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

// String functions for the Five runtime library.
// Implements Harbour-compatible string functions.
package hbrtl

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

// Str converts a numeric value to a string.
// Harbour: Str(nValue [, nWidth [, nDec]]) → cString
func Str(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	v := t.Local(1)
	if !v.IsNumeric() {
		t.PushString("")
		t.RetValue()
		return
	}

	d := v.AsNumDouble()

	// Width and decimals: use caller's args if provided, else Value metadata
	width := int(v.Length())
	dec := int(v.Decimal())

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

	if width == 0 || width == 255 {
		width = 10 // default width
	}
	if dec == 255 {
		dec = 0
	}

	s := fmt.Sprintf("%*.*f", width, dec, d)
	// Harbour pads with spaces if shorter
	if len(s) < width {
		s = strings.Repeat(" ", width-len(s)) + s
	}
	// Harbour returns asterisks if wider than width
	if len(s) > width && width > 0 {
		s = strings.Repeat("*", width)
	}

	t.PushString(s)
	t.RetValue()
}

// Val converts a string to a numeric value.
// Harbour: Val(cString) → nValue
func Val(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	v := t.Local(1)
	if !v.IsString() {
		t.RetInt(0)
		return
	}

	s := strings.TrimSpace(v.AsString())
	if s == "" {
		t.RetInt(0)
		return
	}

	// Try integer first
	var n int64
	if _, err := fmt.Sscanf(s, "%d", &n); err == nil {
		// Check if there's a decimal point
		if !strings.Contains(s, ".") {
			t.RetInt(n)
			return
		}
	}

	// Try float
	var f float64
	if _, err := fmt.Sscanf(s, "%f", &f); err == nil {
		// Count decimal places
		dec := 0
		if idx := strings.Index(s, "."); idx >= 0 {
			dec = len(s) - idx - 1
		}
		t.PushValue(hbrt.MakeDouble(f, uint16(len(s)), uint16(dec)))
		t.RetValue()
		return
	}

	t.RetInt(0)
}

// Len returns the length of a string or array.
// Harbour: Len(xValue) → nLen
func Len(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()

	v := t.Local(1)
	switch {
	case v.IsString():
		t.RetInt(int64(v.StringLen()))
	case v.IsArray():
		t.RetInt(int64(len(v.AsArray().Items)))
	case v.IsHash():
		t.RetInt(int64(len(v.AsHash().Keys)))
	default:
		t.RetInt(0)
	}
}

// SubStr extracts a substring.
// Harbour: SubStr(cString, nStart [, nLen]) → cString
func SubStr(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	v := t.Local(1)
	if !v.IsString() {
		t.PushString("")
		t.RetValue()
		return
	}

	s := v.AsString()
	start := int(t.Local(2).AsNumInt())

	// Harbour: 1-based index, negative = from end
	if start < 0 {
		start = len(s) + start + 1
	}
	if start < 1 {
		start = 1
	}
	start-- // convert to 0-based

	if start >= len(s) {
		t.PushString("")
		t.RetValue()
		return
	}

	result := s[start:]

	// Optional 3rd param: length
	if nParams >= 3 && !t.Local(3).IsNil() {
		nLen := int(t.Local(3).AsNumInt())
		if nLen < 0 {
			nLen = 0
		}
		if nLen < len(result) {
			result = result[:nLen]
		}
	}

	t.PushString(result)
	t.RetValue()
}

// Upper converts string to uppercase.
// Harbour: Upper(cString) → cString
func Upper(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsString() {
		t.PushString(strings.ToUpper(v.AsString()))
	} else {
		t.PushString("")
	}
	t.RetValue()
}

// Lower converts string to lowercase.
func Lower(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsString() {
		t.PushString(strings.ToLower(v.AsString()))
	} else {
		t.PushString("")
	}
	t.RetValue()
}

// AllTrim removes leading and trailing spaces.
func AllTrim(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsString() {
		t.PushString(strings.TrimSpace(v.AsString()))
	} else {
		t.PushString("")
	}
	t.RetValue()
}

