// Package postgres provides PostgreSQL-based implementations of port interfaces.
package postgres

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"time"

	"github.com/orchard9/rdev/internal/domain"
	"github.com/orchard9/rdev/internal/port"
)

// CommandQueueRepository implements port.CommandQueue using PostgreSQL.
type CommandQueueRepository struct {
	db *sql.DB
}

// NewCommandQueueRepository creates a new PostgreSQL command queue repository.
func NewCommandQueueRepository(db *sql.DB) *CommandQueueRepository {
	return &CommandQueueRepository{db: db}
}

// Ensure CommandQueueRepository implements port.CommandQueue at compile time.
var _ port.CommandQueue = (*CommandQueueRepository)(nil)

// Enqueue adds a command to the queue.
func (r *CommandQueueRepository) Enqueue(ctx context.Context, cmd *domain.QueuedCommand) error {
	var id string
	err := r.db.QueryRowContext(ctx, `
		INSERT INTO command_queue (project_id, command, command_type, working_dir, status, priority, api_key_id)
		VALUES ($1, $2, $3, $4, $5, $6, $7)
		RETURNING id, created_at
	`, cmd.ProjectID, cmd.Command, string(cmd.CommandType), nullString(cmd.WorkingDir),
		string(cmd.Status), cmd.Priority, nullString(cmd.APIKeyID)).Scan(&id, &cmd.CreatedAt)

	if err != nil {
		return fmt.Errorf("enqueue command: %w", err)
	}

	cmd.ID = domain.QueuedCommandID(id)
	return nil
}

// Dequeue retrieves and locks the next pending command for a project.
// Uses FOR UPDATE SKIP LOCKED for safe concurrent access.
func (r *CommandQueueRepository) Dequeue(ctx context.Context, projectID string) (*domain.QueuedCommand, error) {
	// Use a transaction to atomically select and update
	tx, err := r.db.BeginTx(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("begin transaction: %w", err)
	}
	defer func() { _ = tx.Rollback() }()

	var cmd domain.QueuedCommand
	var id string
	var commandType string
	var status string
	var workingDir sql.NullString
	var apiKeyID sql.NullString

	// Select the highest priority pending command and lock it
	err = tx.QueryRowContext(ctx, `
		SELECT id, project_id, command, command_type, working_dir, status, priority, created_at, api_key_id
		FROM command_queue
		WHERE project_id = $1 AND status = 'pending'
		ORDER BY priority DESC, created_at ASC
		LIMIT 1
		FOR UPDATE SKIP LOCKED
	`, projectID).Scan(
		&id,
		&cmd.ProjectID,
		&cmd.Command,
		&commandType,
		&workingDir,
		&status,
		&cmd.Priority,
		&cmd.CreatedAt,
		&apiKeyID,
	)

	if errors.Is(err, sql.ErrNoRows) {
		return nil, nil // No pending commands
	}
	if err != nil {
		return nil, fmt.Errorf("select pending command: %w", err)
	}

	cmd.ID = domain.QueuedCommandID(id)
	cmd.CommandType = domain.CommandType(commandType)
	cmd.Status = domain.QueueStatus(status)
	if workingDir.Valid {
		cmd.WorkingDir = workingDir.String
	}
	if apiKeyID.Valid {
		cmd.APIKeyID = apiKeyID.String
	}

	// Update status to running
	now := time.Now()
	_, err = tx.ExecContext(ctx, `
		UPDATE command_queue
		SET status = 'running', started_at = $1
		WHERE id = $2
	`, now, id)
	if err != nil {
		return nil, fmt.Errorf("update to running: %w", err)
	}

	if err := tx.Commit(); err != nil {
		return nil, fmt.Errorf("commit transaction: %w", err)
	}

	cmd.Status = domain.QueueStatusRunning
	cmd.StartedAt = &now
	return &cmd, nil
}

// UpdateStatus updates the status of a queued command.
func (r *CommandQueueRepository) UpdateStatus(ctx context.Context, cmdID domain.QueuedCommandID, status domain.QueueStatus, result *domain.QueuedCommandResult) error {
	var err error

