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

// valuemethods.go — Built-in methods on basic Value types.
//
// Enables method-style calls on strings, arrays, numbers, hashes:
//   cStr:Upper()          → strings.ToUpper
//   aArr:Sort()           → sort + return
//   nVal:Round(2)         → Round(n, dec)
//   hHash:Keys()          → key array
//
// Key feature: CHAINING
//   cStr:Trim():Upper():Left(5)
//
// Implementation: Thread.SendBuiltin() is called before class dispatch.
// If the value is not an object but has a matching built-in method,
// execute it and return true. Otherwise fall through to class Send.

package hbrt

import (
	"fmt"
	"math"
	"sort"
	"strings"
)

// ValueMethod is a built-in method on a basic type.
type ValueMethod func(t *Thread, self Value, args []Value) Value

// builtinMethods maps "TYPE:METHOD" → implementation.
var builtinMethods = map[string]ValueMethod{
	// --- String methods ---
	"S:UPPER":     vmStrUpper,
	"S:LOWER":     vmStrLower,
	"S:TRIM":      vmStrTrim,
	"S:LTRIM":     vmStrLTrim,
	"S:RTRIM":     vmStrRTrim,
	"S:LEFT":      vmStrLeft,
	"S:RIGHT":     vmStrRight,
	"S:SUBSTR":    vmStrSubstr,
	"S:LEN":       vmStrLen,
	"S:REPLACE":   vmStrReplace,
	"S:SPLIT":     vmStrSplit,
	"S:CONTAINS":  vmStrContains,
	"S:STARTS":    vmStrStarts,
	"S:ENDS":      vmStrEnds,
	"S:REVERSE":   vmStrReverse,
	"S:REPLICATE": vmStrReplicate,
	"S:COPY":      vmStrCopy,
	"S:AT":        vmStrAt,
	"S:EMPTY":     vmStrEmpty,
	"S:VAL":       vmStrVal,

	// --- Array methods ---
	"A:LEN":    vmArrLen,
	"A:PUSH":   vmArrPush,
	"A:POP":    vmArrPop,
	"A:SORT":   vmArrSort,
	"A:FIND":   vmArrFind,
	"A:MAP":    vmArrMap,
	"A:FILTER": vmArrFilter,
	"A:EACH":   vmArrEach,
	"A:JOIN":   vmArrJoin,
	"A:COPY":   vmArrCopy,
	"A:EMPTY":  vmArrEmpty,
	"A:FIRST":  vmArrFirst,
	"A:LAST":   vmArrLast,
	"A:SLICE":  vmArrSlice,

	// --- Numeric methods ---
	"N:STR":   vmNumStr,
	"N:ROUND": vmNumRound,
	"N:INT":   vmNumInt,
	"N:ABS":   vmNumAbs,
	"N:SQRT":  vmNumSqrt,
	"N:COPY":  vmNumCopy,

	// --- Hash methods ---
	"H:KEYS":   vmHashKeys,
	"H:VALUES": vmHashValues,
	"H:HAS":    vmHashHas,
	"H:LEN":    vmHashLen,
	"H:COPY":   vmHashCopy,
	"H:DELETE": vmHashDelete,
	"H:EMPTY":  vmHashEmpty,

	// --- Any type ---
	"*:COPY":    vmAnyCopy,
	"*:TYPE":    vmAnyType,
	"*:ISNIL":   vmAnyIsNil,
	"*:TOSTR":   vmAnyToStr,
	"*:CLASSNAME": vmAnyClassName,
}

// SendBuiltin tries to dispatch a method call on a basic type.
// Returns (result, true) if handled, (nil, false) if not.
func SendBuiltin(t *Thread, self Value, method string, args []Value) (Value, bool) {
	upper := strings.ToUpper(method)

	// Determine type prefix
	var prefix string
	switch {
	case self.IsString():
		prefix = "S"
	case self.IsArray():
		prefix = "A"
	case self.IsNumeric():
		prefix = "N"
	case self.IsHash():
		prefix = "H"
	default:
		prefix = "*"
	}

	// Try type-specific method
	key := prefix + ":" + upper
	if fn, ok := builtinMethods[key]; ok {
		return fn(t, self, args), true
	}

