// Package ws provides agent and contact online/offline presence tracking
// using Redis sorted sets and hashes. Mirrors Chatwoot's OnlineStatusTracker
// which uses Redis to track which agents/contacts are currently online.
package ws

import (
	"context"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/redis/go-redis/v9"

	"github.com/gochat/gochat/pkg/logger"
)

// PresenceTracker tracks online/offline status of agents and contacts
// using Redis sorted sets (score=timestamp) and hashes (member→status).
//
// Reference: Chatwoot OnlineStatusTracker — uses Redis to maintain:
//   - Online agents per account (for sidebar display)
//   - Online contacts per inbox (for real-time awareness)
//   - TTL-based expiry: agents expire after 20s, contacts after 90s
//     without heartbeat refresh
type PresenceTracker struct {
	rdb   *redis.Client
	relay *BroadcastRelay
}

// NewPresenceTracker creates a new presence tracker.
func NewPresenceTracker(rdb *redis.Client, relay *BroadcastRelay) *PresenceTracker {
	return &PresenceTracker{
		rdb:   rdb,
		relay: relay,
	}
}

// SetAgentOnline marks an agent as online for a given account.
// Adds the agent to the Redis sorted set with current timestamp as score,
// and sets their status in the presence hash.
//
// Reference: Chatwoot OnlineStatusTracker.set_agent_online — adds to
// Redis sorted set with score as epoch timestamp, refreshes on each heartbeat.
func (p *PresenceTracker) SetAgentOnline(ctx context.Context, agentID, accountID uint) error {
	member := presenceMember(agentID, accountID)
	now := float64(time.Now().Unix())

	// Add to sorted set (score = timestamp for expiry-based cleanup)
	if err := p.rdb.ZAdd(ctx, RedisKeyPresenceAgents, redis.Z{
		Score:  now,
		Member: member,
	}).Err(); err != nil {
		return fmt.Errorf("failed to set agent online: %w", err)
	}

	// Set status in hash
	if err := p.rdb.HSet(ctx, RedisKeyPresenceStatus, member, "online").Err(); err != nil {
		return fmt.Errorf("failed to set agent status: %w", err)
	}

	// Broadcast presence update event
	msg := &WSMessage{
		Event:     EventAgentOnline,
		Data:      map[string]any{
			"agent_id":   agentID,
			"account_id": accountID,
		},
		AccountID: accountID,
	}

	if err := p.relay.PublishAccount(ctx, accountID, msg); err != nil {
		logger.L().Warnf("ws presence: failed to broadcast agent online: %v", err)
	}

	logger.L().Debugf("ws presence: agent %d online for account %d", agentID, accountID)
	return nil
}

// SetAgentOffline removes an agent from the online set and broadcasts offline event.
//
// Reference: Chatwoot OnlineStatusTracker.set_agent_offline — removes
// from Redis sorted set and hash on disconnect or heartbeat timeout.
func (p *PresenceTracker) SetAgentOffline(ctx context.Context, agentID, accountID uint) error {
	member := presenceMember(agentID, accountID)

	// Remove from sorted set
	if err := p.rdb.ZRem(ctx, RedisKeyPresenceAgents, member).Err(); err != nil {
		return fmt.Errorf("failed to remove agent from sorted set: %w", err)
	}

	// Remove status from hash
	if err := p.rdb.HDel(ctx, RedisKeyPresenceStatus, member).Err(); err != nil {
		return fmt.Errorf("failed to remove agent status: %w", err)
	}

	// Broadcast offline event
	msg := &WSMessage{
		Event:     EventAgentOffline,
		Data:      map[string]any{
			"agent_id":   agentID,
			"account_id": accountID,
		},
		AccountID: accountID,
	}

	if err := p.relay.PublishAccount(ctx, accountID, msg); err != nil {
		logger.L().Warnf("ws presence: failed to broadcast agent offline: %v", err)
	}

	logger.L().Debugf("ws presence: agent %d offline for account %d", agentID, accountID)
	return nil
}

