package db

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

	"github.com/jackc/pgx/v5"
)

// Runner represents a registered compute worker.
type Runner struct {
	ID            string
	Name          string
	TokenHash     string
	TokenPrefix   string
	Tags          []string
	Status        string
	LastHeartbeat *time.Time
	LastJobID     *string
	Metadata      map[string]any
	CreatedAt     time.Time
	UpdatedAt     time.Time
}

// JobDefinitionRecord is a job definition stored in the database.
type JobDefinitionRecord struct {
	ID             string
	Name           string
	Version        int
	TriggerType    string
	ScopeType      string
	ComputeType    string
	RunnerTags     []string
	TimeoutSeconds int
	MaxRetries     int
	Priority       int
	Definition     map[string]any
	Enabled        bool
	CreatedAt      time.Time
	UpdatedAt      time.Time
}

// Job represents a single compute job instance.
type Job struct {
	ID              string
	JobDefinitionID *string
	DefinitionName  string
	Status          string
	Priority        int
	ItemID          *string
	ProjectID       *string
	ScopeMetadata   map[string]any
	RunnerID        *string
	RunnerTags      []string
	CreatedAt       time.Time
	ClaimedAt       *time.Time
	StartedAt       *time.Time
	CompletedAt     *time.Time
	TimeoutSeconds  int
	ExpiresAt       *time.Time
	Progress        int
	ProgressMessage *string
	Result          map[string]any
	ErrorMessage    *string
	RetryCount      int
	MaxRetries      int
	CreatedBy       *string
	CancelledBy     *string
}

// JobLogEntry is a single log line for a job.
type JobLogEntry struct {
	ID        string
	JobID     string
	Timestamp time.Time
	Level     string
	Message   string
	Metadata  map[string]any
}

// JobRepository provides job and runner database operations.
type JobRepository struct {
	db *DB
}

// NewJobRepository creates a new job repository.
func NewJobRepository(db *DB) *JobRepository {
	return &JobRepository{db: db}
}

// ---------------------------------------------------------------------------
// Job Definitions
// ---------------------------------------------------------------------------

// UpsertDefinition inserts or updates a job definition record.
func (r *JobRepository) UpsertDefinition(ctx context.Context, d *JobDefinitionRecord) error {
	defJSON, err := json.Marshal(d.Definition)
	if err != nil {
		return fmt.Errorf("marshaling definition: %w", err)
	}

	err = r.db.pool.QueryRow(ctx, `
		INSERT INTO job_definitions (name, version, trigger_type, scope_type, compute_type,
		                             runner_tags, timeout_seconds, max_retries, priority,
		                             definition, enabled)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
		ON CONFLICT (name) DO UPDATE SET
			version = EXCLUDED.version,
			trigger_type = EXCLUDED.trigger_type,
			scope_type = EXCLUDED.scope_type,
			compute_type = EXCLUDED.compute_type,
			runner_tags = EXCLUDED.runner_tags,
			timeout_seconds = EXCLUDED.timeout_seconds,
			max_retries = EXCLUDED.max_retries,
			priority = EXCLUDED.priority,
			definition = EXCLUDED.definition,
			enabled = EXCLUDED.enabled,
			updated_at = now()
		RETURNING id, created_at, updated_at
	`, d.Name, d.Version, d.TriggerType, d.ScopeType, d.ComputeType,
		d.RunnerTags, d.TimeoutSeconds, d.MaxRetries, d.Priority,
		defJSON, d.Enabled,
	).Scan(&d.ID, &d.CreatedAt, &d.UpdatedAt)
	if err != nil {
		return fmt.Errorf("upserting job definition: %w", err)
	}
	return nil
}

// GetDefinition returns a job definition by name.
func (r *JobRepository) GetDefinition(ctx context.Context, name string) (*JobDefinitionRecord, error) {
	d := &JobDefinitionRecord{}
	var defJSON []byte
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, name, version, trigger_type, scope_type, compute_type,
		       runner_tags, timeout_seconds, max_retries, priority,
		       definition, enabled, created_at, updated_at
		FROM job_definitions WHERE name = $1
	`, name).Scan(
		&d.ID, &d.Name, &d.Version, &d.TriggerType, &d.ScopeType, &d.ComputeType,
		&d.RunnerTags, &d.TimeoutSeconds, &d.MaxRetries, &d.Priority,
		&defJSON, &d.Enabled, &d.CreatedAt, &d.UpdatedAt,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying job definition: %w", err)
	}
	if defJSON != nil {
		if err := json.Unmarshal(defJSON, &d.Definition); err != nil {
			return nil, fmt.Errorf("unmarshaling definition: %w", err)
		}
	}
	return d, nil
}