	// Try wildcard method
	key = "*:" + upper
	if fn, ok := builtinMethods[key]; ok {
		return fn(t, self, args), true
	}

	return MakeNil(), false
}

// ========= String methods =========

func vmStrUpper(t *Thread, self Value, args []Value) Value {
	return MakeString(strings.ToUpper(self.AsString()))
}

func vmStrLower(t *Thread, self Value, args []Value) Value {
	return MakeString(strings.ToLower(self.AsString()))
}

func vmStrTrim(t *Thread, self Value, args []Value) Value {
	return MakeString(strings.TrimSpace(self.AsString()))
}

func vmStrLTrim(t *Thread, self Value, args []Value) Value {
	return MakeString(strings.TrimLeft(self.AsString(), " "))
}

func vmStrRTrim(t *Thread, self Value, args []Value) Value {
	return MakeString(strings.TrimRight(self.AsString(), " "))
}

func vmStrLeft(t *Thread, self Value, args []Value) Value {
	s := self.AsString()
	n := argInt(args, 0, len(s))
	if n > len(s) {
		n = len(s)
	}
	if n < 0 {
		n = 0
	}
	return MakeString(s[:n])
}

func vmStrRight(t *Thread, self Value, args []Value) Value {
	s := self.AsString()
	n := argInt(args, 0, len(s))
	if n > len(s) {
		n = len(s)
	}
	if n < 0 {
		n = 0
	}
	return MakeString(s[len(s)-n:])
}

func vmStrSubstr(t *Thread, self Value, args []Value) Value {
	s := self.AsString()
	start := argInt(args, 0, 1) - 1 // 1-based to 0-based
	length := argInt(args, 1, len(s)-start)
	if start < 0 {
		start = 0
	}
	if start >= len(s) {
		return MakeString("")
	}
	end := start + length
	if end > len(s) {
		end = len(s)
	}
	return MakeString(s[start:end])
}

func vmStrLen(t *Thread, self Value, args []Value) Value {
	return MakeInt(len(self.AsString()))
}

func vmStrReplace(t *Thread, self Value, args []Value) Value {
	old := argStr(args, 0, "")
	new := argStr(args, 1, "")
	return MakeString(strings.ReplaceAll(self.AsString(), old, new))
}

func vmStrSplit(t *Thread, self Value, args []Value) Value {
	sep := argStr(args, 0, ",")
	parts := strings.Split(self.AsString(), sep)
	items := make([]Value, len(parts))
	for i, p := range parts {
		items[i] = MakeString(p)
	}
	return MakeArrayFrom(items)
}

func vmStrContains(t *Thread, self Value, args []Value) Value {
	return MakeBool(strings.Contains(self.AsString(), argStr(args, 0, "")))
}

func vmStrStarts(t *Thread, self Value, args []Value) Value {
	return MakeBool(strings.HasPrefix(self.AsString(), argStr(args, 0, "")))
}

func vmStrEnds(t *Thread, self Value, args []Value) Value {
	return MakeBool(strings.HasSuffix(self.AsString(), argStr(args, 0, "")))
}

func vmStrReverse(t *Thread, self Value, args []Value) Value {
	runes := []rune(self.AsString())
	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]
	}
	return MakeString(string(runes))
}

func vmStrReplicate(t *Thread, self Value, args []Value) Value {
	n := argInt(args, 0, 1)
	return MakeString(strings.Repeat(self.AsString(), n))
}

func vmStrCopy(t *Thread, self Value, args []Value) Value {
	s := self.AsString()
	return MakeString(strings.Clone(s))
}

func vmStrAt(t *Thread, self Value, args []Value) Value {
	sub := argStr(args, 0, "")
	return MakeInt(strings.Index(self.AsString(), sub) + 1) // 1-based
}

func vmStrEmpty(t *Thread, self Value, args []Value) Value {
	return MakeBool(len(strings.TrimSpace(self.AsString())) == 0)
}

func vmStrVal(t *Thread, self Value, args []Value) Value {
	s := strings.TrimSpace(self.AsString())
	if f, err := parseStrToFloat(s); err == nil {
		return MakeDoubleAuto(f)
	}
	return MakeInt(0)
}

