package store_test

import (
	"database/sql"
	"errors"
	"path/filepath"
	"testing"
	"time"

	"github.com/golang-migrate/migrate/v4"
	migratesqlite "github.com/golang-migrate/migrate/v4/database/sqlite"
	"github.com/golang-migrate/migrate/v4/source/iofs"

	"github.com/wangjia/pangolin/server/internal/config"
	"github.com/wangjia/pangolin/server/internal/store"
	"github.com/wangjia/pangolin/server/migrations"
)

// migratorAt builds a golang-migrate instance against a file-backed SQLite DB
// and steps it to exactly `version` (unlike store.MigrateUp/Down, which always
// target head/0). This is Task 8 Step 2's upgrade rehearsal: a real file DB
// (not :memory:) simulating a production sqlite store carrying pre-000021 rows
// through the 000021 subscriptions-table rebuild.
func migratorAt(t *testing.T, database *sql.DB, version uint) {
	t.Helper()
	src, err := iofs.New(migrations.SQLiteFS, "sqlite")
	if err != nil {
		t.Fatalf("iofs source: %v", err)
	}
	defer src.Close()

	mdriver, err := migratesqlite.WithInstance(database, &migratesqlite.Config{})
	if err != nil {
		t.Fatalf("sqlite migrate driver: %v", err)
	}

	m, err := migrate.NewWithInstance("iofs", src, "sqlite", mdriver)
	if err != nil {
		t.Fatalf("new migrator: %v", err)
	}

	if err := m.Migrate(version); err != nil && !errors.Is(err, migrate.ErrNoChange) {
		t.Fatalf("migrate to version %d: %v", version, err)
	}
}

// insertLegacySubRow inserts one subscriptions row with a pre-000021 source
// value ('trial' or 'code') for a fresh user, returning the assigned user_id
// and subscription id.
func insertLegacySubRow(t *testing.T, database *sql.DB, uuidSuffix, source string) (userID, subID int64) {
	t.Helper()

	res, err := database.Exec(
		`INSERT INTO users (uuid, email, pw_hash, dp_uuid, status) VALUES (?, ?, 'x', ?, 'active')`,
		"u-"+uuidSuffix, uuidSuffix+"@example.com", "dp-"+uuidSuffix,
	)
	if err != nil {
		t.Fatalf("insert user(%s): %v", source, err)
	}
	userID, err = res.LastInsertId()
	if err != nil {
		t.Fatalf("user LastInsertId: %v", err)
	}

	var planID int64
	if err := database.QueryRow(`SELECT id FROM plans WHERE code = 'pro'`).Scan(&planID); err != nil {
		t.Fatalf("lookup pro plan id: %v", err)
	}

	res, err = database.Exec(
		`INSERT INTO subscriptions (user_id, plan_id, expires_at, source) VALUES (?, ?, ?, ?)`,
		userID, planID, time.Now().Add(30*24*time.Hour).UTC().Format("2006-01-02 15:04:05"), source,
	)
	if err != nil {
		t.Fatalf("insert subscription(source=%s): %v", source, err)
	}
	subID, err = res.LastInsertId()
	if err != nil {
		t.Fatalf("subscription LastInsertId: %v", err)
	}
	return userID, subID
}

// TestSQLitePayMigrationRehearsal_UpgradeWithData is Task 8 Step 2: rehearse
// the 000021 upgrade (subscriptions table rebuild for source='pay') against a
// file-backed SQLite DB pre-loaded with real 'trial'/'code' rows, and assert
// no rows are lost and the id/AUTOINCREMENT sequence is preserved.
func TestSQLitePayMigrationRehearsal_UpgradeWithData(t *testing.T) {
	dsn := filepath.Join(t.TempDir(), "pay_upgrade_rehearsal.db")
	database, err := store.Open(&config.Config{Driver: "sqlite", DSN: dsn})
	if err != nil {
		t.Fatalf("store.Open: %v", err)
	}
	defer database.Close()

	// 1. Up to 000020 (pre-pay baseline; plans already seeded by 000007).
	migratorAt(t, database, 20)

	trialUserID, trialSubID := insertLegacySubRow(t, database, "trial1", "trial")
	codeUserID, codeSubID := insertLegacySubRow(t, database, "code1", "code")
	_ = trialUserID
	_ = codeUserID

