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

// Array functions for the Five runtime library.
// Implements Harbour-compatible array manipulation functions.
// Reference: /mnt/d/harbour-core/src/vm/arrays.c
package hbrtl

import (
	"five/hbrt"
	"sort"
)

// AAdd appends an element to an array and returns the array.
// Harbour: AAdd(aArray, xValue) → aArray
func AAdd(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	arrVal := t.Local(1)
	val := t.Local(2)
	if !arrVal.IsArray() {
		panic("AAdd: argument is not an array")
	}
	arr := arrVal.AsArray()
	arr.Items = append(arr.Items, val)
	t.PushValue(arrVal)
	t.RetValue()
}

// ADel deletes an element from array at position, shifts remaining left.
// Harbour: ADel(aArray, nPos) → aArray
func ADel(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	arrVal := t.Local(1)
	pos := int(t.Local(2).AsNumInt())
	arr := arrVal.AsArray()
	if pos >= 1 && pos <= len(arr.Items) {
		copy(arr.Items[pos-1:], arr.Items[pos:])
		arr.Items[len(arr.Items)-1] = hbrt.MakeNil()
	}
	t.PushValue(arrVal)
	t.RetValue()
}

// AIns inserts NIL at position, shifts elements right.
// Harbour: AIns(aArray, nPos) → aArray
func AIns(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	arrVal := t.Local(1)
	pos := int(t.Local(2).AsNumInt())
	arr := arrVal.AsArray()
	if pos >= 1 && pos <= len(arr.Items) {
		copy(arr.Items[pos:], arr.Items[pos-1:len(arr.Items)-1])
		arr.Items[pos-1] = hbrt.MakeNil()
	}
	t.PushValue(arrVal)
	t.RetValue()
}

// ASize resizes an array.
// Harbour: ASize(aArray, nLen) → aArray
func ASize(t *hbrt.Thread) {
	t.Frame(2, 0)
	defer t.EndProc()
	arrVal := t.Local(1)
	newLen := int(t.Local(2).AsNumInt())
	arr := arrVal.AsArray()
	if newLen < 0 {
		newLen = 0
	}
	if newLen > len(arr.Items) {
		ext := make([]hbrt.Value, newLen-len(arr.Items))
		arr.Items = append(arr.Items, ext...)
	} else {
		arr.Items = arr.Items[:newLen]
	}
	t.PushValue(arrVal)
	t.RetValue()
}

// AClone creates a shallow copy of an array.
// Harbour: AClone(aArray) → aNewArray
func AClone(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	arrVal := t.Local(1)
	if !arrVal.IsArray() {
		t.PushValue(arrVal)
		t.RetValue()
		return
	}
	src := arrVal.AsArray()
	items := make([]hbrt.Value, len(src.Items))
	copy(items, src.Items)
	t.PushValue(hbrt.MakeArrayFrom(items))
	t.RetValue()
}

// ACopy copies elements from one array to another.
// Harbour: ACopy(aSource, aDest [, nStart [, nCount [, nTargetPos]]]) → aDest
func ACopy(t *hbrt.Thread) {
	t.Frame(2, 0) // simplified: just source and dest
	defer t.EndProc()
	srcVal := t.Local(1)
	dstVal := t.Local(2)
	src := srcVal.AsArray()
	dst := dstVal.AsArray()
	n := len(src.Items)
	if n > len(dst.Items) {
		n = len(dst.Items)
	}
	copy(dst.Items[:n], src.Items[:n])
	t.PushValue(dstVal)
	t.RetValue()
}

// AFill fills an array with a value.
// Harbour: AFill(aArray, xValue [, nStart [, nCount]]) → aArray
func AFill(t *hbrt.Thread) {
	t.Frame(2, 0) // simplified: array and value
	defer t.EndProc()
	arrVal := t.Local(1)
	val := t.Local(2)
	arr := arrVal.AsArray()
	for i := range arr.Items {
		arr.Items[i] = val
	}
	t.PushValue(arrVal)
	t.RetValue()
}