// ========= Array methods =========

func vmArrLen(t *Thread, self Value, args []Value) Value {
	return MakeInt(len(self.AsArray().Items))
}

func vmArrPush(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	for _, a := range args {
		arr.Items = append(arr.Items, a)
	}
	return self // return self for chaining
}

func vmArrPop(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	if len(arr.Items) == 0 {
		return MakeNil()
	}
	last := arr.Items[len(arr.Items)-1]
	arr.Items = arr.Items[:len(arr.Items)-1]
	return last
}

func vmArrSort(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	items := make([]Value, len(arr.Items))
	copy(items, arr.Items)
	sort.SliceStable(items, func(i, j int) bool {
		a, b := items[i], items[j]
		if a.IsString() && b.IsString() {
			return a.AsString() < b.AsString()
		}
		if a.IsNumeric() && b.IsNumeric() {
			return a.AsNumDouble() < b.AsNumDouble()
		}
		return false
	})
	return MakeArrayFrom(items)
}

func vmArrFind(t *Thread, self Value, args []Value) Value {
	if len(args) == 0 {
		return MakeInt(0)
	}
	target := args[0]
	for i, item := range self.AsArray().Items {
		if valuesEqual(item, target) {
			return MakeInt(i + 1) // 1-based
		}
	}
	return MakeInt(0)
}

func vmArrMap(t *Thread, self Value, args []Value) Value {
	if len(args) == 0 || !args[0].IsBlock() {
		return self
	}
	blk := args[0].AsBlock()
	arr := self.AsArray()
	result := make([]Value, len(arr.Items))
	for i, item := range arr.Items {
		t.push(item)
		t.PendingParams2(1)
		blk.Fn(t)
		result[i] = t.pop()
	}
	return MakeArrayFrom(result)
}

func vmArrFilter(t *Thread, self Value, args []Value) Value {
	if len(args) == 0 || !args[0].IsBlock() {
		return self
	}
	blk := args[0].AsBlock()
	arr := self.AsArray()
	var result []Value
	for _, item := range arr.Items {
		t.push(item)
		t.PendingParams2(1)
		blk.Fn(t)
		keep := t.pop()
		if keep.AsBool() {
			result = append(result, item)
		}
	}
	return MakeArrayFrom(result)
}

func vmArrEach(t *Thread, self Value, args []Value) Value {
	if len(args) == 0 || !args[0].IsBlock() {
		return self
	}
	blk := args[0].AsBlock()
	for _, item := range self.AsArray().Items {
		t.push(item)
		t.PendingParams2(1)
		blk.Fn(t)
		t.pop() // discard result
	}
	return self // return self for chaining
}

func vmArrJoin(t *Thread, self Value, args []Value) Value {
	sep := argStr(args, 0, ",")
	arr := self.AsArray()
	parts := make([]string, len(arr.Items))
	for i, item := range arr.Items {
		parts[i] = item.AsString()
	}
	return MakeString(strings.Join(parts, sep))
}

func vmArrCopy(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	items := make([]Value, len(arr.Items))
	copy(items, arr.Items)
	return MakeArrayFrom(items)
}

func vmArrEmpty(t *Thread, self Value, args []Value) Value {
	return MakeBool(len(self.AsArray().Items) == 0)
}

func vmArrFirst(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	if len(arr.Items) > 0 {
		return arr.Items[0]
	}
	return MakeNil()
}

func vmArrLast(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	if len(arr.Items) > 0 {
		return arr.Items[len(arr.Items)-1]
	}
	return MakeNil()
}

func vmArrSlice(t *Thread, self Value, args []Value) Value {
	arr := self.AsArray()
	from := argInt(args, 0, 1) - 1 // 1-based to 0-based
	to := argInt(args, 1, len(arr.Items))
	if from < 0 {
		from = 0
	}
	if to > len(arr.Items) {
		to = len(arr.Items)
	}
	items := make([]Value, to-from)
	copy(items, arr.Items[from:to])
	return MakeArrayFrom(items)
}

// ========= Numeric methods =========

func vmNumStr(t *Thread, self Value, args []Value) Value {
	width := argInt(args, 0, 10)
	dec := argInt(args, 1, 0)
	return MakeString(fmt.Sprintf("%*.*f", width, dec, self.AsNumDouble()))
}

func vmNumRound(t *Thread, self Value, args []Value) Value {
	dec := argInt(args, 0, 0)
	mul := math.Pow(10, float64(dec))
	return MakeDoubleAuto(math.Round(self.AsNumDouble()*mul) / mul)
}

func vmNumInt(t *Thread, self Value, args []Value) Value {
	return MakeInt(int(self.AsNumDouble()))
}

func vmNumAbs(t *Thread, self Value, args []Value) Value {
	return MakeDoubleAuto(math.Abs(self.AsNumDouble()))
}

func vmNumSqrt(t *Thread, self Value, args []Value) Value {
	return MakeDoubleAuto(math.Sqrt(self.AsNumDouble()))
}

func vmNumCopy(t *Thread, self Value, args []Value) Value {
	return self // numeric values are immutable
}