// ListDefinitions returns all job definitions.
func (r *JobRepository) ListDefinitions(ctx context.Context) ([]*JobDefinitionRecord, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT id, name, version, trigger_type, scope_type, compute_type,
		       runner_tags, timeout_seconds, max_retries, priority,
		       definition, enabled, created_at, updated_at
		FROM job_definitions ORDER BY name
	`)
	if err != nil {
		return nil, fmt.Errorf("querying job definitions: %w", err)
	}
	defer rows.Close()
	return scanJobDefinitions(rows)
}

// GetDefinitionsByTrigger returns all enabled definitions matching a trigger type.
func (r *JobRepository) GetDefinitionsByTrigger(ctx context.Context, triggerType string) ([]*JobDefinitionRecord, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT id, name, version, trigger_type, scope_type, compute_type,
		       runner_tags, timeout_seconds, max_retries, priority,
		       definition, enabled, created_at, updated_at
		FROM job_definitions
		WHERE trigger_type = $1 AND enabled = true
		ORDER BY priority ASC, name
	`, triggerType)
	if err != nil {
		return nil, fmt.Errorf("querying definitions by trigger: %w", err)
	}
	defer rows.Close()
	return scanJobDefinitions(rows)
}

// GetDefinitionByID returns a job definition by ID.
func (r *JobRepository) GetDefinitionByID(ctx context.Context, id string) (*JobDefinitionRecord, error) {
	d := &JobDefinitionRecord{}
	var defJSON []byte
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, name, version, trigger_type, scope_type, compute_type,
		       runner_tags, timeout_seconds, max_retries, priority,
		       definition, enabled, created_at, updated_at
		FROM job_definitions WHERE id = $1
	`, id).Scan(
		&d.ID, &d.Name, &d.Version, &d.TriggerType, &d.ScopeType, &d.ComputeType,
		&d.RunnerTags, &d.TimeoutSeconds, &d.MaxRetries, &d.Priority,
		&defJSON, &d.Enabled, &d.CreatedAt, &d.UpdatedAt,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying job definition by ID: %w", err)
	}
	if defJSON != nil {
		if err := json.Unmarshal(defJSON, &d.Definition); err != nil {
			return nil, fmt.Errorf("unmarshaling definition: %w", err)
		}
	}
	return d, nil
}

// ---------------------------------------------------------------------------
// Jobs
// ---------------------------------------------------------------------------

// CreateJob inserts a new job.
func (r *JobRepository) CreateJob(ctx context.Context, j *Job) error {
	scopeJSON, err := json.Marshal(j.ScopeMetadata)
	if err != nil {
		return fmt.Errorf("marshaling scope metadata: %w", err)
	}

	err = r.db.pool.QueryRow(ctx, `
		INSERT INTO jobs (job_definition_id, definition_name, status, priority,
		                  item_id, project_id, scope_metadata,
		                  runner_tags, timeout_seconds, max_retries, created_by)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
		RETURNING id, created_at
	`, j.JobDefinitionID, j.DefinitionName, "pending", j.Priority,
		j.ItemID, j.ProjectID, scopeJSON,
		j.RunnerTags, j.TimeoutSeconds, j.MaxRetries, j.CreatedBy,
	).Scan(&j.ID, &j.CreatedAt)
	if err != nil {
		return fmt.Errorf("creating job: %w", err)
	}
	j.Status = "pending"
	return nil
}