// LTrim trims leading spaces only. Harbour: LTRIM(cString) → cString
func LTrim(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsString() {
		t.PushString(strings.TrimLeft(v.AsString(), " "))
	} else {
		t.PushString("")
	}
	t.RetValue()
}

// RTrim trims trailing spaces only. Harbour: RTRIM(cString) / TRIM(cString)
func RTrim(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsString() {
		t.PushString(strings.TrimRight(v.AsString(), " "))
	} else {
		t.PushString("")
	}
	t.RetValue()
}

// Space returns a string of n spaces.
// Harbour: Space(nCount) → cString
func Space(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	n := t.Local(1).AsNumInt()
	if n < 0 {
		n = 0
	}
	t.PushString(strings.Repeat(" ", int(n)))
	t.RetValue()
}

// PadR pads a string on the right to a specified length.
func PadR(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	s := valueToDisplay(t.Local(1))
	n := int(t.Local(2).AsNumInt())
	if len(s) >= n {
		t.PushString(s[:n])
	} else {
		t.PushString(s + strings.Repeat(" ", n-len(s)))
	}
	t.RetValue()
}

// PadL pads a string on the left to a specified length.
func PadL(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	s := valueToDisplay(t.Local(1))
	n := int(t.Local(2).AsNumInt())
	if len(s) >= n {
		t.PushString(s[len(s)-n:])
	} else {
		t.PushString(strings.Repeat(" ", n-len(s)) + s)
	}
	t.RetValue()
}

// Replicate repeats a string n times.
func Replicate(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	s := t.Local(1).AsString()
	n := int(t.Local(2).AsNumInt())
	if n < 0 {
		n = 0
	}
	t.PushString(strings.Repeat(s, n))
	t.RetValue()
}

// --- Utility functions ---

// ValType returns a single character indicating the value type.
// Harbour: ValType(xValue) → cType
func ValType(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	var c string
	switch {
	case v.IsNil():
		c = "U"
	case v.IsLogical():
		c = "L"
	case v.IsNumeric():
		c = "N"
	case v.IsString():
		c = "C"
	case v.IsDate(), v.IsTimestamp():
		c = "D"
	case v.IsArray():
		c = "A"
	case v.IsHash():
		c = "H"
	case v.IsBlock():
		c = "B"
	case v.IsObject():
		c = "O"
	case v.IsPointer():
		c = "P"
	case v.IsSymbol():
		c = "S"
	default:
		c = "U"
	}
	t.PushString(c)
	t.RetValue()
}

// Empty checks if a value is "empty".
// Harbour: Empty(xValue) → lEmpty
func Empty(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	var empty bool
	switch {
	case v.IsNil():
		empty = true
	case v.IsLogical():
		empty = !v.AsBool()
	case v.IsNumeric():
		empty = v.AsNumDouble() == 0
	case v.IsString():
		empty = strings.TrimSpace(v.AsString()) == ""
	case v.IsDate():
		empty = v.AsJulian() == 0
	case v.IsArray():
		empty = len(v.AsArray().Items) == 0
	case v.IsHash():
		empty = len(v.AsHash().Keys) == 0
	case v.IsBlock():
		empty = false
	default:
		empty = true
	}
	t.PushValue(hbrt.MakeBool(empty))
	t.RetValue()
}

// Abs returns the absolute value.
func Abs(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsNumInt() {
		n := v.AsNumInt()
		if n < 0 {
			n = -n
		}
		t.PushValue(hbrt.MakeNumInt(n))
	} else if v.IsDouble() {
		t.PushValue(hbrt.MakeDouble(math.Abs(v.AsDouble()), v.Length(), v.Decimal()))
	} else {
		t.RetInt(0)
		return
	}
	t.RetValue()
}

// Int returns the integer part of a numeric value.
func Int(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	v := t.Local(1)
	if v.IsNumInt() {
		t.PushValue(v)
	} else if v.IsDouble() {
		t.PushValue(hbrt.MakeLong(int64(v.AsDouble())))
	} else {
		t.PushValue(hbrt.MakeInt(0))
	}
	t.RetValue()
}