package store

import (
	"context"
	"sync"
)

// Memory is the Phase-1 in-process Store. Thread-safe via a single mutex.
type Memory struct {
	mu        sync.Mutex
	decisions map[string]Decision
}

// NewMemory returns an empty Memory store.
func NewMemory() *Memory {
	return &Memory{decisions: map[string]Decision{}}
}

// Reserve inserts d.DecisionID → d. On duplicate it returns ErrReplay
// and leaves the stored row untouched.
func (m *Memory) Reserve(_ context.Context, d Decision) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	if _, exists := m.decisions[d.DecisionID]; exists {
		return ErrReplay
	}
	m.decisions[d.DecisionID] = d
	return nil
}

// Get returns the stored decision, if any.
func (m *Memory) Get(_ context.Context, decisionID string) (Decision, bool, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	d, ok := m.decisions[decisionID]
	return d, ok, nil
}