// GetJob returns a job by ID.
func (r *JobRepository) GetJob(ctx context.Context, jobID string) (*Job, error) {
	j := &Job{}
	var scopeJSON, resultJSON []byte
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, job_definition_id, definition_name, status, priority,
		       item_id, project_id, scope_metadata, runner_id, runner_tags,
		       created_at, claimed_at, started_at, completed_at,
		       timeout_seconds, expires_at, progress, progress_message,
		       result, error_message, retry_count, max_retries,
		       created_by, cancelled_by
		FROM jobs WHERE id = $1
	`, jobID).Scan(
		&j.ID, &j.JobDefinitionID, &j.DefinitionName, &j.Status, &j.Priority,
		&j.ItemID, &j.ProjectID, &scopeJSON, &j.RunnerID, &j.RunnerTags,
		&j.CreatedAt, &j.ClaimedAt, &j.StartedAt, &j.CompletedAt,
		&j.TimeoutSeconds, &j.ExpiresAt, &j.Progress, &j.ProgressMessage,
		&resultJSON, &j.ErrorMessage, &j.RetryCount, &j.MaxRetries,
		&j.CreatedBy, &j.CancelledBy,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying job: %w", err)
	}
	if scopeJSON != nil {
		if err := json.Unmarshal(scopeJSON, &j.ScopeMetadata); err != nil {
			return nil, fmt.Errorf("unmarshaling scope metadata: %w", err)
		}
	}
	if resultJSON != nil {
		if err := json.Unmarshal(resultJSON, &j.Result); err != nil {
			return nil, fmt.Errorf("unmarshaling result: %w", err)
		}
	}
	return j, nil
}

// ListJobs returns jobs matching optional filters.
func (r *JobRepository) ListJobs(ctx context.Context, status, itemID string, limit, offset int) ([]*Job, error) {
	query := `
		SELECT id, job_definition_id, definition_name, status, priority,
		       item_id, project_id, scope_metadata, runner_id, runner_tags,
		       created_at, claimed_at, started_at, completed_at,
		       timeout_seconds, expires_at, progress, progress_message,
		       result, error_message, retry_count, max_retries,
		       created_by, cancelled_by
		FROM jobs WHERE 1=1`
	args := []any{}
	argN := 1

	if status != "" {
		query += fmt.Sprintf(" AND status = $%d", argN)
		args = append(args, status)
		argN++
	}
	if itemID != "" {
		query += fmt.Sprintf(" AND item_id = $%d", argN)
		args = append(args, itemID)
		argN++
	}

	query += " ORDER BY created_at DESC"

	if limit > 0 {
		query += fmt.Sprintf(" LIMIT $%d", argN)
		args = append(args, limit)
		argN++
	}
	if offset > 0 {
		query += fmt.Sprintf(" OFFSET $%d", argN)
		args = append(args, offset)
	}

	rows, err := r.db.pool.Query(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("querying jobs: %w", err)
	}
	defer rows.Close()
	return scanJobs(rows)
}

// ListSolverJobs returns solver jobs (definition_name LIKE 'assembly-%') with optional filters.
func (r *JobRepository) ListSolverJobs(ctx context.Context, status, itemID, operation string, limit, offset int) ([]*Job, error) {
	query := `
		SELECT id, job_definition_id, definition_name, status, priority,
		       item_id, project_id, scope_metadata, runner_id, runner_tags,
		       created_at, claimed_at, started_at, completed_at,
		       timeout_seconds, expires_at, progress, progress_message,
		       result, error_message, retry_count, max_retries,
		       created_by, cancelled_by
		FROM jobs WHERE definition_name LIKE 'assembly-%'`
	args := []any{}
	argN := 1

	if status != "" {
		query += fmt.Sprintf(" AND status = $%d", argN)
		args = append(args, status)
		argN++
	}
	if itemID != "" {
		query += fmt.Sprintf(" AND item_id = $%d", argN)
		args = append(args, itemID)
		argN++
	}
	if operation != "" {
		query += fmt.Sprintf(" AND scope_metadata->>'operation' = $%d", argN)
		args = append(args, operation)
		argN++
	}

	query += " ORDER BY created_at DESC"

	if limit > 0 {
		query += fmt.Sprintf(" LIMIT $%d", argN)
		args = append(args, limit)
		argN++
	}
	if offset > 0 {
		query += fmt.Sprintf(" OFFSET $%d", argN)
		args = append(args, offset)
	}

	rows, err := r.db.pool.Query(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("querying solver jobs: %w", err)
	}
	defer rows.Close()
	return scanJobs(rows)
}

