package storage

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"strings"
	"time"

	_ "github.com/lib/pq"
	_ "github.com/mattn/go-sqlite3"
)

type DBConfig struct {
	Type       string
	Connection string
	Host       string
	Port       int
	Username   string
	Password   string
	Database   string
}

type DB struct {
	conn   *sql.DB
	dbType string
}

func NewDB(config DBConfig) (*DB, error) {
	var conn *sql.DB
	var err error

	switch strings.ToLower(config.Type) {
	case "sqlite":
		conn, err = sql.Open("sqlite3", config.Connection)
		if err != nil {
			return nil, fmt.Errorf("failed to open SQLite database: %w", err)
		}
		// Enable foreign keys
		if _, err := conn.Exec("PRAGMA foreign_keys = ON"); err != nil {
			return nil, fmt.Errorf("failed to enable foreign keys: %w", err)
		}
		// Enable WAL mode for better concurrency
		if _, err := conn.Exec("PRAGMA journal_mode = WAL"); err != nil {
			return nil, fmt.Errorf("failed to enable WAL mode: %w", err)
		}
	case "postgres":
		connStr := buildPostgresConnectionString(config)
		conn, err = sql.Open("postgres", connStr)
		if err != nil {
			return nil, fmt.Errorf("failed to open PostgreSQL database: %w", err)
		}
	case "postgresql":
		// Handle "postgresql" as alias for "postgres"
		connStr := buildPostgresConnectionString(config)
		conn, err = sql.Open("postgres", connStr)
		if err != nil {
			return nil, fmt.Errorf("failed to open PostgreSQL database: %w", err)
		}
	default:
		return nil, fmt.Errorf("unsupported database type: %s", config.Type)
	}

	return &DB{conn: conn, dbType: strings.ToLower(config.Type)}, nil
}

func buildPostgresConnectionString(config DBConfig) string {
	if config.Connection != "" {
		return config.Connection
	}

	var connStr strings.Builder
	connStr.WriteString("host=")
	if config.Host != "" {
		connStr.WriteString(config.Host)
	} else {
		connStr.WriteString("localhost")
	}

	if config.Port > 0 {
		connStr.WriteString(fmt.Sprintf(" port=%d", config.Port))
	} else {
		connStr.WriteString(" port=5432")
	}

	if config.Username != "" {
		connStr.WriteString(fmt.Sprintf(" user=%s", config.Username))
	}

	if config.Password != "" {
		connStr.WriteString(fmt.Sprintf(" password=%s", config.Password))
	}

	if config.Database != "" {
		connStr.WriteString(fmt.Sprintf(" dbname=%s", config.Database))
	} else {
		connStr.WriteString(" dbname=fetch_ml")
	}

	connStr.WriteString(" sslmode=disable")
	return connStr.String()
}

// Legacy constructor for backward compatibility
func NewDBFromPath(dbPath string) (*DB, error) {
	return NewDB(DBConfig{
		Type:       "sqlite",
		Connection: dbPath,
	})
}

type Job struct {
	ID        string            `json:"id"`
	JobName   string            `json:"job_name"`
	Args      string            `json:"args"`
	Status    string            `json:"status"`
	Priority  int64             `json:"priority"`
	CreatedAt time.Time         `json:"created_at"`
	StartedAt *time.Time        `json:"started_at,omitempty"`
	EndedAt   *time.Time        `json:"ended_at,omitempty"`
	WorkerID  string            `json:"worker_id,omitempty"`
	Error     string            `json:"error,omitempty"`
	Datasets  []string          `json:"datasets,omitempty"`
	Metadata  map[string]string `json:"metadata,omitempty"`
	UpdatedAt time.Time         `json:"updated_at"`
}

type Worker struct {
	ID            string            `json:"id"`
	Hostname      string            `json:"hostname"`
	LastHeartbeat time.Time         `json:"last_heartbeat"`
	Status        string            `json:"status"`
	CurrentJobs   int               `json:"current_jobs"`
	MaxJobs       int               `json:"max_jobs"`
	Metadata      map[string]string `json:"metadata,omitempty"`
}

func (db *DB) Initialize(schema string) error {
	if _, err := db.conn.Exec(schema); err != nil {
		return fmt.Errorf("failed to initialize database: %w", err)
	}
	return nil
}

func (db *DB) Close() error {
	return db.conn.Close()
}

// Job operations
func (db *DB) CreateJob(job *Job) error {
	datasetsJSON, _ := json.Marshal(job.Datasets)
	metadataJSON, _ := json.Marshal(job.Metadata)

	var query string
	if db.dbType == "sqlite" {
		query = `INSERT INTO jobs (id, job_name, args, status, priority, datasets, metadata)
		          VALUES (?, ?, ?, ?, ?, ?, ?)`
	} else {
		query = `INSERT INTO jobs (id, job_name, args, status, priority, datasets, metadata)
		          VALUES ($1, $2, $3, $4, $5, $6, $7)`
	}

