package recognition

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

	"github.com/food-ai/backend/internal/adapters/ai"
	"github.com/jackc/pgx/v5/pgxpool"
)

// JobRepository provides all DB operations on dish_recognition_jobs.
type JobRepository interface {
	InsertJob(ctx context.Context, job *Job) error
	GetJobByID(ctx context.Context, jobID string) (*Job, error)
	UpdateJobStatus(ctx context.Context, jobID, status string, result *ai.DishResult, errMsg *string) error
	QueuePosition(ctx context.Context, userPlan string, createdAt time.Time) (int, error)
	NotifyJobUpdate(ctx context.Context, jobID string) error
	ListTodayUnlinked(ctx context.Context, userID string) ([]*JobSummary, error)
	ListAll(ctx context.Context, userID string) ([]*JobSummary, error)
}

// PostgresJobRepository implements JobRepository using a pgxpool.
type PostgresJobRepository struct {
	pool *pgxpool.Pool
}

// NewJobRepository creates a new PostgresJobRepository.
func NewJobRepository(pool *pgxpool.Pool) *PostgresJobRepository {
	return &PostgresJobRepository{pool: pool}
}

// InsertJob inserts a new recognition job and populates the ID and CreatedAt fields.
func (repository *PostgresJobRepository) InsertJob(queryContext context.Context, job *Job) error {
	return repository.pool.QueryRow(queryContext,
		`INSERT INTO dish_recognition_jobs (user_id, user_plan, image_base64, mime_type, lang, target_date, target_meal_type)
		 VALUES ($1, $2, $3, $4, $5, $6, $7)
		 RETURNING id, created_at`,
		job.UserID, job.UserPlan, job.ImageBase64, job.MimeType, job.Lang, job.TargetDate, job.TargetMealType,
	).Scan(&job.ID, &job.CreatedAt)
}

// GetJobByID fetches a single job by primary key.
func (repository *PostgresJobRepository) GetJobByID(queryContext context.Context, jobID string) (*Job, error) {
	var job Job
	var resultJSON []byte

	queryError := repository.pool.QueryRow(queryContext,
		`SELECT id, user_id, user_plan, image_base64, mime_type, lang,
		        target_date::text, target_meal_type, status,
		        result, error, created_at, started_at, completed_at
		 FROM dish_recognition_jobs WHERE id = $1`,
		jobID,
	).Scan(
		&job.ID, &job.UserID, &job.UserPlan,
		&job.ImageBase64, &job.MimeType, &job.Lang,
		&job.TargetDate, &job.TargetMealType, &job.Status,
		&resultJSON, &job.Error, &job.CreatedAt, &job.StartedAt, &job.CompletedAt,
	)
	if queryError != nil {
		return nil, queryError
	}

	if resultJSON != nil {
		var dishResult ai.DishResult
		if unmarshalError := json.Unmarshal(resultJSON, &dishResult); unmarshalError == nil {
			job.Result = &dishResult
		}
	}

	return &job, nil
}

// UpdateJobStatus transitions a job to a new status and records the result or error.
func (repository *PostgresJobRepository) UpdateJobStatus(
	queryContext context.Context,
	jobID, status string,
	result *ai.DishResult,
	errMsg *string,
) error {
	var resultJSON []byte
	if result != nil {
		marshalledBytes, marshalError := json.Marshal(result)
		if marshalError != nil {
			return marshalError
		}
		resultJSON = marshalledBytes
	}

	switch status {
	case JobStatusProcessing:
		_, updateError := repository.pool.Exec(queryContext,
			`UPDATE dish_recognition_jobs SET status = $1, started_at = now() WHERE id = $2`,
			status, jobID,
		)
		return updateError
	default:
		_, updateError := repository.pool.Exec(queryContext,
			`UPDATE dish_recognition_jobs
			 SET status = $1, result = $2, error = $3, completed_at = now()
			 WHERE id = $4`,
			status, resultJSON, errMsg, jobID,
		)
		return updateError
	}
}

// QueuePosition counts jobs ahead of createdAt in the same plan's queue.
func (repository *PostgresJobRepository) QueuePosition(
	queryContext context.Context,
	userPlan string,
	createdAt time.Time,
) (int, error) {
	var position int
	queryError := repository.pool.QueryRow(queryContext,
		`SELECT COUNT(*) FROM dish_recognition_jobs
		 WHERE status IN ('pending', 'processing')
		   AND user_plan = $1
		   AND created_at < $2`,
		userPlan, createdAt,
	).Scan(&position)
	return position, queryError
}

// NotifyJobUpdate sends a PostgreSQL NOTIFY on the job_update channel.
func (repository *PostgresJobRepository) NotifyJobUpdate(queryContext context.Context, jobID string) error {
	_, notifyError := repository.pool.Exec(queryContext, `SELECT pg_notify('job_update', $1)`, jobID)
	return notifyError
}

// ListAll returns all recognition jobs for the given user, newest first.
func (repository *PostgresJobRepository) ListAll(queryContext context.Context, userID string) ([]*JobSummary, error) {
	rows, queryError := repository.pool.Query(queryContext,
		`SELECT id, status, target_date::text, target_meal_type,
		        result, error, created_at
		 FROM dish_recognition_jobs
		 WHERE user_id = $1
		 ORDER BY created_at DESC`,
		userID,
	)
	if queryError != nil {
		return nil, queryError
	}
	defer rows.Close()

	var summaries []*JobSummary
	for rows.Next() {
		var summary JobSummary
		var resultJSON []byte
		scanError := rows.Scan(
			&summary.ID, &summary.Status, &summary.TargetDate, &summary.TargetMealType,
			&resultJSON, &summary.Error, &summary.CreatedAt,
		)
		if scanError != nil {
			return nil, scanError
		}
		if resultJSON != nil {
			var dishResult ai.DishResult
			if unmarshalError := json.Unmarshal(resultJSON, &dishResult); unmarshalError == nil {
				summary.Result = &dishResult
			}
		}
		summaries = append(summaries, &summary)
	}
	if rowsError := rows.Err(); rowsError != nil {
		return nil, rowsError
	}
	return summaries, nil
}

// ListTodayUnlinked returns today's jobs for the given user that have not yet been
// linked to any meal_diary entry.
func (repository *PostgresJobRepository) ListTodayUnlinked(queryContext context.Context, userID string) ([]*JobSummary, error) {
	rows, queryError := repository.pool.Query(queryContext,
		`SELECT id, status, target_date::text, target_meal_type,
		        result, error, created_at
		 FROM dish_recognition_jobs
		 WHERE user_id = $1
		   AND created_at::date = CURRENT_DATE
		   AND id NOT IN (
		       SELECT job_id FROM meal_diary WHERE job_id IS NOT NULL
		   )
		 ORDER BY created_at DESC`,
		userID,
	)
	if queryError != nil {
		return nil, queryError
	}
	defer rows.Close()

	var summaries []*JobSummary
	for rows.Next() {
		var summary JobSummary
		var resultJSON []byte
		scanError := rows.Scan(
			&summary.ID, &summary.Status, &summary.TargetDate, &summary.TargetMealType,
			&resultJSON, &summary.Error, &summary.CreatedAt,
		)
		if scanError != nil {
			return nil, scanError
		}
		if resultJSON != nil {
			var dishResult ai.DishResult
			if unmarshalError := json.Unmarshal(resultJSON, &dishResult); unmarshalError == nil {
				summary.Result = &dishResult
			}
		}
		summaries = append(summaries, &summary)
	}
	if rowsError := rows.Err(); rowsError != nil {
		return nil, rowsError
	}
	return summaries, nil
}