package particle

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

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
	"go.jetify.com/typeid"
)

var errNotFound = errors.New("not found")
var errAccessDenied = errors.New("access denied")

type particleIDPrefix struct{}

func (particleIDPrefix) Prefix() string { return "particle" }

type particleID struct {
	typeid.TypeID[particleIDPrefix]
}

func newParticleID() (particleID, error) {
	return typeid.New[particleID]()
}

type repository interface {
	create(ctx context.Context, p *Particle) (*Particle, error)
	getByID(ctx context.Context, id string) (*Particle, error)
	update(ctx context.Context, id string, data json.RawMessage, updatedAt time.Time) error
	delete(ctx context.Context, id string) error

	list(ctx context.Context, networkID string, parentID *string, requesterEmail string, filter ListFilter, limit int, cursor *Cursor) ([]*Particle, error)

	setVisibility(ctx context.Context, id string, mode VisibilityMode) error
	addMembers(ctx context.Context, particleID string, emails []string) error
	removeMembers(ctx context.Context, particleID string, emails []string) error
	getMembers(ctx context.Context, particleID string) ([]string, error)
	getMembersMap(ctx context.Context, particleIDs []string) (map[string][]string, error)

	// getAncestorChain returns the particle and all its ancestors (for access checks)
	getAncestorChain(ctx context.Context, particleID string) ([]*Particle, error)
	isMemberOf(ctx context.Context, particleID, email string) (bool, error)

	// Seen tracking
	markSeen(ctx context.Context, particleID, email string) error
	getSeenMap(ctx context.Context, particleIDs []string, email string) (map[string]bool, error)
	getUnseenCounts(ctx context.Context, streamIDs []string, email string) (map[string]int, error)

	// Ack tracking
	ack(ctx context.Context, particleID, email string) error
	getAcksMap(ctx context.Context, particleIDs []string) (map[string][]AckInfo, error)
}

type repositoryImpl struct {
	pool *pgxpool.Pool
}

func newRepository(pool *pgxpool.Pool) repository {
	return &repositoryImpl{pool: pool}
}

func (r *repositoryImpl) create(ctx context.Context, p *Particle) (*Particle, error) {
	id, err := newParticleID()
	if err != nil {
		return nil, err
	}

	var result Particle
	err = r.pool.QueryRow(ctx,
		`INSERT INTO particles (id, type, network_id, parent_id, created_by_email, visibility, data)
		 VALUES ($1, $2, $3, $4, $5, $6, $7)
		 RETURNING id, type, network_id, parent_id, created_by_email, visibility, data, updated_at, created_at`,
		id.String(), p.Type, p.NetworkID, p.ParentID, p.CreatedByEmail, p.Visibility, p.Data,
	).Scan(&result.ID, &result.Type, &result.NetworkID, &result.ParentID, &result.CreatedByEmail,
		&result.Visibility, &result.Data, &result.UpdatedAt, &result.CreatedAt)
	if err != nil {
		return nil, err
	}

	return &result, nil
}

func (r *repositoryImpl) getByID(ctx context.Context, id string) (*Particle, error) {
	var p Particle
	err := r.pool.QueryRow(ctx,
		`SELECT id, type, network_id, parent_id, created_by_email, visibility, data, updated_at, created_at
		 FROM particles WHERE id = $1`,
		id,
	).Scan(&p.ID, &p.Type, &p.NetworkID, &p.ParentID, &p.CreatedByEmail,
		&p.Visibility, &p.Data, &p.UpdatedAt, &p.CreatedAt)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, errNotFound
		}
		return nil, err
	}
	return &p, nil
}

func (r *repositoryImpl) update(ctx context.Context, id string, data json.RawMessage, updatedAt time.Time) error {
	result, err := r.pool.Exec(ctx,
		`UPDATE particles SET data = $1, updated_at = $2 WHERE id = $3`,
		data, updatedAt, id,
	)
	if err != nil {
		return err
	}
	if result.RowsAffected() == 0 {
		return errNotFound
	}
	return nil
}

func (r *repositoryImpl) delete(ctx context.Context, id string) error {
	result, err := r.pool.Exec(ctx, `DELETE FROM particles WHERE id = $1`, id)
	if err != nil {
		return err
	}
	if result.RowsAffected() == 0 {
		return errNotFound
	}
	return nil
}

func (r *repositoryImpl) list(ctx context.Context, networkID string, parentID *string, requesterEmail string, filter ListFilter, limit int, cursor *Cursor) ([]*Particle, error) {
	query := `SELECT id, type, network_id, parent_id, created_by_email, visibility, data, updated_at, created_at
		 FROM particles p WHERE p.network_id = $1`

	args := []any{networkID}
	argIdx := 2

	if parentID != nil {
		query += ` AND p.parent_id = $` + string(rune('0'+argIdx))
		args = append(args, *parentID)
		argIdx++
	} else {
		query += ` AND p.parent_id IS NULL`
	}