// ========= Hash methods =========

func vmHashKeys(t *Thread, self Value, args []Value) Value {
	h := self.AsHash()
	items := make([]Value, len(h.Keys))
	copy(items, h.Keys)
	return MakeArrayFrom(items)
}

func vmHashValues(t *Thread, self Value, args []Value) Value {
	h := self.AsHash()
	items := make([]Value, len(h.Values))
	copy(items, h.Values)
	return MakeArrayFrom(items)
}

func vmHashHas(t *Thread, self Value, args []Value) Value {
	if len(args) == 0 {
		return MakeBool(false)
	}
	return MakeBool(self.AsHash().Has(args[0]))
}

func vmHashLen(t *Thread, self Value, args []Value) Value {
	return MakeInt(len(self.AsHash().Keys))
}

func vmHashCopy(t *Thread, self Value, args []Value) Value {
	h := self.AsHash()
	nh := &HbHash{
		Keys:   make([]Value, len(h.Keys)),
		Values: make([]Value, len(h.Values)),
	}
	copy(nh.Keys, h.Keys)
	copy(nh.Values, h.Values)
	// Index is rebuilt lazily on first Lookup against nh.
	return MakeHashFrom(nh)
}

func vmHashDelete(t *Thread, self Value, args []Value) Value {
	if len(args) == 0 {
		return self
	}
	self.AsHash().Delete(args[0])
	return self
}

func vmHashEmpty(t *Thread, self Value, args []Value) Value {
	return MakeBool(len(self.AsHash().Keys) == 0)
}

// ========= Any type methods =========

func vmAnyCopy(t *Thread, self Value, args []Value) Value {
	// Generic copy — delegates to type-specific
	switch {
	case self.IsString():
		return vmStrCopy(t, self, args)
	case self.IsArray():
		return vmArrCopy(t, self, args)
	case self.IsHash():
		return vmHashCopy(t, self, args)
	default:
		return self // immutable types return self
	}
}

func vmAnyType(t *Thread, self Value, args []Value) Value {
	switch {
	case self.IsNil():
		return MakeString("U")
	case self.IsString():
		return MakeString("C")
	case self.IsNumeric():
		return MakeString("N")
	case self.IsLogical():
		return MakeString("L")
	case self.IsDate():
		return MakeString("D")
	case self.IsArray():
		return MakeString("A")
	case self.IsHash():
		return MakeString("H")
	case self.IsBlock():
		return MakeString("B")
	default:
		return MakeString("U")
	}
}

func vmAnyIsNil(t *Thread, self Value, args []Value) Value {
	return MakeBool(self.IsNil())
}

func vmAnyToStr(t *Thread, self Value, args []Value) Value {
	switch {
	case self.IsString():
		return self
	case self.IsNumeric():
		return MakeString(fmt.Sprintf("%v", self.AsNumDouble()))
	case self.IsLogical():
		if self.AsBool() {
			return MakeString(".T.")
		}
		return MakeString(".F.")
	case self.IsNil():
		return MakeString("NIL")
	default:
		return MakeString(fmt.Sprintf("%v", self))
	}
}

func vmAnyClassName(t *Thread, self Value, args []Value) Value {
	if self.IsObject() {
		cls := GetClass(self.AsArray().Class)
		if cls != nil {
			return MakeString(cls.Name)
		}
	}
	return MakeString("")
}

// ========= Helpers =========

func argInt(args []Value, index, def int) int {
	if index < len(args) && args[index].IsNumeric() {
		return args[index].AsInt()
	}
	return def
}

func argStr(args []Value, index int, def string) string {
	if index < len(args) && args[index].IsString() {
		return args[index].AsString()
	}
	return def
}

func valuesEqual(a, b Value) bool {
	if a.IsString() && b.IsString() {
		return a.AsString() == b.AsString()
	}
	if a.IsNumeric() && b.IsNumeric() {
		return a.AsNumDouble() == b.AsNumDouble()
	}
	if a.IsLogical() && b.IsLogical() {
		return a.AsBool() == b.AsBool()
	}
	return a.IsNil() && b.IsNil()
}

func parseStrToFloat(s string) (float64, error) {
	var result float64
	_, err := fmt.Sscanf(s, "%f", &result)
	return result, err
}