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

// Goroutine support for Five runtime.
// Provides Go's goroutine, channel, and WaitGroup primitives
// as first-class Harbour values.

package hbrt

import (
	"fmt"
	"os"
	"sync"
)

// --- Channel ---

// HbChannel wraps Go's chan Value for use in PRG code.
type HbChannel struct {
	Ch        chan Value
	closeOnce sync.Once
	closed    bool
}

// MakeChannel creates a channel Value with optional buffer size.
func MakeChannel(size int) Value {
	return MakePointer(&HbChannel{Ch: make(chan Value, size)})
}

// AsChannel extracts HbChannel from a Pointer value.
func (v Value) AsChannel() *HbChannel {
	if !v.IsPointer() {
		return nil
	}
	if ch, ok := v.AsPointer().(*HbChannel); ok {
		return ch
	}
	return nil
}

// Send sends a value into the channel. Safe if channel is closed (recovers panic).
func (ch *HbChannel) Send(val Value) {
	defer func() {
		if r := recover(); r != nil {
			// send on closed channel — silently ignore
		}
	}()
	ch.Ch <- val
}

// Receive receives a value from the channel.
func (ch *HbChannel) Receive() Value {
	v, ok := <-ch.Ch
	if !ok {
		return MakeNil() // channel closed
	}
	return v
}

// TryReceive attempts non-blocking receive. Returns (value, true) or (nil, false).
func (ch *HbChannel) TryReceive() (Value, bool) {
	select {
	case v, ok := <-ch.Ch:
		if !ok {
			return MakeNil(), false
		}
		return v, true
	default:
		return MakeNil(), false
	}
}

// Close closes the channel. Safe to call multiple times.
func (ch *HbChannel) Close() {
	ch.closeOnce.Do(func() {
		ch.closed = true
		close(ch.Ch)
	})
}

// IsClosed returns true if the channel has been closed.
func (ch *HbChannel) IsClosed() bool {
	return ch.closed
}

// --- WaitGroup ---

// HbWaitGroup wraps sync.WaitGroup.
type HbWaitGroup struct {
	WG sync.WaitGroup
}

// MakeWaitGroup creates a WaitGroup Value with initial count.
func MakeWaitGroup(n int) Value {
	wg := &HbWaitGroup{}
	if n > 0 {
		wg.WG.Add(n)
	}
	return MakePointer(wg)
}

// AsWaitGroup extracts HbWaitGroup from a Pointer value.
func (v Value) AsWaitGroup() *HbWaitGroup {
	if !v.IsPointer() {
		return nil
	}
	if wg, ok := v.AsPointer().(*HbWaitGroup); ok {
		return wg
	}
	return nil
}

// --- Mutex ---

// HbMutex wraps sync.Mutex.
type HbMutex struct {
	Mu sync.Mutex
}

// MakeMutex creates a Mutex Value.
func MakeMutex() Value {
	return MakePointer(&HbMutex{})
}

// AsMutex extracts HbMutex from a Pointer value.
func (v Value) AsMutex() *HbMutex {
	if !v.IsPointer() {
		return nil
	}
	if mu, ok := v.AsPointer().(*HbMutex); ok {
		return mu
	}
	return nil
}

// --- GoRoutine launcher ---

// GoLaunch spawns a new goroutine that runs a function on a new Thread.
func (vm *VM) GoLaunch(fn func(*Thread), args []Value) {
	go func() {
		defer func() {
			if r := recover(); r != nil {
				fmt.Fprintf(os.Stderr, "Five goroutine panic: %v\n", r)
			}
		}()
		t := vm.NewThread()
		for _, a := range args {
			t.push(a)
		}
		t.PendingParams2(len(args))
		fn(t)
	}()
}

// GoLaunchBlock spawns a goroutine that evaluates a code block.
func (vm *VM) GoLaunchBlock(blk *HbBlock, args []Value) {
	go func() {
		defer func() {
			if r := recover(); r != nil {
				fmt.Fprintf(os.Stderr, "Five goroutine panic: %v\n", r)
			}
		}()
		t := vm.NewThread()
		for _, a := range args {
			t.push(a)
		}
		t.PendingParams2(len(args))
		blk.Fn(t)
	}()
}