	// Filter by visibility: include if network_all, inherited, OR user is a member
	query += ` AND (p.visibility = 'network_all' OR p.visibility = 'inherited' OR EXISTS (SELECT 1 FROM particle_members pm WHERE pm.particle_id = p.id AND pm.email = $` + string(rune('0'+argIdx)) + `))`
	args = append(args, requesterEmail)
	argIdx++

	if len(filter.Types) > 0 {
		query += ` AND p.type = ANY($` + string(rune('0'+argIdx)) + `)`
		typeStrings := make([]string, len(filter.Types))
		for i, t := range filter.Types {
			typeStrings[i] = string(t)
		}
		args = append(args, typeStrings)
		argIdx++
	}

	if cursor != nil {
		if cursor.Direction == "before" {
			query += ` AND p.updated_at > $` + string(rune('0'+argIdx))
		} else {
			query += ` AND p.updated_at < $` + string(rune('0'+argIdx))
		}
		args = append(args, cursor.Position)
		argIdx++
	}

	query += ` ORDER BY p.updated_at DESC LIMIT $` + string(rune('0'+argIdx))
	args = append(args, limit)

	rows, err := r.pool.Query(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	return scanParticles(rows)
}

func scanParticles(rows pgx.Rows) ([]*Particle, error) {
	var particles []*Particle
	for rows.Next() {
		var p Particle
		if err := rows.Scan(&p.ID, &p.Type, &p.NetworkID, &p.ParentID, &p.CreatedByEmail,
			&p.Visibility, &p.Data, &p.UpdatedAt, &p.CreatedAt); err != nil {
			return nil, err
		}
		particles = append(particles, &p)
	}
	return particles, rows.Err()
}

func (r *repositoryImpl) setVisibility(ctx context.Context, id string, mode VisibilityMode) error {
	result, err := r.pool.Exec(ctx,
		`UPDATE particles SET visibility = $1, updated_at = NOW() WHERE id = $2`,
		mode, id,
	)
	if err != nil {
		return err
	}
	if result.RowsAffected() == 0 {
		return errNotFound
	}
	return nil
}

func (r *repositoryImpl) addMembers(ctx context.Context, particleID string, emails []string) error {
	for _, email := range emails {
		_, err := r.pool.Exec(ctx,
			`INSERT INTO particle_members (particle_id, email) VALUES ($1, $2)
			 ON CONFLICT (particle_id, email) DO NOTHING`,
			particleID, email,
		)
		if err != nil {
			return err
		}
	}
	return nil
}

func (r *repositoryImpl) removeMembers(ctx context.Context, particleID string, emails []string) error {
	for _, email := range emails {
		_, err := r.pool.Exec(ctx,
			`DELETE FROM particle_members WHERE particle_id = $1 AND email = $2`,
			particleID, email,
		)
		if err != nil {
			return err
		}
	}
	return nil
}

func (r *repositoryImpl) getMembers(ctx context.Context, particleID string) ([]string, error) {
	rows, err := r.pool.Query(ctx,
		`SELECT email FROM particle_members WHERE particle_id = $1`,
		particleID,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var emails []string
	for rows.Next() {
		var email string
		if err := rows.Scan(&email); err != nil {
			return nil, err
		}
		emails = append(emails, email)
	}
	return emails, rows.Err()
}

func (r *repositoryImpl) getMembersMap(ctx context.Context, particleIDs []string) (map[string][]string, error) {
	if len(particleIDs) == 0 {
		return map[string][]string{}, nil
	}

	rows, err := r.pool.Query(ctx,
		`SELECT particle_id, email FROM particle_members WHERE particle_id = ANY($1)`,
		particleIDs,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	result := make(map[string][]string)
	for rows.Next() {
		var particleID, email string
		if err := rows.Scan(&particleID, &email); err != nil {
			return nil, err
		}
		result[particleID] = append(result[particleID], email)
	}
	return result, rows.Err()
}