	_, err := db.conn.Exec(query, job.ID, job.JobName, job.Args, job.Status,
		job.Priority, string(datasetsJSON), string(metadataJSON))
	if err != nil {
		return fmt.Errorf("failed to create job: %w", err)
	}
	return nil
}

func (db *DB) GetJob(id string) (*Job, error) {
	var query string
	if db.dbType == "sqlite" {
		query = `SELECT id, job_name, args, status, priority, created_at, started_at, 
		                 ended_at, worker_id, error, datasets, metadata, updated_at
		          FROM jobs WHERE id = ?`
	} else {
		query = `SELECT id, job_name, args, status, priority, created_at, started_at, 
		                 ended_at, worker_id, error, datasets, metadata, updated_at
		          FROM jobs WHERE id = $1`
	}

	var job Job
	var datasetsJSON, metadataJSON string
	var workerID sql.NullString
	var errorMsg sql.NullString

	err := db.conn.QueryRow(query, id).Scan(
		&job.ID, &job.JobName, &job.Args, &job.Status, &job.Priority,
		&job.CreatedAt, &job.StartedAt, &job.EndedAt, &workerID,
		&errorMsg, &datasetsJSON, &metadataJSON, &job.UpdatedAt)

	if err != nil {
		return nil, fmt.Errorf("failed to get job: %w", err)
	}

	if workerID.Valid {
		job.WorkerID = workerID.String
	}

	if errorMsg.Valid {
		job.Error = errorMsg.String
	}

	json.Unmarshal([]byte(datasetsJSON), &job.Datasets)
	json.Unmarshal([]byte(metadataJSON), &job.Metadata)

	return &job, nil
}

func (db *DB) UpdateJobStatus(id, status, workerID, errorMsg string) error {
	var query string
	if db.dbType == "sqlite" {
		query = `UPDATE jobs SET status = ?, worker_id = ?, error = ?, 
		                 started_at = CASE WHEN ? = 'running' AND started_at IS NULL THEN CURRENT_TIMESTAMP ELSE started_at END,
		                 ended_at = CASE WHEN ? IN ('completed', 'failed') AND ended_at IS NULL THEN CURRENT_TIMESTAMP ELSE ended_at END
		          WHERE id = ?`
	} else {
		query = `UPDATE jobs SET status = $1, worker_id = $2, error = $3, 
		                 started_at = CASE WHEN $4 = 'running' AND started_at IS NULL THEN CURRENT_TIMESTAMP ELSE started_at END,
		                 ended_at = CASE WHEN $5 IN ('completed', 'failed') AND ended_at IS NULL THEN CURRENT_TIMESTAMP ELSE ended_at END
		          WHERE id = $6`
	}

	_, err := db.conn.Exec(query, status, workerID, errorMsg, status, status, id)
	if err != nil {
		return fmt.Errorf("failed to update job status: %w", err)
	}
	return nil
}

func (db *DB) ListJobs(status string, limit int) ([]*Job, error) {
	var query string
	if db.dbType == "sqlite" {
		query = `SELECT id, job_name, args, status, priority, created_at, started_at, 
	                 ended_at, worker_id, error, datasets, metadata, updated_at
	          FROM jobs`
	} else {
		query = `SELECT id, job_name, args, status, priority, created_at, started_at, 
	                 ended_at, worker_id, error, datasets, metadata, updated_at
	          FROM jobs`
	}

	var args []interface{}
	if status != "" {
		if db.dbType == "sqlite" {
			query += " WHERE status = ?"
		} else {
			query += " WHERE status = $1"
		}
		args = append(args, status)
	}
	query += " ORDER BY created_at DESC"
	if limit > 0 {
		if db.dbType == "sqlite" {
			query += " LIMIT ?"
		} else {
			query += fmt.Sprintf(" LIMIT $%d", len(args)+1)
		}
		args = append(args, limit)
	}

	rows, err := db.conn.Query(query, args...)
	if err != nil {
		return nil, fmt.Errorf("failed to list jobs: %w", err)
	}
	defer rows.Close()

	var jobs []*Job
	for rows.Next() {
		var job Job
		var datasetsJSON, metadataJSON string
		var workerID sql.NullString
		var errorMsg sql.NullString

		err := rows.Scan(&job.ID, &job.JobName, &job.Args, &job.Status, &job.Priority,
			&job.CreatedAt, &job.StartedAt, &job.EndedAt, &workerID,
			&errorMsg, &datasetsJSON, &metadataJSON, &job.UpdatedAt)
		if err != nil {
			return nil, fmt.Errorf("failed to scan job: %w", err)
		}

		if workerID.Valid {
			job.WorkerID = workerID.String
		}

		if errorMsg.Valid {
			job.Error = errorMsg.String
		}

		json.Unmarshal([]byte(datasetsJSON), &job.Datasets)
		json.Unmarshal([]byte(metadataJSON), &job.Metadata)