// SetAgentBusy marks an agent as busy (visible but not accepting new conversations).
func (p *PresenceTracker) SetAgentBusy(ctx context.Context, agentID, accountID uint) error {
	member := presenceMember(agentID, accountID)
	now := float64(time.Now().Unix())

	// Keep in sorted set (still "present") but mark as busy in hash
	if err := p.rdb.ZAdd(ctx, RedisKeyPresenceAgents, redis.Z{
		Score:  now,
		Member: member,
	}).Err(); err != nil {
		return fmt.Errorf("failed to set agent busy in sorted set: %w", err)
	}

	if err := p.rdb.HSet(ctx, RedisKeyPresenceStatus, member, "busy").Err(); err != nil {
		return fmt.Errorf("failed to set agent status busy: %w", err)
	}

	// Broadcast presence update
	msg := &WSMessage{
		Event:     EventPresenceUpdate,
		Data:      map[string]any{
			"agent_id":   agentID,
			"account_id": accountID,
			"status":     "busy",
		},
		AccountID: accountID,
	}

	if err := p.relay.PublishAccount(ctx, accountID, msg); err != nil {
		logger.L().Warnf("ws presence: failed to broadcast agent busy: %v", err)
	}

	return nil
}

// SetContactOnline marks a contact as online for a given account/inbox.
// Uses longer TTL than agents (90s vs 20s) per Chatwoot convention.
func (p *PresenceTracker) SetContactOnline(ctx context.Context, contactID, accountID uint) error {
	member := presenceMember(contactID, accountID)
	now := float64(time.Now().Unix())

	if err := p.rdb.ZAdd(ctx, RedisKeyPresenceContacts, redis.Z{
		Score:  now,
		Member: member,
	}).Err(); err != nil {
		return fmt.Errorf("failed to set contact online: %w", err)
	}

	if err := p.rdb.HSet(ctx, RedisKeyPresenceStatus, member, "online").Err(); err != nil {
		return fmt.Errorf("failed to set contact status: %w", err)
	}

	logger.L().Debugf("ws presence: contact %d online for account %d", contactID, accountID)
	return nil
}

// SetContactOffline removes a contact from the online set.
func (p *PresenceTracker) SetContactOffline(ctx context.Context, contactID, accountID uint) error {
	member := presenceMember(contactID, accountID)

	if err := p.rdb.ZRem(ctx, RedisKeyPresenceContacts, member).Err(); err != nil {
		return fmt.Errorf("failed to remove contact from sorted set: %w", err)
	}

	if err := p.rdb.HDel(ctx, RedisKeyPresenceStatus, member).Err(); err != nil {
		return fmt.Errorf("failed to remove contact status: %w", err)
	}

	logger.L().Debugf("ws presence: contact %d offline for account %d", contactID, accountID)
	return nil
}

// GetOnlineAgentsForAccount returns all currently online agent IDs for an account.
// Only returns agents whose sorted-set score is within PresenceDurationAgentSec
// of the current time (i.e., have sent a heartbeat recently).
//
// Reference: Chatwoot OnlineStatusTracker.get_online_agents — queries
// Redis sorted set, filtering by timestamp threshold.
func (p *PresenceTracker) GetOnlineAgentsForAccount(ctx context.Context, accountID uint) ([]uint, error) {
	// Calculate the minimum timestamp threshold
	minScore := float64(time.Now().Unix() - PresenceDurationAgentSec)

	// Get all members with score >= minScore
	results, err := p.rdb.ZRangeByScore(ctx, RedisKeyPresenceAgents, &redis.ZRangeBy{
		Min: fmt.Sprintf("%f", minScore),
		Max: "+inf",
	}).Result()
	if err != nil {
		return nil, fmt.Errorf("failed to query online agents: %w", err)
	}

