package check

import (
	"context"
	"sort"
	"sync"
)

// memKV is a bucket in memory with the revisions a real one gives.
type memKV struct {
	mu   sync.Mutex
	vals map[string][]byte
	revs map[string]uint64
	next uint64
	// creates counts the creates that succeeded, by key.
	creates map[string]int
}

func newMemKV() *memKV {
	return &memKV{vals: map[string][]byte{}, revs: map[string]uint64{}, creates: map[string]int{}}
}

func (m *memKV) Get(_ context.Context, key string) ([]byte, uint64, bool, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	v, ok := m.vals[key]
	return v, m.revs[key], ok, nil
}

func (m *memKV) Create(_ context.Context, key string, value []byte) (uint64, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if _, ok := m.vals[key]; ok {
		return 0, ErrConflict
	}
	m.next++
	m.vals[key], m.revs[key] = append([]byte(nil), value...), m.next
	m.creates[key]++
	return m.next, nil
}

func (m *memKV) Update(_ context.Context, key string, value []byte, revision uint64) (uint64, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if _, ok := m.vals[key]; !ok || m.revs[key] != revision {
		return 0, ErrConflict
	}
	m.next++
	m.vals[key], m.revs[key] = append([]byte(nil), value...), m.next
	return m.next, nil
}

func (m *memKV) Keys(context.Context) ([]string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	keys := make([]string, 0, len(m.vals))
	for k := range m.vals {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys, nil
}