	if result != nil {
		now := time.Now()
		_, err = r.db.ExecContext(ctx, `
			UPDATE command_queue
			SET status = $1, completed_at = $2, result_exit_code = $3, result_output = $4, result_error = $5
			WHERE id = $6
		`, string(status), now, result.ExitCode, nullString(result.Output), nullString(result.Error), string(cmdID))
	} else {
		_, err = r.db.ExecContext(ctx, `
			UPDATE command_queue
			SET status = $1
			WHERE id = $2
		`, string(status), string(cmdID))
	}

	if err != nil {
		return fmt.Errorf("update status: %w", err)
	}
	return nil
}

// GetByID retrieves a specific queued command by ID.
func (r *CommandQueueRepository) GetByID(ctx context.Context, cmdID domain.QueuedCommandID) (*domain.QueuedCommand, error) {
	var cmd domain.QueuedCommand
	var id string
	var commandType string
	var status string
	var workingDir sql.NullString
	var startedAt sql.NullTime
	var completedAt sql.NullTime
	var exitCode sql.NullInt32
	var output sql.NullString
	var resultError sql.NullString
	var apiKeyID sql.NullString

	err := r.db.QueryRowContext(ctx, `
		SELECT id, project_id, command, command_type, working_dir, status, priority,
		       created_at, started_at, completed_at, result_exit_code, result_output, result_error, api_key_id
		FROM command_queue
		WHERE id = $1
	`, string(cmdID)).Scan(
		&id,
		&cmd.ProjectID,
		&cmd.Command,
		&commandType,
		&workingDir,
		&status,
		&cmd.Priority,
		&cmd.CreatedAt,
		&startedAt,
		&completedAt,
		&exitCode,
		&output,
		&resultError,
		&apiKeyID,
	)

	if errors.Is(err, sql.ErrNoRows) {
		return nil, domain.ErrCommandNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("get command: %w", err)
	}

	cmd.ID = domain.QueuedCommandID(id)
	cmd.CommandType = domain.CommandType(commandType)
	cmd.Status = domain.QueueStatus(status)

	if workingDir.Valid {
		cmd.WorkingDir = workingDir.String
	}
	if startedAt.Valid {
		cmd.StartedAt = &startedAt.Time
	}
	if completedAt.Valid {
		cmd.CompletedAt = &completedAt.Time
	}
	if exitCode.Valid {
		ec := int(exitCode.Int32)
		cmd.ExitCode = &ec
	}
	if output.Valid {
		cmd.Output = output.String
	}
	if resultError.Valid {
		cmd.Error = resultError.String
	}
	if apiKeyID.Valid {
		cmd.APIKeyID = apiKeyID.String
	}

	return &cmd, nil
}

// List returns queued commands for a project with optional filters.
func (r *CommandQueueRepository) List(ctx context.Context, projectID string, filters *domain.QueueFilters) ([]*domain.QueuedCommand, error) {
	if filters == nil {
		filters = domain.DefaultQueueFilters()
	}

	// Build query with optional filters
	query := `
		SELECT id, project_id, command, command_type, working_dir, status, priority,
		       created_at, started_at, completed_at, result_exit_code, result_output, result_error, api_key_id
		FROM command_queue
		WHERE project_id = $1
	`
	args := []any{projectID}
	argNum := 2

	if filters.Status != nil {
		query += fmt.Sprintf(" AND status = $%d", argNum)
		args = append(args, string(*filters.Status))
		argNum++
	}

	// Sort order
	if filters.SortOrder == "asc" {
		query += " ORDER BY created_at ASC"
	} else {
		query += " ORDER BY created_at DESC"
	}

	// Pagination
	query += fmt.Sprintf(" LIMIT $%d OFFSET $%d", argNum, argNum+1)
	args = append(args, filters.Limit, filters.Offset)

	rows, err := r.db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("list commands: %w", err)
	}
	defer func() { _ = rows.Close() }()

	var commands []*domain.QueuedCommand
	for rows.Next() {
		var cmd domain.QueuedCommand
		var id string
		var commandType string
		var status string
		var workingDir sql.NullString
		var startedAt sql.NullTime
		var completedAt sql.NullTime
		var exitCode sql.NullInt32
		var output sql.NullString
		var resultError sql.NullString
		var apiKeyID sql.NullString