// ClaimJob atomically claims the next available job matching the runner's tags.
// Uses SELECT FOR UPDATE SKIP LOCKED for exactly-once delivery.
func (r *JobRepository) ClaimJob(ctx context.Context, runnerID string, tags []string) (*Job, error) {
	j := &Job{}
	var scopeJSON, resultJSON []byte
	err := r.db.pool.QueryRow(ctx, `
		WITH claimable AS (
			SELECT id FROM jobs
			WHERE status = 'pending' AND runner_tags <@ $2::text[]
			ORDER BY priority ASC, created_at ASC
			LIMIT 1
			FOR UPDATE SKIP LOCKED
		)
		UPDATE jobs SET
			status = 'claimed',
			runner_id = $1,
			claimed_at = now(),
			expires_at = now() + (timeout_seconds || ' seconds')::interval
		FROM claimable
		WHERE jobs.id = claimable.id
		RETURNING jobs.id, jobs.job_definition_id, jobs.definition_name, jobs.status,
		          jobs.priority, jobs.item_id, jobs.project_id, jobs.scope_metadata,
		          jobs.runner_id, jobs.runner_tags, jobs.created_at, jobs.claimed_at,
		          jobs.started_at, jobs.completed_at, jobs.timeout_seconds, jobs.expires_at,
		          jobs.progress, jobs.progress_message, jobs.result, jobs.error_message,
		          jobs.retry_count, jobs.max_retries, jobs.created_by, jobs.cancelled_by
	`, runnerID, tags).Scan(
		&j.ID, &j.JobDefinitionID, &j.DefinitionName, &j.Status,
		&j.Priority, &j.ItemID, &j.ProjectID, &scopeJSON,
		&j.RunnerID, &j.RunnerTags, &j.CreatedAt, &j.ClaimedAt,
		&j.StartedAt, &j.CompletedAt, &j.TimeoutSeconds, &j.ExpiresAt,
		&j.Progress, &j.ProgressMessage, &resultJSON, &j.ErrorMessage,
		&j.RetryCount, &j.MaxRetries, &j.CreatedBy, &j.CancelledBy,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("claiming job: %w", err)
	}
	if scopeJSON != nil {
		if err := json.Unmarshal(scopeJSON, &j.ScopeMetadata); err != nil {
			return nil, fmt.Errorf("unmarshaling scope metadata: %w", err)
		}
	}
	if resultJSON != nil {
		if err := json.Unmarshal(resultJSON, &j.Result); err != nil {
			return nil, fmt.Errorf("unmarshaling result: %w", err)
		}
	}
	return j, nil
}

// StartJob transitions a claimed job to running.
func (r *JobRepository) StartJob(ctx context.Context, jobID, runnerID string) error {
	result, err := r.db.pool.Exec(ctx, `
		UPDATE jobs SET status = 'running', started_at = now()
		WHERE id = $1 AND runner_id = $2 AND status = 'claimed'
	`, jobID, runnerID)
	if err != nil {
		return fmt.Errorf("starting job: %w", err)
	}
	if result.RowsAffected() == 0 {
		return fmt.Errorf("job %s not claimable by runner %s or not in claimed state", jobID, runnerID)
	}
	return nil
}

// UpdateProgress updates a running job's progress.
func (r *JobRepository) UpdateProgress(ctx context.Context, jobID, runnerID string, progress int, message string) error {
	var msg *string
	if message != "" {
		msg = &message
	}
	result, err := r.db.pool.Exec(ctx, `
		UPDATE jobs SET progress = $3, progress_message = $4
		WHERE id = $1 AND runner_id = $2 AND status IN ('claimed', 'running')
	`, jobID, runnerID, progress, msg)
	if err != nil {
		return fmt.Errorf("updating progress: %w", err)
	}
	if result.RowsAffected() == 0 {
		return fmt.Errorf("job %s not owned by runner %s or not active", jobID, runnerID)
	}
	return nil
}