// ASort sorts an array using an optional comparison block.
// Harbour: ASort(aArray [, nStart [, nCount [, bBlock]]]) → aArray
func ASort(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	arrVal := t.Local(1)
	arr := arrVal.AsArray()

	if nParams >= 4 && t.Local(4).IsBlock() {
		// Sort with code block comparator
		blk := t.Local(4).AsBlock()
		sort.SliceStable(arr.Items, func(i, j int) bool {
			t.PushValue(arr.Items[i])
			t.PushValue(arr.Items[j])
			t.PendingParams2(2)
			blk.Fn(t)
			return t.GetRetValue().AsBool()
		})
	} else {
		// Default sort: by value comparison
		sort.SliceStable(arr.Items, func(i, j int) bool {
			a, b := arr.Items[i], arr.Items[j]
			if a.IsString() && b.IsString() {
				return a.AsString() < b.AsString()
			}
			if a.IsNumeric() && b.IsNumeric() {
				return a.AsNumDouble() < b.AsNumDouble()
			}
			return false
		})
	}

	t.PushValue(arrVal)
	t.RetValue()
}

// AEval evaluates a block for each element in array.
// Harbour: AEval(aArray, bBlock [, nStart [, nCount]]) → aArray
func AEval(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	arrVal := t.Local(1)
	arr := arrVal.AsArray()
	blkVal := t.Local(2)
	if !blkVal.IsBlock() {
		t.PushValue(arrVal)
		t.RetValue()
		return
	}
	blk := blkVal.AsBlock()

	for i, item := range arr.Items {
		// Harbour: AEval callback receives (element, index).
		// Stack order: index first, element on top — Frame picks top-N.
		t.PushValue(hbrt.MakeInt(i + 1)) // arg2: 1-based index
		t.PushValue(item)                 // arg1: element value
		t.PendingParams2(2)
		blk.Fn(t)
	}

	t.PushValue(arrVal)
	t.RetValue()
}

// AScan searches for a value in array, returns position (0 if not found).
// Harbour: AScan(aArray, xValue|bBlock [, nStart [, nCount]]) → nPos
func AScan(t *hbrt.Thread) {
	nParams := t.ParamCount()
	t.Frame(nParams, 0)
	defer t.EndProc()

	arrVal := t.Local(1)
	arr := arrVal.AsArray()
	search := t.Local(2)

	if search.IsBlock() {
		blk := search.AsBlock()
		for i, item := range arr.Items {
			t.PushValue(item)
			t.PendingParams2(1)
			blk.Fn(t)
			if t.GetRetValue().AsBool() {
				t.RetInt(int64(i + 1))
				return
			}
		}
	} else {
		for i, item := range arr.Items {
			if valuesEqual(item, search) {
				t.RetInt(int64(i + 1))
				return
			}
		}
	}

	t.RetInt(0)
}

// ATail returns the last element of an array.
// Harbour: ATail(aArray) → xValue
func ATail(t *hbrt.Thread) {
	t.Frame(1, 0)
	defer t.EndProc()
	arr := t.Local(1).AsArray()
	if arr != nil && len(arr.Items) > 0 {
		t.PushValue(arr.Items[len(arr.Items)-1])
	} else {
		t.PushNil()
	}
	t.RetValue()
}

// valuesEqual compares two values for equality (simplified for AScan).
func valuesEqual(a, b hbrt.Value) bool {
	if a.Type() != b.Type() {
		if a.IsNumeric() && b.IsNumeric() {
			return a.AsNumDouble() == b.AsNumDouble()
		}
		return false
	}
	switch {
	case a.IsNumInt():
		return a.AsNumInt() == b.AsNumInt()
	case a.IsDouble():
		return a.AsDouble() == b.AsDouble()
	case a.IsString():
		return a.AsString() == b.AsString()
	case a.IsLogical():
		return a.AsBool() == b.AsBool()
	default:
		return false
	}
}