		jobs = append(jobs, &job)
	}

	return jobs, nil
}

// Worker operations
func (db *DB) RegisterWorker(worker *Worker) error {
	metadataJSON, _ := json.Marshal(worker.Metadata)

	var query string
	if db.dbType == "sqlite" {
		query = `INSERT OR REPLACE INTO workers (id, hostname, status, current_jobs, max_jobs, metadata)
		          VALUES (?, ?, ?, ?, ?, ?)`
	} else {
		query = `INSERT INTO workers (id, hostname, status, current_jobs, max_jobs, metadata)
		          VALUES ($1, $2, $3, $4, $5, $6)
		          ON CONFLICT (id) DO UPDATE SET
		          hostname = EXCLUDED.hostname,
		          status = EXCLUDED.status,
		          current_jobs = EXCLUDED.current_jobs,
		          max_jobs = EXCLUDED.max_jobs,
		          metadata = EXCLUDED.metadata`
	}

	_, err := db.conn.Exec(query, worker.ID, worker.Hostname, worker.Status,
		worker.CurrentJobs, worker.MaxJobs, string(metadataJSON))
	if err != nil {
		return fmt.Errorf("failed to register worker: %w", err)
	}
	return nil
}

func (db *DB) UpdateWorkerHeartbeat(workerID string) error {
	var query string
	if db.dbType == "sqlite" {
		query = `UPDATE workers SET last_heartbeat = CURRENT_TIMESTAMP WHERE id = ?`
	} else {
		query = `UPDATE workers SET last_heartbeat = CURRENT_TIMESTAMP WHERE id = $1`
	}

	_, err := db.conn.Exec(query, workerID)
	if err != nil {
		return fmt.Errorf("failed to update worker heartbeat: %w", err)
	}
	return nil
}

func (db *DB) GetActiveWorkers() ([]*Worker, error) {
	var query string
	if db.dbType == "sqlite" {
		query = `SELECT id, hostname, last_heartbeat, status, current_jobs, max_jobs, metadata
		          FROM workers WHERE status = 'active' AND last_heartbeat > datetime('now', '-30 seconds')`
	} else {
		query = `SELECT id, hostname, last_heartbeat, status, current_jobs, max_jobs, metadata
		          FROM workers WHERE status = 'active' AND last_heartbeat > NOW() - INTERVAL '30 seconds'`
	}

	rows, err := db.conn.Query(query)
	if err != nil {
		return nil, fmt.Errorf("failed to get active workers: %w", err)
	}
	defer rows.Close()

	var workers []*Worker
	for rows.Next() {
		var worker Worker
		var metadataJSON string

		err := rows.Scan(&worker.ID, &worker.Hostname, &worker.LastHeartbeat,
			&worker.Status, &worker.CurrentJobs, &worker.MaxJobs, &metadataJSON)
		if err != nil {
			return nil, fmt.Errorf("failed to scan worker: %w", err)
		}

		json.Unmarshal([]byte(metadataJSON), &worker.Metadata)
		workers = append(workers, &worker)
	}

	return workers, nil
}

// Metrics operations
func (db *DB) RecordJobMetric(jobID, metricName, metricValue string) error {
	var query string
	if db.dbType == "sqlite" {
		query = `INSERT INTO job_metrics (job_id, metric_name, metric_value) VALUES (?, ?, ?)`
	} else {
		query = `INSERT INTO job_metrics (job_id, metric_name, metric_value) VALUES ($1, $2, $3)`
	}

	_, err := db.conn.Exec(query, jobID, metricName, metricValue)
	if err != nil {
		return fmt.Errorf("failed to record job metric: %w", err)
	}
	return nil
}

func (db *DB) RecordSystemMetric(metricName, metricValue string) error {
	var query string
	if db.dbType == "sqlite" {
		query = `INSERT INTO system_metrics (metric_name, metric_value) VALUES (?, ?)`
	} else {
		query = `INSERT INTO system_metrics (metric_name, metric_value) VALUES ($1, $2)`
	}

	_, err := db.conn.Exec(query, metricName, metricValue)
	if err != nil {
		return fmt.Errorf("failed to record system metric: %w", err)
	}
	return nil
}

func (db *DB) GetJobMetrics(jobID string) (map[string]string, error) {
	var query string
	if db.dbType == "sqlite" {
		query = `SELECT metric_name, metric_value FROM job_metrics 
		          WHERE job_id = ? ORDER BY timestamp DESC`
	} else {
		query = `SELECT metric_name, metric_value FROM job_metrics 
		          WHERE job_id = $1 ORDER BY timestamp DESC`
	}

	rows, err := db.conn.Query(query, jobID)
	if err != nil {
		return nil, fmt.Errorf("failed to get job metrics: %w", err)
	}
	defer rows.Close()

	metrics := make(map[string]string)
	for rows.Next() {
		var name, value string
		if err := rows.Scan(&name, &value); err != nil {
			return nil, fmt.Errorf("failed to scan metric: %w", err)
		}
		metrics[name] = value
	}

	return metrics, nil
}