// CompleteJob marks a job as completed with optional result data.
func (r *JobRepository) CompleteJob(ctx context.Context, jobID, runnerID string, resultData map[string]any) error {
	var resultJSON []byte
	var err error
	if resultData != nil {
		resultJSON, err = json.Marshal(resultData)
		if err != nil {
			return fmt.Errorf("marshaling result: %w", err)
		}
	}

	res, err := r.db.pool.Exec(ctx, `
		UPDATE jobs SET
			status = 'completed',
			progress = 100,
			result = $3,
			completed_at = now()
		WHERE id = $1 AND runner_id = $2 AND status IN ('claimed', 'running')
	`, jobID, runnerID, resultJSON)
	if err != nil {
		return fmt.Errorf("completing job: %w", err)
	}
	if res.RowsAffected() == 0 {
		return fmt.Errorf("job %s not owned by runner %s or not active", jobID, runnerID)
	}
	return nil
}

// FailJob marks a job as failed with an error message.
func (r *JobRepository) FailJob(ctx context.Context, jobID, runnerID string, errMsg string) error {
	res, err := r.db.pool.Exec(ctx, `
		UPDATE jobs SET
			status = 'failed',
			error_message = $3,
			completed_at = now()
		WHERE id = $1 AND runner_id = $2 AND status IN ('claimed', 'running')
	`, jobID, runnerID, errMsg)
	if err != nil {
		return fmt.Errorf("failing job: %w", err)
	}
	if res.RowsAffected() == 0 {
		return fmt.Errorf("job %s not owned by runner %s or not active", jobID, runnerID)
	}
	return nil
}

// CancelJob cancels a pending or active job.
func (r *JobRepository) CancelJob(ctx context.Context, jobID string, cancelledBy string) error {
	res, err := r.db.pool.Exec(ctx, `
		UPDATE jobs SET
			status = 'cancelled',
			cancelled_by = $2,
			completed_at = now()
		WHERE id = $1 AND status IN ('pending', 'claimed', 'running')
	`, jobID, cancelledBy)
	if err != nil {
		return fmt.Errorf("cancelling job: %w", err)
	}
	if res.RowsAffected() == 0 {
		return fmt.Errorf("job %s not cancellable", jobID)
	}
	return nil
}

// TimeoutExpiredJobs marks expired claimed/running jobs as failed.
// Returns the number of jobs timed out.
func (r *JobRepository) TimeoutExpiredJobs(ctx context.Context) (int64, error) {
	result, err := r.db.pool.Exec(ctx, `
		UPDATE jobs SET
			status = 'failed',
			error_message = 'job timed out',
			completed_at = now()
		WHERE status IN ('claimed', 'running')
		  AND expires_at IS NOT NULL
		  AND expires_at < now()
	`)
	if err != nil {
		return 0, fmt.Errorf("timing out expired jobs: %w", err)
	}
	return result.RowsAffected(), nil
}

// ---------------------------------------------------------------------------
// Job Log
// ---------------------------------------------------------------------------

// AppendLog adds a log entry to a job.
func (r *JobRepository) AppendLog(ctx context.Context, entry *JobLogEntry) error {
	metaJSON, err := json.Marshal(entry.Metadata)
	if err != nil {
		return fmt.Errorf("marshaling log metadata: %w", err)
	}

	err = r.db.pool.QueryRow(ctx, `
		INSERT INTO job_log (job_id, level, message, metadata)
		VALUES ($1, $2, $3, $4)
		RETURNING id, timestamp
	`, entry.JobID, entry.Level, entry.Message, metaJSON,
	).Scan(&entry.ID, &entry.Timestamp)
	if err != nil {
		return fmt.Errorf("appending job log: %w", err)
	}
	return nil
}

// GetJobLogs returns all log entries for a job.
func (r *JobRepository) GetJobLogs(ctx context.Context, jobID string) ([]*JobLogEntry, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT id, job_id, timestamp, level, message, metadata
		FROM job_log WHERE job_id = $1 ORDER BY timestamp ASC
	`, jobID)
	if err != nil {
		return nil, fmt.Errorf("querying job logs: %w", err)
	}
	defer rows.Close()

	var entries []*JobLogEntry
	for rows.Next() {
		e := &JobLogEntry{}
		var metaJSON []byte
		if err := rows.Scan(&e.ID, &e.JobID, &e.Timestamp, &e.Level, &e.Message, &metaJSON); err != nil {
			return nil, fmt.Errorf("scanning job log: %w", err)
		}
		if metaJSON != nil {
			if err := json.Unmarshal(metaJSON, &e.Metadata); err != nil {
				return nil, fmt.Errorf("unmarshaling log metadata: %w", err)
			}
		}
		entries = append(entries, e)
	}
	return entries, rows.Err()
}

