package ent

import (
	"context"
	"errors"
	"strings"
	"time"

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

	domain "knowfoolery/backend/services/game-session-service/internal/domain/session"
)

// SessionRepository implements game session persistence in PostgreSQL.
type SessionRepository struct {
	client *Client
}

// NewSessionRepository creates a new session repository.
func NewSessionRepository(client *Client) *SessionRepository {
	return &SessionRepository{client: client}
}

// EnsureSchema creates required tables and indexes.
func (r *SessionRepository) EnsureSchema(ctx context.Context) error {
	const ddl = `
CREATE TABLE IF NOT EXISTS game_sessions (
  id UUID PRIMARY KEY,
  player_id VARCHAR(128) NOT NULL,
  player_name VARCHAR(50) NOT NULL,
  status VARCHAR(16) NOT NULL,
  total_score INT NOT NULL DEFAULT 0,
  questions_asked INT NOT NULL DEFAULT 0,
  questions_correct INT NOT NULL DEFAULT 0,
  hints_used INT NOT NULL DEFAULT 0,
  current_question_id VARCHAR(64),
  current_attempts INT NOT NULL DEFAULT 0,
  current_hint_used BOOLEAN NOT NULL DEFAULT FALSE,
  question_started_at TIMESTAMPTZ,
  start_time TIMESTAMPTZ NOT NULL,
  end_time TIMESTAMPTZ,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
CREATE INDEX IF NOT EXISTS idx_game_sessions_player_status ON game_sessions (player_id, status);
CREATE INDEX IF NOT EXISTS idx_game_sessions_status_start ON game_sessions (status, start_time DESC);
CREATE INDEX IF NOT EXISTS idx_game_sessions_created_at ON game_sessions (created_at DESC);

CREATE TABLE IF NOT EXISTS session_attempts (
  id UUID PRIMARY KEY,
  session_id UUID NOT NULL,
  question_id VARCHAR(64) NOT NULL,
  attempt_number INT NOT NULL,
  provided_answer VARCHAR(500) NOT NULL,
  is_correct BOOLEAN NOT NULL,
  used_hint BOOLEAN NOT NULL,
  awarded_score INT NOT NULL,
  latency_ms INT NOT NULL,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
CREATE INDEX IF NOT EXISTS idx_session_attempts_session_question
  ON session_attempts (session_id, question_id, attempt_number);
CREATE INDEX IF NOT EXISTS idx_session_attempts_session_created ON session_attempts (session_id, created_at DESC);

CREATE TABLE IF NOT EXISTS session_events (
  id UUID PRIMARY KEY,
  session_id UUID NOT NULL,
  event_type VARCHAR(64) NOT NULL,
  metadata_json JSONB NOT NULL DEFAULT '{}'::jsonb,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
CREATE INDEX IF NOT EXISTS idx_session_events_session ON session_events (session_id, created_at DESC);
`
	_, err := r.client.Pool.Exec(ctx, ddl)
	return err
}

// CreateSession inserts a new game session.
func (r *SessionRepository) CreateSession(
	ctx context.Context,
	session *domain.GameSession,
) (*domain.GameSession, error) {
	id := uuid.NewString()
	now := time.Now().UTC()
	const q = `
INSERT INTO game_sessions (
 id, player_id, player_name, status, total_score, questions_asked, questions_correct, hints_used,
 current_question_id, current_attempts, current_hint_used, question_started_at,
 start_time, end_time, created_at, updated_at
)
VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16)
RETURNING id, player_id, player_name, status, total_score, questions_asked, questions_correct, hints_used,
 current_question_id, current_attempts, current_hint_used, question_started_at,
 start_time, end_time, created_at, updated_at`

	row := r.client.Pool.QueryRow(ctx, q,
		id,
		session.PlayerID,
		session.PlayerName,
		string(session.Status),
		session.TotalScore,
		session.QuestionsAsked,
		session.QuestionsCorrect,
		session.HintsUsed,
		nullIfEmpty(session.CurrentQuestionID),
		session.CurrentAttempts,
		session.CurrentHintUsed,
		session.QuestionStartedAt,
		session.StartTime,
		session.EndTime,
		now,
		now,
	)
	return scanSession(row)
}

// GetSessionByID returns a session by ID.
func (r *SessionRepository) GetSessionByID(ctx context.Context, id string) (*domain.GameSession, error) {
	const q = `
SELECT id, player_id, player_name, status, total_score, questions_asked, questions_correct, hints_used,
 current_question_id, current_attempts, current_hint_used, question_started_at,
 start_time, end_time, created_at, updated_at
FROM game_sessions WHERE id=$1`
	row := r.client.Pool.QueryRow(ctx, q, id)
	session, err := scanSession(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrSessionNotFound
		}
		return nil, err
	}
	return session, nil
}

