package storage

import (
	"context"
	"sort"
	"sync"
	"time"

	"github.com/google/uuid"
)

// MemoryStore is an in-memory implementation of Store for use in tests.
type MemoryStore struct {
	mu            sync.Mutex
	LoginAttempts []LoginAttempt
	Sessions      map[string]*Session
	SessionLogs   []SessionLog
}

// NewMemoryStore returns a new empty MemoryStore.
func NewMemoryStore() *MemoryStore {
	return &MemoryStore{
		Sessions: make(map[string]*Session),
	}
}

func (m *MemoryStore) RecordLoginAttempt(_ context.Context, username, password, ip string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	now := time.Now().UTC()
	for i := range m.LoginAttempts {
		a := &m.LoginAttempts[i]
		if a.Username == username && a.Password == password && a.IP == ip {
			a.Count++
			a.LastSeen = now
			return nil
		}
	}

	m.LoginAttempts = append(m.LoginAttempts, LoginAttempt{
		ID:        int64(len(m.LoginAttempts) + 1),
		Username:  username,
		Password:  password,
		IP:        ip,
		Count:     1,
		FirstSeen: now,
		LastSeen:  now,
	})
	return nil
}

func (m *MemoryStore) CreateSession(_ context.Context, ip, username, shellName string) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	id := uuid.New().String()
	now := time.Now().UTC()
	m.Sessions[id] = &Session{
		ID:          id,
		IP:          ip,
		Username:    username,
		ShellName:   shellName,
		ConnectedAt: now,
	}
	return id, nil
}

func (m *MemoryStore) EndSession(_ context.Context, sessionID string, disconnectedAt time.Time) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if s, ok := m.Sessions[sessionID]; ok {
		t := disconnectedAt.UTC()
		s.DisconnectedAt = &t
	}
	return nil
}

func (m *MemoryStore) UpdateHumanScore(_ context.Context, sessionID string, score float64) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if s, ok := m.Sessions[sessionID]; ok {
		s.HumanScore = &score
	}
	return nil
}

func (m *MemoryStore) AppendSessionLog(_ context.Context, sessionID, input, output string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.SessionLogs = append(m.SessionLogs, SessionLog{
		ID:        int64(len(m.SessionLogs) + 1),
		SessionID: sessionID,
		Timestamp: time.Now().UTC(),
		Input:     input,
		Output:    output,
	})
	return nil
}

func (m *MemoryStore) DeleteRecordsBefore(_ context.Context, cutoff time.Time) (int64, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	var total int64

	// Delete old login attempts.
	kept := m.LoginAttempts[:0]
	for _, a := range m.LoginAttempts {
		if a.LastSeen.Before(cutoff) {
			total++
		} else {
			kept = append(kept, a)
		}
	}
	m.LoginAttempts = kept

	// Delete old sessions and their logs.
	for id, s := range m.Sessions {
		if s.ConnectedAt.Before(cutoff) {
			delete(m.Sessions, id)
			total++
		}
	}

	keptLogs := m.SessionLogs[:0]
	for _, l := range m.SessionLogs {
		if _, ok := m.Sessions[l.SessionID]; ok {
			keptLogs = append(keptLogs, l)
		} else {
			total++
		}
	}
	m.SessionLogs = keptLogs

	return total, nil
}

func (m *MemoryStore) GetDashboardStats(_ context.Context) (*DashboardStats, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	stats := &DashboardStats{}
	ips := make(map[string]struct{})
	for _, a := range m.LoginAttempts {
		stats.TotalAttempts += int64(a.Count)
		ips[a.IP] = struct{}{}
	}
	stats.UniqueIPs = int64(len(ips))
	stats.TotalSessions = int64(len(m.Sessions))
	for _, s := range m.Sessions {
		if s.DisconnectedAt == nil {
			stats.ActiveSessions++
		}
	}
	return stats, nil
}

func (m *MemoryStore) GetTopUsernames(_ context.Context, limit int) ([]TopEntry, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.topN("username", limit), nil
}

func (m *MemoryStore) GetTopPasswords(_ context.Context, limit int) ([]TopEntry, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.topN("password", limit), nil
}

func (m *MemoryStore) GetTopIPs(_ context.Context, limit int) ([]TopEntry, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.topN("ip", limit), nil
}

// topN aggregates login attempts by the given field and returns the top N. Must be called with m.mu held.
func (m *MemoryStore) topN(field string, limit int) []TopEntry {
	counts := make(map[string]int64)
	for _, a := range m.LoginAttempts {
		var key string
		switch field {
		case "username":
			key = a.Username
		case "password":
			key = a.Password
		case "ip":
			key = a.IP
		}
		counts[key] += int64(a.Count)
	}

	entries := make([]TopEntry, 0, len(counts))
	for k, v := range counts {
		entries = append(entries, TopEntry{Value: k, Count: v})
	}
	sort.Slice(entries, func(i, j int) bool {
		return entries[i].Count > entries[j].Count
	})
	if limit > 0 && len(entries) > limit {
		entries = entries[:limit]
	}
	return entries
}

func (m *MemoryStore) GetRecentSessions(_ context.Context, limit int, activeOnly bool) ([]Session, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	var sessions []Session
	for _, s := range m.Sessions {
		if activeOnly && s.DisconnectedAt != nil {
			continue
		}
		sessions = append(sessions, *s)
	}
	sort.Slice(sessions, func(i, j int) bool {
		return sessions[i].ConnectedAt.After(sessions[j].ConnectedAt)
	})
	if limit > 0 && len(sessions) > limit {
		sessions = sessions[:limit]
	}
	return sessions, nil
}

func (m *MemoryStore) Close() error {
	return nil
}