// ---------------------------------------------------------------------------
// Runners
// ---------------------------------------------------------------------------

// RegisterRunner creates a new runner record.
func (r *JobRepository) RegisterRunner(ctx context.Context, runner *Runner) error {
	metaJSON, err := json.Marshal(runner.Metadata)
	if err != nil {
		return fmt.Errorf("marshaling runner metadata: %w", err)
	}

	err = r.db.pool.QueryRow(ctx, `
		INSERT INTO runners (name, token_hash, token_prefix, tags, status, metadata)
		VALUES ($1, $2, $3, $4, 'offline', $5)
		RETURNING id, created_at, updated_at
	`, runner.Name, runner.TokenHash, runner.TokenPrefix, runner.Tags, metaJSON,
	).Scan(&runner.ID, &runner.CreatedAt, &runner.UpdatedAt)
	if err != nil {
		return fmt.Errorf("registering runner: %w", err)
	}
	runner.Status = "offline"
	return nil
}

// GetRunnerByToken looks up a runner by token hash.
func (r *JobRepository) GetRunnerByToken(ctx context.Context, tokenHash string) (*Runner, error) {
	runner := &Runner{}
	var metaJSON []byte
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, name, token_hash, token_prefix, tags, status,
		       last_heartbeat, last_job_id, metadata, created_at, updated_at
		FROM runners WHERE token_hash = $1
	`, tokenHash).Scan(
		&runner.ID, &runner.Name, &runner.TokenHash, &runner.TokenPrefix,
		&runner.Tags, &runner.Status, &runner.LastHeartbeat, &runner.LastJobID,
		&metaJSON, &runner.CreatedAt, &runner.UpdatedAt,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying runner by token: %w", err)
	}
	if metaJSON != nil {
		if err := json.Unmarshal(metaJSON, &runner.Metadata); err != nil {
			return nil, fmt.Errorf("unmarshaling runner metadata: %w", err)
		}
	}
	return runner, nil
}

// GetRunner returns a runner by ID.
func (r *JobRepository) GetRunner(ctx context.Context, runnerID string) (*Runner, error) {
	runner := &Runner{}
	var metaJSON []byte
	err := r.db.pool.QueryRow(ctx, `
		SELECT id, name, token_hash, token_prefix, tags, status,
		       last_heartbeat, last_job_id, metadata, created_at, updated_at
		FROM runners WHERE id = $1
	`, runnerID).Scan(
		&runner.ID, &runner.Name, &runner.TokenHash, &runner.TokenPrefix,
		&runner.Tags, &runner.Status, &runner.LastHeartbeat, &runner.LastJobID,
		&metaJSON, &runner.CreatedAt, &runner.UpdatedAt,
	)
	if err == pgx.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("querying runner: %w", err)
	}
	if metaJSON != nil {
		if err := json.Unmarshal(metaJSON, &runner.Metadata); err != nil {
			return nil, fmt.Errorf("unmarshaling runner metadata: %w", err)
		}
	}
	return runner, nil
}

// Heartbeat updates a runner's heartbeat timestamp and sets status to online.
func (r *JobRepository) Heartbeat(ctx context.Context, runnerID string) error {
	res, err := r.db.pool.Exec(ctx, `
		UPDATE runners SET
			status = 'online',
			last_heartbeat = now(),
			updated_at = now()
		WHERE id = $1
	`, runnerID)
	if err != nil {
		return fmt.Errorf("updating heartbeat: %w", err)
	}
	if res.RowsAffected() == 0 {
		return fmt.Errorf("runner %s not found", runnerID)
	}
	return nil
}

