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

// Collection operations for the Five runtime.
// Array generation, indexing, hash generation, and code block evaluation.
// Harbour: HB_P_ARRAYGEN, HB_P_ARRAYPUSH, HB_P_ARRAYPOP, etc.
package hbrt

import "unsafe"

// ArrayGen pops n items from stack and creates an array.
// Harbour: HB_P_ARRAYGEN / hb_vmArrayGen
func (t *Thread) ArrayGen(n int) {
	items := make([]Value, n)
	for i := n - 1; i >= 0; i-- {
		items[i] = t.pop()
	}
	t.push(MakeArrayFrom(items))
}

// HashGen pops n key-value pairs and creates a hash.
// Stack: [key1] [val1] [key2] [val2] ... → Hash
func (t *Thread) HashGen(n int) {
	hh := &HbHash{
		Keys:   make([]Value, n),
		Values: make([]Value, n),
	}
	for i := n - 1; i >= 0; i-- {
		hh.Values[i] = t.pop()
		hh.Keys[i] = t.pop()
	}
	t.push(Value{
		info: makeInfo(tHash, 0, 0),
		ptr:  unsafe.Pointer(hh),
	})
}

// ArrayPush pops index and array, pushes array[index].
// Harbour: HB_P_ARRAYPUSH
func (t *Thread) ArrayPush() {
	idx := t.pop()
	arr := t.pop()

	if !arr.IsArray() {
		panic(t.argError("[]", arr, idx))
	}
	ha := arr.AsArray()
	n := int(idx.AsNumInt())

	// Harbour: 1-based indexing
	if n < 1 || n > len(ha.Items) {
		panic(t.runtimeError("array index out of bounds"))
	}
	t.push(ha.Items[n-1])
}

// ArrayPop pops value, index, array and sets array[index] = value.
// Harbour: HB_P_ARRAYPOP
func (t *Thread) ArrayPop() {
	val := t.pop()
	idx := t.pop()
	arr := t.pop()

	if !arr.IsArray() {
		panic(t.argError("[]=", arr, idx))
	}
	ha := arr.AsArray()
	n := int(idx.AsNumInt())

	if n < 1 || n > len(ha.Items) {
		panic(t.runtimeError("array index out of bounds"))
	}
	ha.Items[n-1] = val
}

// EvalBlock evaluates a code block on the stack with nArgs arguments.
// Stack: [block] [arg1] ... [argN] → [result]
func (t *Thread) EvalBlock(nArgs int) {
	args := make([]Value, nArgs)
	for i := nArgs - 1; i >= 0; i-- {
		args[i] = t.pop()
	}
	blockVal := t.pop()
	if !blockVal.IsBlock() {
		panic(t.argError("Eval", blockVal))
	}
	blk := blockVal.AsBlock()

	// Push args for Frame
	for _, arg := range args {
		t.push(arg)
	}

	t.pendingParams = nArgs
	blk.Fn(t)
	t.push(t.retVal)
}

// PushBlock creates a code block and pushes it onto the stack.
func (t *Thread) PushBlock(fn func(*Thread), detachedLocals int) {
	t.push(MakeBlock(fn, detachedLocals))
}

// PushSelf pushes the current Self object (for :: access in methods).
func (t *Thread) PushSelf() {
	t.push(t.self)
}