// GetActiveSessionByPlayerID returns an active session for player.
func (r *SessionRepository) GetActiveSessionByPlayerID(
	ctx context.Context,
	playerID string,
) (*domain.GameSession, error) {
	const q = `
SELECT id, player_id, player_name, status, total_score, questions_asked, questions_correct, hints_used,
 current_question_id, current_attempts, current_hint_used, question_started_at,
 start_time, end_time, created_at, updated_at
FROM game_sessions WHERE player_id=$1 AND status='active' ORDER BY start_time DESC LIMIT 1`
	row := r.client.Pool.QueryRow(ctx, q, playerID)
	session, err := scanSession(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrSessionNotFound
		}
		return nil, err
	}
	return session, nil
}

// UpdateSession updates mutable session fields.
func (r *SessionRepository) UpdateSession(
	ctx context.Context,
	session *domain.GameSession,
) (*domain.GameSession, error) {
	const q = `
UPDATE game_sessions
SET status=$2, total_score=$3, questions_asked=$4, questions_correct=$5, hints_used=$6,
 current_question_id=$7, current_attempts=$8, current_hint_used=$9, question_started_at=$10,
 start_time=$11, end_time=$12, updated_at=NOW()
WHERE id=$1
RETURNING id, player_id, player_name, status, total_score, questions_asked, questions_correct, hints_used,
 current_question_id, current_attempts, current_hint_used, question_started_at,
 start_time, end_time, created_at, updated_at`
	row := r.client.Pool.QueryRow(ctx, q,
		session.ID,
		string(session.Status),
		session.TotalScore,
		session.QuestionsAsked,
		session.QuestionsCorrect,
		session.HintsUsed,
		nullIfEmpty(session.CurrentQuestionID),
		session.CurrentAttempts,
		session.CurrentHintUsed,
		session.QuestionStartedAt,
		session.StartTime,
		session.EndTime,
	)
	updated, err := scanSession(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrSessionNotFound
		}
		return nil, err
	}
	return updated, nil
}

// CreateAttempt stores an answer attempt.
func (r *SessionRepository) CreateAttempt(ctx context.Context, attempt *domain.SessionAttempt) error {
	const q = `
INSERT INTO session_attempts
(id, session_id, question_id, attempt_number, provided_answer, is_correct, used_hint,
 awarded_score, latency_ms, created_at)
VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,NOW())`
	_, err := r.client.Pool.Exec(ctx, q,
		uuid.NewString(),
		attempt.SessionID,
		attempt.QuestionID,
		attempt.AttemptNumber,
		attempt.ProvidedAnswer,
		attempt.IsCorrect,
		attempt.UsedHint,
		attempt.AwardedScore,
		attempt.LatencyMs,
	)
	return err
}

// CreateEvent stores a session lifecycle or anti-cheat event.
func (r *SessionRepository) CreateEvent(ctx context.Context, event *domain.SessionEvent) error {
	metadata := strings.TrimSpace(event.Metadata)
	if metadata == "" {
		metadata = "{}"
	}
	const q = `
INSERT INTO session_events
(id, session_id, event_type, metadata_json, created_at)
VALUES ($1,$2,$3,$4::jsonb,NOW())`
	_, err := r.client.Pool.Exec(ctx, q,
		uuid.NewString(),
		event.SessionID,
		event.EventType,
		metadata,
	)
	return err
}

// ListQuestionIDsForSession lists unique question IDs already attempted in a session.
func (r *SessionRepository) ListQuestionIDsForSession(ctx context.Context, sessionID string) ([]string, error) {
	const q = `SELECT DISTINCT question_id FROM session_attempts WHERE session_id=$1 ORDER BY question_id ASC`
	rows, err := r.client.Pool.Query(ctx, q, sessionID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	ids := make([]string, 0)
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		ids = append(ids, id)
	}
	return ids, rows.Err()
}

func scanSession(scanner interface {
	Scan(dest ...interface{}) error
}) (*domain.GameSession, error) {
	var s domain.GameSession
	var status string
	var currentQuestionID *string
	if err := scanner.Scan(
		&s.ID,
		&s.PlayerID,
		&s.PlayerName,
		&status,
		&s.TotalScore,
		&s.QuestionsAsked,
		&s.QuestionsCorrect,
		&s.HintsUsed,
		&currentQuestionID,
		&s.CurrentAttempts,
		&s.CurrentHintUsed,
		&s.QuestionStartedAt,
		&s.StartTime,
		&s.EndTime,
		&s.CreatedAt,
		&s.UpdatedAt,
	); err != nil {
		return nil, err
	}
	s.Status = domain.Status(status)
	if currentQuestionID != nil {
		s.CurrentQuestionID = *currentQuestionID
	}
	return &s, nil
}

func nullIfEmpty(v string) interface{} {
	if strings.TrimSpace(v) == "" {
		return nil
	}
	return v
}

var _ domain.Repository = (*SessionRepository)(nil)