	// 2. Up to 000021 — subscriptions_new rebuild + pay_purchases creation.
	migratorAt(t, database, 21)

	v, dirty, err := store.MigrateVersion(database, "sqlite")
	if err != nil {
		t.Fatalf("MigrateVersion: %v", err)
	}
	if dirty || v != 21 {
		t.Fatalf("after up to 21: version=%d dirty=%v, want 21/false", v, dirty)
	}

	// 3. Row count and ids preserved across the rebuild.
	var count int
	if err := database.QueryRow(`SELECT COUNT(*) FROM subscriptions`).Scan(&count); err != nil {
		t.Fatalf("count subscriptions: %v", err)
	}
	if count != 2 {
		t.Errorf("subscriptions count after 000021 = %d, want 2 (rows lost in rebuild)", count)
	}

	for _, want := range []struct {
		id     int64
		source string
	}{{trialSubID, "trial"}, {codeSubID, "code"}} {
		var gotSource string
		if err := database.QueryRow(`SELECT source FROM subscriptions WHERE id = ?`, want.id).Scan(&gotSource); err != nil {
			t.Errorf("subscription id=%d missing after 000021: %v", want.id, err)
			continue
		}
		if gotSource != want.source {
			t.Errorf("subscription id=%d source = %q, want %q", want.id, gotSource, want.source)
		}
	}

	// 4. New source='pay' value now accepted, and AUTOINCREMENT continues
	// (not reset to 1 by the table rebuild).
	var planID int64
	if err := database.QueryRow(`SELECT id FROM plans WHERE code = 'pro'`).Scan(&planID); err != nil {
		t.Fatalf("lookup pro plan id: %v", err)
	}
	res, err := database.Exec(
		`INSERT INTO subscriptions (user_id, plan_id, expires_at, source) VALUES (?, ?, ?, 'pay')`,
		trialUserID, planID, time.Now().Add(30*24*time.Hour).UTC().Format("2006-01-02 15:04:05"),
	)
	if err != nil {
		t.Fatalf("insert source='pay' subscription after 000021: %v", err)
	}
	paySubID, err := res.LastInsertId()
	if err != nil {
		t.Fatalf("pay subscription LastInsertId: %v", err)
	}
	if paySubID <= codeSubID {
		t.Errorf("pay subscription id=%d did not continue AUTOINCREMENT sequence (prior max id=%d)", paySubID, codeSubID)
	}

	// 5. pay_purchases table exists and is empty (fresh table from 000021).
	var payCount int
	if err := database.QueryRow(`SELECT COUNT(*) FROM pay_purchases`).Scan(&payCount); err != nil {
		t.Fatalf("count pay_purchases (table should exist post-000021): %v", err)
	}
	if payCount != 0 {
		t.Errorf("pay_purchases count = %d, want 0 (fresh table)", payCount)
	}
}

// TestSQLitePayMigrationRehearsal_DownUpIdempotent covers the second half of
// Task 8 Step 2: with only pre-000021 ('trial'/'code') data present, down
// (rollback 000021) then up (re-apply) must be idempotent and lossless.
//
// It also documents an intentional safety property: once a source='pay' row
// exists, 000021's down.sql (which rebuilds subscriptions with the stricter
// CHECK (source IN ('trial','code'))) correctly REFUSES to downgrade rather
// than silently dropping paid-subscription rows — see the trailing assertion.
func TestSQLitePayMigrationRehearsal_DownUpIdempotent(t *testing.T) {
	dsn := filepath.Join(t.TempDir(), "pay_downup_rehearsal.db")
	database, err := store.Open(&config.Config{Driver: "sqlite", DSN: dsn})
	if err != nil {
		t.Fatalf("store.Open: %v", err)
	}
	defer database.Close()

	migratorAt(t, database, 20)
	_, trialSubID := insertLegacySubRow(t, database, "trial2", "trial")
	_, codeSubID := insertLegacySubRow(t, database, "code2", "code")

	migratorAt(t, database, 21)

