package queue

import (
	"context"
	"sync"
	"time"
)

type IdempotencyState string

const (
	IdempotencyStateAcquired   IdempotencyState = "acquired"
	IdempotencyStateDuplicate  IdempotencyState = "duplicate"
	IdempotencyStateInProgress IdempotencyState = "in_progress"
)

type IdempotencyStore interface {
	Acquire(ctx context.Context, key string, processingTTL time.Duration) (IdempotencyState, error)
	MarkCompleted(ctx context.Context, key string, ttl time.Duration) error
	Release(ctx context.Context, key string) error
}

type NoopIdempotencyStore struct{}

func (NoopIdempotencyStore) Acquire(context.Context, string, time.Duration) (IdempotencyState, error) {
	return IdempotencyStateAcquired, nil
}

func (NoopIdempotencyStore) MarkCompleted(context.Context, string, time.Duration) error {
	return nil
}

func (NoopIdempotencyStore) Release(context.Context, string) error {
	return nil
}

type MemoryIdempotencyStore struct {
	mu      sync.Mutex
	records map[string]memoryIdempotencyRecord
	now     func() time.Time
}

type memoryIdempotencyRecord struct {
	state     IdempotencyState
	expiresAt time.Time
}

func NewMemoryIdempotencyStore() *MemoryIdempotencyStore {
	return &MemoryIdempotencyStore{
		records: make(map[string]memoryIdempotencyRecord),
		now:     func() time.Time { return time.Now().UTC() },
	}
}

func (s *MemoryIdempotencyStore) Acquire(_ context.Context, key string, processingTTL time.Duration) (IdempotencyState, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.cleanupExpiredLocked()
	if record, ok := s.records[key]; ok {
		return record.state, nil
	}
	s.records[key] = memoryIdempotencyRecord{
		state:     IdempotencyStateInProgress,
		expiresAt: s.now().Add(processingTTL),
	}
	return IdempotencyStateAcquired, nil
}

func (s *MemoryIdempotencyStore) MarkCompleted(_ context.Context, key string, ttl time.Duration) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.records[key] = memoryIdempotencyRecord{
		state:     IdempotencyStateDuplicate,
		expiresAt: s.now().Add(ttl),
	}
	return nil
}

func (s *MemoryIdempotencyStore) Release(_ context.Context, key string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	delete(s.records, key)
	return nil
}

func (s *MemoryIdempotencyStore) cleanupExpiredLocked() {
	now := s.now()
	for key, record := range s.records {
		if !record.expiresAt.IsZero() && now.After(record.expiresAt) {
			delete(s.records, key)
		}
	}
}