// ListRunners returns all registered runners.
func (r *JobRepository) ListRunners(ctx context.Context) ([]*Runner, error) {
	rows, err := r.db.pool.Query(ctx, `
		SELECT id, name, token_hash, token_prefix, tags, status,
		       last_heartbeat, last_job_id, metadata, created_at, updated_at
		FROM runners ORDER BY name
	`)
	if err != nil {
		return nil, fmt.Errorf("querying runners: %w", err)
	}
	defer rows.Close()

	var runners []*Runner
	for rows.Next() {
		runner := &Runner{}
		var metaJSON []byte
		if err := rows.Scan(
			&runner.ID, &runner.Name, &runner.TokenHash, &runner.TokenPrefix,
			&runner.Tags, &runner.Status, &runner.LastHeartbeat, &runner.LastJobID,
			&metaJSON, &runner.CreatedAt, &runner.UpdatedAt,
		); err != nil {
			return nil, fmt.Errorf("scanning runner: %w", err)
		}
		if metaJSON != nil {
			if err := json.Unmarshal(metaJSON, &runner.Metadata); err != nil {
				return nil, fmt.Errorf("unmarshaling runner metadata: %w", err)
			}
		}
		runners = append(runners, runner)
	}
	return runners, rows.Err()
}

// DeleteRunner removes a runner by ID.
func (r *JobRepository) DeleteRunner(ctx context.Context, runnerID string) error {
	res, err := r.db.pool.Exec(ctx, `DELETE FROM runners WHERE id = $1`, runnerID)
	if err != nil {
		return fmt.Errorf("deleting runner: %w", err)
	}
	if res.RowsAffected() == 0 {
		return fmt.Errorf("runner %s not found", runnerID)
	}
	return nil
}

// ExpireStaleRunners marks runners with no recent heartbeat as offline.
func (r *JobRepository) ExpireStaleRunners(ctx context.Context, timeout time.Duration) (int64, error) {
	result, err := r.db.pool.Exec(ctx, `
		UPDATE runners SET status = 'offline', updated_at = now()
		WHERE status = 'online'
		  AND last_heartbeat < now() - $1::interval
	`, timeout.String())
	if err != nil {
		return 0, fmt.Errorf("expiring stale runners: %w", err)
	}
	return result.RowsAffected(), nil
}

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

func scanJobDefinitions(rows pgx.Rows) ([]*JobDefinitionRecord, error) {
	var defs []*JobDefinitionRecord
	for rows.Next() {
		d := &JobDefinitionRecord{}
		var defJSON []byte
		if err := rows.Scan(
			&d.ID, &d.Name, &d.Version, &d.TriggerType, &d.ScopeType, &d.ComputeType,
			&d.RunnerTags, &d.TimeoutSeconds, &d.MaxRetries, &d.Priority,
			&defJSON, &d.Enabled, &d.CreatedAt, &d.UpdatedAt,
		); err != nil {
			return nil, fmt.Errorf("scanning job definition: %w", err)
		}
		if defJSON != nil {
			if err := json.Unmarshal(defJSON, &d.Definition); err != nil {
				return nil, fmt.Errorf("unmarshaling definition: %w", err)
			}
		}
		defs = append(defs, d)
	}
	return defs, rows.Err()
}

func scanJobs(rows pgx.Rows) ([]*Job, error) {
	var jobs []*Job
	for rows.Next() {
		j := &Job{}
		var scopeJSON, resultJSON []byte
		if err := rows.Scan(
			&j.ID, &j.JobDefinitionID, &j.DefinitionName, &j.Status, &j.Priority,
			&j.ItemID, &j.ProjectID, &scopeJSON, &j.RunnerID, &j.RunnerTags,
			&j.CreatedAt, &j.ClaimedAt, &j.StartedAt, &j.CompletedAt,
			&j.TimeoutSeconds, &j.ExpiresAt, &j.Progress, &j.ProgressMessage,
			&resultJSON, &j.ErrorMessage, &j.RetryCount, &j.MaxRetries,
			&j.CreatedBy, &j.CancelledBy,
		); err != nil {
			return nil, fmt.Errorf("scanning job: %w", err)
		}
		if scopeJSON != nil {
			if err := json.Unmarshal(scopeJSON, &j.ScopeMetadata); err != nil {
				return nil, fmt.Errorf("unmarshaling scope metadata: %w", err)
			}
		}
		if resultJSON != nil {
			if err := json.Unmarshal(resultJSON, &j.Result); err != nil {
				return nil, fmt.Errorf("unmarshaling result: %w", err)
			}
		}
		jobs = append(jobs, j)
	}
	return jobs, rows.Err()
}