	// down: 000021 -> 000020. No 'pay' rows exist yet, so this must succeed
	// and preserve the trial/code rows with their original ids.
	migratorAt(t, database, 20)

	v, dirty, err := store.MigrateVersion(database, "sqlite")
	if err != nil {
		t.Fatalf("MigrateVersion after down: %v", err)
	}
	if dirty || v != 20 {
		t.Fatalf("after down to 20: version=%d dirty=%v, want 20/false", v, dirty)
	}

	var count int
	if err := database.QueryRow(`SELECT COUNT(*) FROM subscriptions`).Scan(&count); err != nil {
		t.Fatalf("count subscriptions after down: %v", err)
	}
	if count != 2 {
		t.Errorf("subscriptions count after down to 000020 = %d, want 2 (rows lost on downgrade)", count)
	}
	for _, id := range []int64{trialSubID, codeSubID} {
		var exists int
		if err := database.QueryRow(`SELECT COUNT(*) FROM subscriptions WHERE id = ?`, id).Scan(&exists); err != nil || exists != 1 {
			t.Errorf("subscription id=%d missing after down to 000020 (err=%v)", id, err)
		}
	}
	var hasPayTable int
	err = database.QueryRow(`SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name='pay_purchases'`).Scan(&hasPayTable)
	if err != nil || hasPayTable != 0 {
		t.Errorf("pay_purchases table still present after down to 000020 (err=%v)", err)
	}

	// up: 000020 -> 000021 again — idempotent re-apply, same rows/ids.
	migratorAt(t, database, 21)
	v, dirty, err = store.MigrateVersion(database, "sqlite")
	if err != nil {
		t.Fatalf("MigrateVersion after re-up: %v", err)
	}
	if dirty || v != 21 {
		t.Fatalf("after re-up to 21: version=%d dirty=%v, want 21/false", v, dirty)
	}
	if err := database.QueryRow(`SELECT COUNT(*) FROM subscriptions`).Scan(&count); err != nil {
		t.Fatalf("count subscriptions after re-up: %v", err)
	}
	if count != 2 {
		t.Errorf("subscriptions count after down+up cycle = %d, want 2", count)
	}

	// Safety-net documentation: once a source='pay' row exists, down must be
	// refused (CHECK (source IN ('trial','code')) on the down-rebuilt table),
	// not silently drop it. This is NOT a bug — see 000021.down.sql.
	var planID int64
	if err := database.QueryRow(`SELECT id FROM plans WHERE code = 'pro'`).Scan(&planID); err != nil {
		t.Fatalf("lookup pro plan id: %v", err)
	}
	var uid int64
	if err := database.QueryRow(`SELECT user_id FROM subscriptions WHERE id = ?`, trialSubID).Scan(&uid); err != nil {
		t.Fatalf("lookup trial subscription user_id: %v", err)
	}
	if _, err := database.Exec(
		`INSERT INTO subscriptions (user_id, plan_id, expires_at, source) VALUES (?, ?, ?, 'pay')`,
		uid, planID, time.Now().Add(30*24*time.Hour).UTC().Format("2006-01-02 15:04:05"),
	); err != nil {
		t.Fatalf("insert source='pay' subscription: %v", err)
	}

	src, err := iofs.New(migrations.SQLiteFS, "sqlite")
	if err != nil {
		t.Fatalf("iofs source: %v", err)
	}
	defer src.Close()
	mdriver, err := migratesqlite.WithInstance(database, &migratesqlite.Config{})
	if err != nil {
		t.Fatalf("sqlite migrate driver: %v", err)
	}
	m, err := migrate.NewWithInstance("iofs", src, "sqlite", mdriver)
	if err != nil {
		t.Fatalf("new migrator: %v", err)
	}
	downErr := m.Migrate(20)
	if downErr == nil {
		t.Error("expected down to 000020 to FAIL once a source='pay' row exists " +
			"(subscriptions_old CHECK (source IN ('trial','code'))); it succeeded instead " +
			"— either the safety property regressed or a 'pay' row was silently dropped")
	} else {
		t.Logf("down to 000020 correctly refused with a source='pay' row present: %v", downErr)
	}
	// This DB file (and any dirty migration-version bookkeeping from the
	// refused down above) is discarded with t.TempDir() at test end.
}