// Package redis provides a Redis-based queue implementation
package redis

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/jfraeys/fetch_ml/internal/domain"
	"github.com/redis/go-redis/v9"
)

// Queue implements a Redis-based task queue
type Queue struct {
	client      *redis.Client
	ctx         context.Context
	cancel      context.CancelFunc
	metricsCh   chan metricEvent
	metricsDone chan struct{}
	flushEvery  time.Duration
}

type metricEvent struct {
	JobName string
	Metric  string
	Value   float64
}

// Config holds configuration for Queue
type Config struct {
	RedisAddr            string
	RedisPassword        string
	RedisDB              int
	MetricsFlushInterval time.Duration
}

// NewQueue creates a new Redis queue instance
func NewQueue(cfg Config) (*Queue, error) {
	var opts *redis.Options
	var err error

	if len(cfg.RedisAddr) > 8 && cfg.RedisAddr[:8] == "redis://" {
		opts, err = redis.ParseURL(cfg.RedisAddr)
		if err != nil {
			return nil, fmt.Errorf("invalid redis url: %w", err)
		}
	} else {
		opts = &redis.Options{
			Addr:         cfg.RedisAddr,
			Password:     cfg.RedisPassword,
			DB:           cfg.RedisDB,
			PoolSize:     50,
			MinIdleConns: 10,
			MaxRetries:   3,
			DialTimeout:  5 * time.Second,
			ReadTimeout:  3 * time.Second,
		}
	}

	client := redis.NewClient(opts)

	ctx, cancel := context.WithCancel(context.Background())

	// Test connection
	if err := client.Ping(ctx).Err(); err != nil {
		cancel()
		return nil, fmt.Errorf("failed to connect to redis: %w", err)
	}

	flushEvery := cfg.MetricsFlushInterval
	if flushEvery == 0 {
		flushEvery = 500 * time.Millisecond
	}

	q := &Queue{
		client:      client,
		ctx:         ctx,
		cancel:      cancel,
		metricsCh:   make(chan metricEvent, 100),
		metricsDone: make(chan struct{}),
		flushEvery:  flushEvery,
	}

	go q.metricsFlusher()

	return q, nil
}

// Close closes the queue
func (q *Queue) Close() error {
	q.cancel()
	close(q.metricsCh)
	<-q.metricsDone
	return q.client.Close()
}

// AddTask adds a task to the queue
func (q *Queue) AddTask(task *domain.Task) error {
	if task == nil {
		return errors.New("task is nil")
	}
	if task.ID == "" {
		return errors.New("task ID is required")
	}

	data, err := json.Marshal(task)
	if err != nil {
		return fmt.Errorf("failed to marshal task: %w", err)
	}

	// Add to task hash and queue
	pipe := q.client.Pipeline()
	pipe.HSet(q.ctx, "ml:task:"+task.ID, "data", data)
	pipe.LPush(q.ctx, "ml:queue", task.ID)
	_, err = pipe.Exec(q.ctx)
	if err != nil {
		return fmt.Errorf("failed to add task: %w", err)
	}

	return nil
}

// GetTask retrieves a task by ID
func (q *Queue) GetTask(id string) (*domain.Task, error) {
	if id == "" {
		return nil, errors.New("task ID is required")
	}

	data, err := q.client.HGet(q.ctx, "ml:task:"+id, "data").Bytes()
	if err == redis.Nil {
		return nil, fmt.Errorf("task not found: %s", id)
	}
	if err != nil {
		return nil, fmt.Errorf("failed to get task: %w", err)
	}

	var task domain.Task
	if err := json.Unmarshal(data, &task); err != nil {
		return nil, fmt.Errorf("failed to unmarshal task: %w", err)
	}

	return &task, nil
}

// ListTasks lists all tasks in the queue
func (q *Queue) ListTasks() ([]*domain.Task, error) {
	// Get all task IDs from the queue
	ids, err := q.client.LRange(q.ctx, "ml:queue", 0, -1).Result()
	if err != nil {
		return nil, fmt.Errorf("failed to list tasks: %w", err)
	}

	var tasks []*domain.Task
	for _, id := range ids {
		task, err := q.GetTask(id)
		if err != nil {
			continue
		}
		tasks = append(tasks, task)
	}

	return tasks, nil
}

// CancelTask cancels a task
func (q *Queue) CancelTask(id string) error {
	if id == "" {
		return errors.New("task ID is required")
	}

	// Remove from queue and mark as cancelled
	pipe := q.client.Pipeline()
	pipe.LRem(q.ctx, "ml:queue", 0, id)
	pipe.HSet(q.ctx, "ml:task:"+id, "status", "cancelled")
	_, err := pipe.Exec(q.ctx)
	if err != nil {
		return fmt.Errorf("failed to cancel task: %w", err)
	}

	return nil
}

// UpdateTask updates a task
func (q *Queue) UpdateTask(task *domain.Task) error {
	if task == nil || task.ID == "" {
		return errors.New("task is nil or missing ID")
	}

	data, err := json.Marshal(task)
	if err != nil {
		return fmt.Errorf("failed to marshal task: %w", err)
	}

	if err := q.client.HSet(q.ctx, "ml:task:"+task.ID, "data", data).Err(); err != nil {
		return fmt.Errorf("failed to update task: %w", err)
	}

	return nil
}

// metricsFlusher periodically flushes metrics
func (q *Queue) metricsFlusher() {
	ticker := time.NewTicker(q.flushEvery)
	defer ticker.Stop()

	metrics := make(map[string]map[string]float64)

	for {
		select {
		case <-q.ctx.Done():
			close(q.metricsDone)
			return
		case evt := <-q.metricsCh:
			if metrics[evt.JobName] == nil {
				metrics[evt.JobName] = make(map[string]float64)
			}
			metrics[evt.JobName][evt.Metric] = evt.Value
		case <-ticker.C:
			// Flush metrics to Redis or other backend
			metrics = make(map[string]map[string]float64)
		}
	}
}