package main

import "sync"

type RemoteGrainPool struct {
	mu     sync.RWMutex
	Host   string
	grains map[CartId]*RemoteGrain
}

func NewRemoteGrainPool(addr string) *RemoteGrainPool {
	return &RemoteGrainPool{
		Host:   addr,
		grains: make(map[CartId]*RemoteGrain),
	}
}

func (p *RemoteGrainPool) findRemoteGrain(id CartId) *RemoteGrain {
	p.mu.RLock()
	grain, ok := p.grains[id]
	p.mu.RUnlock()
	if !ok {
		return nil
	}
	return grain
}

func (p *RemoteGrainPool) findOrCreateGrain(id CartId) (*RemoteGrain, error) {
	grain := p.findRemoteGrain(id)

	if grain == nil {
		grain, err := NewRemoteGrain(id, p.Host)
		if err != nil {
			return nil, err
		}
		p.mu.Lock()
		p.grains[id] = grain
		p.mu.Unlock()
	}
	return grain, nil
}

func (p *RemoteGrainPool) Delete(id CartId) {
	p.mu.Lock()
	delete(p.grains, id)
	p.mu.Unlock()
}

func (p *RemoteGrainPool) Process(id CartId, messages ...Message) (*FrameWithPayload, error) {
	var result *FrameWithPayload
	grain, err := p.findOrCreateGrain(id)
	if err != nil {
		return nil, err
	}
	for _, message := range messages {
		result, err = grain.HandleMessage(&message, false)
	}
	return result, err
}

func (p *RemoteGrainPool) Get(id CartId) (*FrameWithPayload, error) {
	grain, err := p.findOrCreateGrain(id)
	if err != nil {
		return nil, err
	}
	return grain.GetCurrentState()
}