	// Filter by account prefix and extract IDs
	var agentIDs []uint
	for _, member := range results {
		id, acct := parsePresenceMember(member)
		if acct == accountID {
			agentIDs = append(agentIDs, id)
		}
	}

	return agentIDs, nil
}

// GetAgentStatus returns the current status string for an agent (online/busy/offline).
func (p *PresenceTracker) GetAgentStatus(ctx context.Context, agentID, accountID uint) (string, error) {
	member := presenceMember(agentID, accountID)
	status, err := p.rdb.HGet(ctx, RedisKeyPresenceStatus, member).Result()
	if err != nil {
		if err == redis.Nil {
			return "offline", nil
		}
		return "", fmt.Errorf("failed to get agent status: %w", err)
	}
	return status, nil
}

// CleanupExpired removes stale presence entries whose timestamp score
// has fallen below the expiry threshold. Should be called periodically
// (e.g., every 30 seconds) via a background goroutine.
//
// Reference: Chatwoot OnlineStatusTracker.cleanup — periodically removes
// expired entries from Redis sorted sets.
func (p *PresenceTracker) CleanupExpired(ctx context.Context) error {
	agentThreshold := float64(time.Now().Unix() - PresenceDurationAgentSec)
	contactThreshold := float64(time.Now().Unix() - PresenceDurationContactSec)

	// Remove expired agents
	removedAgents, err := p.rdb.ZRemRangeByScore(ctx, RedisKeyPresenceAgents,
		"0", fmt.Sprintf("%f", agentThreshold)).Result()
	if err != nil {
		logger.L().Warnf("ws presence: failed to cleanup expired agents: %v", err)
	}

	// Remove expired contacts
	removedContacts, err := p.rdb.ZRemRangeByScore(ctx, RedisKeyPresenceContacts,
		"0", fmt.Sprintf("%f", contactThreshold)).Result()
	if err != nil {
		logger.L().Warnf("ws presence: failed to cleanup expired contacts: %v", err)
	}

	if removedAgents > 0 || removedContacts > 0 {
		logger.L().Infof("ws presence: cleanup removed %d agents, %d contacts",
			removedAgents, removedContacts)
	}
	return nil
}

// RefreshAgentPresence refreshes an agent's timestamp in the sorted set.
// Called on each heartbeat to prevent the agent from being cleaned up.
func (p *PresenceTracker) RefreshAgentPresence(ctx context.Context, agentID, accountID uint) error {
	member := presenceMember(agentID, accountID)
	now := float64(time.Now().Unix())

	if err := p.rdb.ZAdd(ctx, RedisKeyPresenceAgents, redis.Z{
		Score:  now,
		Member: member,
	}).Err(); err != nil {
		return fmt.Errorf("failed to refresh agent presence: %w", err)
	}
	return nil
}

// RefreshContactPresence refreshes a contact's timestamp in the sorted set.
func (p *PresenceTracker) RefreshContactPresence(ctx context.Context, contactID, accountID uint) error {
	member := presenceMember(contactID, accountID)
	now := float64(time.Now().Unix())

	if err := p.rdb.ZAdd(ctx, RedisKeyPresenceContacts, redis.Z{
		Score:  now,
		Member: member,
	}).Err(); err != nil {
		return fmt.Errorf("failed to refresh contact presence: %w", err)
	}
	return nil
}

// --- Internal helpers ---

// presenceMember creates a Redis sorted set member string from ID and account ID.
// Format: "{id}:{account_id}" — e.g., "42:1" means user 42 in account 1.
func presenceMember(id, accountID uint) string {
	return fmt.Sprintf("%d:%d", id, accountID)
}

// parsePresenceMember splits a Redis sorted set member string back into id and accountID.
func parsePresenceMember(member string) (uint, uint) {
	parts := strings.SplitN(member, ":", 2)
	if len(parts) != 2 {
		return 0, 0
	}
	id, _ := strconv.ParseUint(parts[0], 10, 32)
	acct, _ := strconv.ParseUint(parts[1], 10, 32)
	return uint(id), uint(acct)
}