Compile(pattern)
	if err != nil {
		t.RetNil()
		return
	}
	t.RetPointer(re)
}

// HB_REGEXMATCH(cPattern|pRegex, cString [, lCaseSensitive]) → lMatch
func HbRegexMatch(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	re := getRegex(t, 1, nParams >= 3)
	if re == nil {
		t.RetBool(false)
		return
	}

	str := t.Local(2).AsString()
	t.RetBool(re.MatchString(str))
}

// HB_REGEXSPLIT(cPattern|pRegex, cString [, lCaseSensitive]) → aResult
func HbRegexSplit(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	re := getRegex(t, 1, nParams >= 3)
	if re == nil {
		t.RetNil()
		return
	}

	str := t.Local(2).AsString()
	parts := re.Split(str, -1)

	items := make([]hbrt.Value, len(parts))
	for i, p := range parts {
		items[i] = hbrt.MakeString(p)
	}
	t.RetVal(hbrt.MakeArrayFrom(items))
}

// HB_REGEXALL(cPattern|pRegex, cString [, lCaseSensitive]) → aMatches
func HbRegexAll(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	re := getRegex(t, 1, nParams >= 3)
	if re == nil {
		t.RetNil()
		return
	}

	str := t.Local(2).AsString()
	matches := re.FindAllString(str, -1)

	items := make([]hbrt.Value, len(matches))
	for i, m := range matches {
		items[i] = hbrt.MakeString(m)
	}
	t.RetVal(hbrt.MakeArrayFrom(items))
}

// HB_REGEXREPLACE(cPattern|pRegex, cString, cReplace [, lCaseSensitive]) → cResult
func HbRegexReplace(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	re := getRegex(t, 1, nParams >= 4)
	if re == nil {
		t.RetString("")
		return
	}

	str := t.Local(2).AsString()
	repl := t.Local(3).AsString()
	t.RetString(re.ReplaceAllString(str, repl))
}

// getRegex extracts or compiles a regex from param at given index.
func getRegex(t *hbrt.Thread, paramIdx int, hasCaseParam bool) *regexp.Regexp {
	v := t.Local(paramIdx)
	if v.IsPointer() {
		if re, ok := v.AsPointer().(*regexp.Regexp); ok {
			return re
		}
	}
	// String pattern — compile on the fly
	pattern := v.AsString()
	if hasCaseParam {
		caseParam := t.Local(paramIdx + 2) // 3rd or 4th param
		if !caseParam.IsNil() && !caseParam.AsBool() {
			pattern = "(?i)" + pattern
		}
	}
	re, err := regexp.Compile(pattern)
	if err != nil {
		return nil
	}
	return re
}