func (r *repositoryImpl) getAncestorChain(ctx context.Context, particleID string) ([]*Particle, error) {
	rows, err := r.pool.Query(ctx, `
		WITH RECURSIVE ancestors AS (
			SELECT id, type, network_id, parent_id, created_by_email, visibility, data, updated_at, created_at
			FROM particles WHERE id = $1
			UNION ALL
			SELECT p.id, p.type, p.network_id, p.parent_id, p.created_by_email, p.visibility, p.data, p.updated_at, p.created_at
			FROM particles p JOIN ancestors a ON p.id = a.parent_id
		)
		SELECT id, type, network_id, parent_id, created_by_email, visibility, data, updated_at, created_at
		FROM ancestors;
	`, particleID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	particles, err := scanParticles(rows)
	if err != nil {
		return nil, err
	}
	if len(particles) == 0 {
		return nil, errNotFound
	}
	return particles, nil
}

func (r *repositoryImpl) isMemberOf(ctx context.Context, particleID, email string) (bool, error) {
	var isMember bool
	err := r.pool.QueryRow(ctx, `
		SELECT EXISTS(SELECT 1 FROM particle_members WHERE particle_id = $1 AND email = $2)
	`, particleID, email).Scan(&isMember)
	return isMember, err
}

func (r *repositoryImpl) markSeen(ctx context.Context, particleID, email string) error {
	_, err := r.pool.Exec(ctx,
		`INSERT INTO particle_seen (particle_id, email) VALUES ($1, $2)
		 ON CONFLICT (particle_id, email) DO NOTHING`,
		particleID, email,
	)
	return err
}

func (r *repositoryImpl) getSeenMap(ctx context.Context, particleIDs []string, email string) (map[string]bool, error) {
	if len(particleIDs) == 0 {
		return map[string]bool{}, nil
	}

	rows, err := r.pool.Query(ctx,
		`SELECT particle_id FROM particle_seen WHERE particle_id = ANY($1) AND email = $2`,
		particleIDs, email,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	result := make(map[string]bool)
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		result[id] = true
	}
	return result, rows.Err()
}

func (r *repositoryImpl) getUnseenCounts(ctx context.Context, streamIDs []string, email string) (map[string]int, error) {
	if len(streamIDs) == 0 {
		return map[string]int{}, nil
	}

	rows, err := r.pool.Query(ctx, `
		SELECT p.parent_id, COUNT(*)
		FROM particles p
		WHERE p.parent_id = ANY($1)
		  AND NOT EXISTS (SELECT 1 FROM particle_seen ps WHERE ps.particle_id = p.id AND ps.email = $2)
		  AND (p.visibility = 'network_all' OR p.visibility = 'inherited'
		       OR EXISTS (SELECT 1 FROM particle_members pm WHERE pm.particle_id = p.id AND pm.email = $2))
		GROUP BY p.parent_id
	`, streamIDs, email)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	result := make(map[string]int)
	for rows.Next() {
		var parentID string
		var count int
		if err := rows.Scan(&parentID, &count); err != nil {
			return nil, err
		}
		result[parentID] = count
	}
	return result, rows.Err()
}

func (r *repositoryImpl) ack(ctx context.Context, particleID, email string) error {
	_, err := r.pool.Exec(ctx,
		`INSERT INTO particle_acks (particle_id, email) VALUES ($1, $2)
		 ON CONFLICT (particle_id, email) DO NOTHING`,
		particleID, email,
	)
	return err
}

func (r *repositoryImpl) getAcksMap(ctx context.Context, particleIDs []string) (map[string][]AckInfo, error) {
	if len(particleIDs) == 0 {
		return map[string][]AckInfo{}, nil
	}

	rows, err := r.pool.Query(ctx,
		`SELECT particle_id, email, acked_at FROM particle_acks WHERE particle_id = ANY($1) ORDER BY acked_at`,
		particleIDs,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	result := make(map[string][]AckInfo)
	for rows.Next() {
		var particleID string
		var info AckInfo
		if err := rows.Scan(&particleID, &info.Email, &info.AckedAt); err != nil {
			return nil, err
		}
		result[particleID] = append(result[particleID], info)
	}
	return result, rows.Err()
}