		if err := rows.Scan(
			&id,
			&cmd.ProjectID,
			&cmd.Command,
			&commandType,
			&workingDir,
			&status,
			&cmd.Priority,
			&cmd.CreatedAt,
			&startedAt,
			&completedAt,
			&exitCode,
			&output,
			&resultError,
			&apiKeyID,
		); err != nil {
			return nil, fmt.Errorf("scan command: %w", err)
		}

		cmd.ID = domain.QueuedCommandID(id)
		cmd.CommandType = domain.CommandType(commandType)
		cmd.Status = domain.QueueStatus(status)

		if workingDir.Valid {
			cmd.WorkingDir = workingDir.String
		}
		if startedAt.Valid {
			cmd.StartedAt = &startedAt.Time
		}
		if completedAt.Valid {
			cmd.CompletedAt = &completedAt.Time
		}
		if exitCode.Valid {
			ec := int(exitCode.Int32)
			cmd.ExitCode = &ec
		}
		if output.Valid {
			cmd.Output = output.String
		}
		if resultError.Valid {
			cmd.Error = resultError.String
		}
		if apiKeyID.Valid {
			cmd.APIKeyID = apiKeyID.String
		}

		commands = append(commands, &cmd)
	}

	return commands, nil
}

// Cancel marks a pending command as cancelled.
func (r *CommandQueueRepository) Cancel(ctx context.Context, cmdID domain.QueuedCommandID) error {
	result, err := r.db.ExecContext(ctx, `
		UPDATE command_queue
		SET status = 'cancelled', completed_at = NOW()
		WHERE id = $1 AND status = 'pending'
	`, string(cmdID))
	if err != nil {
		return fmt.Errorf("cancel command: %w", err)
	}

	rows, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("rows affected: %w", err)
	}

	if rows == 0 {
		// Check if command exists
		var exists bool
		err := r.db.QueryRowContext(ctx, `SELECT EXISTS(SELECT 1 FROM command_queue WHERE id = $1)`, string(cmdID)).Scan(&exists)
		if err != nil {
			return fmt.Errorf("check exists: %w", err)
		}
		if !exists {
			return domain.ErrCommandNotFound
		}
		// Command exists but not in pending state
		return fmt.Errorf("command is not in pending state")
	}

	return nil
}

// GetStats returns queue statistics for a project (or all projects if empty).
func (r *CommandQueueRepository) GetStats(ctx context.Context, projectID string) (*domain.QueueStats, error) {
	var stats domain.QueueStats

	query := `
		SELECT
			COUNT(*) FILTER (WHERE status = 'pending') as pending,
			COUNT(*) FILTER (WHERE status = 'running') as running,
			COUNT(*) FILTER (WHERE status = 'completed') as completed,
			COUNT(*) FILTER (WHERE status = 'failed') as failed,
			COUNT(*) FILTER (WHERE status = 'cancelled') as cancelled
		FROM command_queue
	`

	var err error
	if projectID != "" {
		query += " WHERE project_id = $1"
		err = r.db.QueryRowContext(ctx, query, projectID).Scan(
			&stats.TotalPending,
			&stats.TotalRunning,
			&stats.TotalCompleted,
			&stats.TotalFailed,
			&stats.TotalCancelled,
		)
	} else {
		err = r.db.QueryRowContext(ctx, query).Scan(
			&stats.TotalPending,
			&stats.TotalRunning,
			&stats.TotalCompleted,
			&stats.TotalFailed,
			&stats.TotalCancelled,
		)
	}

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

	return &stats, nil
}

// CleanupOld removes completed/failed/cancelled commands older than the specified duration.
func (r *CommandQueueRepository) CleanupOld(ctx context.Context, olderThanDays int) (int64, error) {
	result, err := r.db.ExecContext(ctx, `
		DELETE FROM command_queue
		WHERE status IN ('completed', 'failed', 'cancelled')
		AND completed_at < NOW() - INTERVAL '1 day' * $1
	`, olderThanDays)
	if err != nil {
		return 0, fmt.Errorf("cleanup old commands: %w", err)
	}

	return result.RowsAffected()
}

// nullString returns a sql.NullString for optional string fields.
func nullString(s string) sql.NullString {
	if s == "" {
		return sql.NullString{}
	}
	return sql.NullString{String: s, Valid: true}
}