package storage

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

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"
	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/alchemistkay/guestguard/internal/domain"
)

type EventRepo struct {
	pool *pgxpool.Pool
}

func NewEventRepo(db *DB) *EventRepo {
	return &EventRepo{pool: db.Pool}
}

type CreateEventParams struct {
	HostID      uuid.UUID
	Name        string
	Slug        string
	EventDate   time.Time
	Venue       string
	MaxCapacity int
	Settings    map[string]any
	Status      domain.EventStatus
}

func (r *EventRepo) Create(ctx context.Context, p CreateEventParams) (*domain.Event, error) {
	settings := p.Settings
	if settings == nil {
		settings = map[string]any{}
	}
	settingsJSON, err := json.Marshal(settings)
	if err != nil {
		return nil, fmt.Errorf("marshal settings: %w", err)
	}

	// Block C: every new event needs a row in event_collaborators pointing
	// the host at the owner role. We do both inserts in one transaction so
	// an event can never exist without its owner row (the migration backfill
	// handles legacy events but not new ones).
	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	const q = `
        INSERT INTO events (host_id, name, slug, event_date, venue, max_capacity, settings, status)
        VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
        RETURNING id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
    `
	row := tx.QueryRow(ctx, q,
		p.HostID, p.Name, p.Slug, p.EventDate, p.Venue, p.MaxCapacity, settingsJSON, p.Status,
	)
	ev, err := scanEvent(row)
	if err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return nil, domain.ErrSlugTaken
		}
		return nil, err
	}

	if _, err := tx.Exec(ctx, `
        INSERT INTO event_collaborators (event_id, user_id, role, invited_at, accepted_at)
        VALUES ($1, $2, 'owner', now(), now())
    `, ev.ID, p.HostID); err != nil {
		return nil, fmt.Errorf("seed owner collaborator: %w", err)
	}

	// Block F: auto-seed reminder messages so the host gets the
	// "we'll nudge people for you" experience without lifting a finger.
	// Rows whose send_at would fall in the past are skipped by
	// SeedAutoReminders — typical for events created close to the date.
	// Hosts can edit / cancel any of these from the Communications tab.
	for _, m := range domain.SeedAutoReminders(ev.ID, ev.EventDate) {
		if _, err := tx.Exec(ctx, `
            INSERT INTO scheduled_messages
                (event_id, send_at, audience, channel, template_key, subject, body, status)
            VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
        `, m.EventID, m.SendAt, m.Audience, m.Channel,
			m.TemplateKey, m.Subject, m.Body, m.Status); err != nil {
			return nil, fmt.Errorf("seed auto-reminder %s: %w",
				ifNilString(m.TemplateKey), err)
		}
	}

	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}
	return ev, nil
}

// ifNilString is a tiny helper so the error message above stays readable
// when an auto-reminder row somehow doesn't carry a template key.
func ifNilString(p *string) string {
	if p == nil {
		return "<unknown>"
	}
	return *p
}

func (r *EventRepo) Get(ctx context.Context, id uuid.UUID) (*domain.Event, error) {
	const q = `
        SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
        FROM events WHERE id = $1
    `
	ev, err := scanEvent(r.pool.QueryRow(ctx, q, id))
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrEventNotFound
		}
		return nil, err
	}
	return ev, nil
}

// GetForHost is the authz-aware variant of Get. It returns ErrEventNotFound
// when the event either doesn't exist or doesn't belong to the host — by
// merging both cases we avoid leaking existence on cross-tenant lookups.
func (r *EventRepo) GetForHost(ctx context.Context, id, hostID uuid.UUID) (*domain.Event, error) {
	const q = `
        SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
        FROM events WHERE id = $1 AND host_id = $2
    `
	ev, err := scanEvent(r.pool.QueryRow(ctx, q, id, hostID))
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrEventNotFound
		}
		return nil, err
	}
	return ev, nil
}

// ListForUser returns every event the user has any accepted role on. The
// query unions events where the user is the legacy host_id with events
// they collaborate on (via Block C). Duplicates are deduped on event id.
// Block C — preferred over List for the dashboard since collaborators
// should see shared events too.
func (r *EventRepo) ListForUser(ctx context.Context, userID uuid.UUID, collabEventIDs []uuid.UUID, limit, offset int) ([]*domain.Event, error) {
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	if offset < 0 {
		offset = 0
	}
	rows, err := r.pool.Query(ctx, `
        SELECT DISTINCT
               id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
        FROM events
        WHERE host_id = $1
           OR id = ANY($2::uuid[])
        ORDER BY created_at DESC
        LIMIT $3 OFFSET $4
    `, userID, collabEventIDs, limit, offset)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []*domain.Event
	for rows.Next() {
		ev, err := scanEvent(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, ev)
	}
	return out, rows.Err()
}

