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

// Additional string functions: RAT, STRZERO, DESCEND, HB_VALTOSTR,
// MEMOREAD, MEMOWRIT, MEMOTRAN

package hbrtl

import (
	"five/hbrt"
	"fmt"
	"os"
	"strings"
)

// RAT(cSearch, cTarget [, nOccurrence]) → nPos
// Returns position of LAST occurrence of cSearch in cTarget.
func Rat(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	search := t.Local(1).AsString()
	target := t.Local(2).AsString()

	if search == "" || target == "" {
		t.RetInt(0)
		return
	}

	nOccurrence := 1
	if nParams >= 3 && !t.Local(3).IsNil() {
		nOccurrence = t.Local(3).AsInt()
		if nOccurrence < 1 {
			nOccurrence = 1
		}
	}

	// Find nth occurrence from the right
	pos := -1
	from := len(target)
	for i := 0; i < nOccurrence; i++ {
		pos = strings.LastIndex(target[:from], search)
		if pos < 0 {
			t.RetInt(0)
			return
		}
		from = pos
	}
	t.RetInt(int64(pos + 1)) // 1-based
}

// STRZERO(nValue, nLen [, nDec]) → cString
// Converts number to string padded with leading zeros.
func StrZero(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	val := t.Local(1)
	nLen := 10
	nDec := 0

	if nParams >= 2 && !t.Local(2).IsNil() {
		nLen = t.Local(2).AsInt()
	}
	if nParams >= 3 && !t.Local(3).IsNil() {
		nDec = t.Local(3).AsInt()
	}

	var s string
	if nDec > 0 {
		fmtStr := fmt.Sprintf("%%0%d.%df", nLen, nDec)
		s = fmt.Sprintf(fmtStr, val.AsNumDouble())
	} else {
		fmtStr := fmt.Sprintf("%%0%dd", nLen)
		s = fmt.Sprintf(fmtStr, val.AsLong())
	}

	// Ensure exact length
	if len(s) > nLen {
		s = strings.Repeat("*", nLen)
	}
	t.RetString(s)
}

// DESCEND(xValue) → xDescended
// For strings: flips each byte (255-byte). For numbers: negates. For dates: max-date.
func Descend(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	v := t.Local(1)
	switch {
	case v.IsString():
		s := v.AsString()
		buf := make([]byte, len(s))
		for i := 0; i < len(s); i++ {
			buf[i] = 255 - s[i]
		}
		t.RetString(string(buf))
	case v.IsNumeric():
		t.RetVal(hbrt.MakeNumInt(-v.AsLong()))
	case v.IsDate():
		// Max Julian (2^24) minus date
		t.RetVal(hbrt.MakeNumInt(5373484 - v.AsJulian()))
	default:
		t.RetNil()
	}
}

// HB_VALTOSTR(xValue) → cString
// Converts any value to its string representation.
func HbValToStr(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	t.RetString(valueToDisplay(t.Local(1)))
}

// HB_CSTR(xVal) → cString — converts any value to string representation
func HbCStr(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	t.RetString(valueToDisplay(t.Local(1)))
}

// HB_NTOS(nVal) → cString — converts numeric to string without leading spaces
func HbNtos(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsNumInt() {
		t.RetString(fmt.Sprintf("%d", v.AsNumInt()))
	} else if v.IsNumeric() {
		t.RetString(fmt.Sprintf("%g", v.AsNumDouble()))
	} else {
		t.RetString("0")
	}
}

// HB_VALTOEXP(xVal) → cExpr — returns Harbour expression representation
func HbValToExp(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	switch {
	case v.IsNil():
		t.RetString("NIL")
	case v.IsString():
		t.RetString(`"` + v.AsString() + `"`)
	case v.IsNumInt():
		t.RetString(fmt.Sprintf("%d", v.AsNumInt()))
	case v.IsNumeric():
		t.RetString(fmt.Sprintf("%g", v.AsNumDouble()))
	case v.IsLogical():
		if v.AsBool() {
			t.RetString(".T.")
		} else {
			t.RetString(".F.")
		}
	case v.IsDate():
		t.RetString(fmt.Sprintf("0d%08d", v.AsJulian()))
	default:
		t.RetString(valueToDisplay(v))
	}
}

// MEMOREAD(cFileName) → cContents
// Reads entire file into a string.
func MemoRead(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	fname := t.Local(1).AsString()
	data, err := os.ReadFile(fname)
	if err != nil {
		t.RetString("")
		return
	}
	t.RetString(string(data))
}

// MEMOWRIT(cFileName, cString [, lAddEOF]) → lSuccess
// Writes string to file.
func MemoWrit(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()
	fname := t.Local(1).AsString()
	content := t.Local(2).AsString()
	err := os.WriteFile(fname, []byte(content), 0644)
	t.RetBool(err == nil)
}

// MEMOTRAN(cMemoText [, cSoftCR [, cHardCR]]) → cString
// Replaces soft/hard CR in memo fields.
func MemoTran(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	text := t.Local(1).AsString()
	softCR := ";"
	hardCR := ";"
	if nParams >= 2 && !t.Local(2).IsNil() {
		softCR = t.Local(2).AsString()
	}
	if nParams >= 3 && !t.Local(3).IsNil() {
		hardCR = t.Local(3).AsString()
	}

	// Replace soft CR (141+10) then hard CR (13+10)
	text = strings.ReplaceAll(text, "\x8d\n", softCR)
	text = strings.ReplaceAll(text, "\r\n", hardCR)
	t.RetString(text)
}