func (r *EventRepo) List(ctx context.Context, hostID uuid.UUID, limit, offset int) ([]*domain.Event, error) {
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	if offset < 0 {
		offset = 0
	}

	var (
		rows pgx.Rows
		err  error
	)
	if hostID == uuid.Nil {
		rows, err = r.pool.Query(ctx, `
            SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
            FROM events
            ORDER BY created_at DESC
            LIMIT $1 OFFSET $2
        `, limit, offset)
	} else {
		rows, err = r.pool.Query(ctx, `
            SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
            FROM events
            WHERE host_id = $1
            ORDER BY created_at DESC
            LIMIT $2 OFFSET $3
        `, hostID, limit, offset)
	}
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []*domain.Event
	for rows.Next() {
		ev, err := scanEvent(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, ev)
	}
	return out, rows.Err()
}

type UpdateEventParams struct {
	Name        *string
	Slug        *string
	EventDate   *time.Time
	Venue       *string
	MaxCapacity *int
	Settings    *map[string]any
	Status      *domain.EventStatus
}

// UpdateByID applies the patch without an authz scope. Block C handlers
// run requireRole first, so re-checking host_id here would block legitimate
// editor-collaborators on someone else's event.
func (r *EventRepo) UpdateByID(ctx context.Context, id uuid.UUID, p UpdateEventParams) (*domain.Event, error) {
	return r.update(ctx, id, uuid.Nil, p, false)
}

// Update is the legacy host-scoped variant — preserved so a few owner-only
// call sites stay terse. New code should prefer UpdateByID + requireRole.
func (r *EventRepo) Update(ctx context.Context, id, hostID uuid.UUID, p UpdateEventParams) (*domain.Event, error) {
	return r.update(ctx, id, hostID, p, true)
}

func (r *EventRepo) update(ctx context.Context, id, hostID uuid.UUID, p UpdateEventParams, scopeToHost bool) (*domain.Event, error) {
	q := `
        UPDATE events SET
            name         = COALESCE($3, name),
            slug         = COALESCE($4, slug),
            event_date   = COALESCE($5, event_date),
            venue        = COALESCE($6, venue),
            max_capacity = COALESCE($7, max_capacity),
            settings     = COALESCE($8, settings),
            status       = COALESCE($9, status),
            updated_at   = now()
        WHERE id = $1`
	if scopeToHost {
		q += ` AND host_id = $2`
	} else {
		// Bind $2 anyway so the parameter count matches the call below.
		q += ` AND ($2::uuid IS NULL OR $2::uuid = host_id OR TRUE)`
	}
	q += `
        RETURNING id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at, fraud_medium_threshold, fraud_high_threshold, fraud_block_threshold
    `

	var settingsJSON []byte
	if p.Settings != nil {
		b, err := json.Marshal(*p.Settings)
		if err != nil {
			return nil, fmt.Errorf("marshal settings: %w", err)
		}
		settingsJSON = b
	}

	row := r.pool.QueryRow(ctx, q, id, hostID,
		p.Name, p.Slug, p.EventDate, p.Venue, p.MaxCapacity, settingsJSON, p.Status,
	)
	ev, err := scanEvent(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrEventNotFound
		}
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return nil, domain.ErrSlugTaken
		}
		return nil, err
	}
	return ev, nil
}

func (r *EventRepo) Delete(ctx context.Context, id, hostID uuid.UUID) error {
	tag, err := r.pool.Exec(ctx, `DELETE FROM events WHERE id = $1 AND host_id = $2`, id, hostID)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return domain.ErrEventNotFound
	}
	return nil
}

// DeleteByID is the post-Block-C path: requireRole(Owner) is enforced by
// the handler, so this query doesn't double-check host_id.
func (r *EventRepo) DeleteByID(ctx context.Context, id uuid.UUID) error {
	tag, err := r.pool.Exec(ctx, `DELETE FROM events WHERE id = $1`, id)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return domain.ErrEventNotFound
	}
	return nil
}

type rowScanner interface {
	Scan(dest ...any) error
}

func scanEvent(s rowScanner) (*domain.Event, error) {
	var (
		ev           domain.Event
		settingsJSON []byte
	)
	err := s.Scan(
		&ev.ID, &ev.HostID, &ev.Name, &ev.Slug, &ev.EventDate, &ev.Venue,
		&ev.MaxCapacity, &settingsJSON, &ev.Status, &ev.CreatedAt, &ev.UpdatedAt,
		&ev.FraudMediumThreshold, &ev.FraudHighThreshold, &ev.FraudBlockThreshold,
	)
	if err != nil {
		return nil, err
	}
	if len(settingsJSON) > 0 {
		if err := json.Unmarshal(settingsJSON, &ev.Settings); err != nil {
			return nil, fmt.Errorf("unmarshal settings: %w", err)
		}
	} else {
		ev.Settings = map[string]any{}
	}
	return &ev, nil
}