package store

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

	_ "modernc.org/sqlite"
)

// openRawDB opens a SQLite DB at a fresh tempfile without running any
// migrations, so tests can observe migration-runner behaviour directly.
func openRawDB(t *testing.T) *sql.DB {
	t.Helper()
	path := filepath.Join(t.TempDir(), "state.db")
	dsn, err := sqliteDSN(path)
	if err != nil {
		t.Fatalf("sqliteDSN: %v", err)
	}
	db, err := sql.Open("sqlite", dsn)
	if err != nil {
		t.Fatalf("sql.Open: %v", err)
	}
	t.Cleanup(func() { _ = db.Close() })
	return db
}

func TestRunMigrationsAppliesBaselineOnFreshDB(t *testing.T) {
	db := openRawDB(t)
	if err := runMigrations(db); err != nil {
		t.Fatalf("runMigrations: %v", err)
	}
	// All declared migrations must be recorded.
	for _, m := range migrations {
		var got string
		if err := db.QueryRow("SELECT name FROM schema_migrations WHERE id = ?", m.id).Scan(&got); err != nil {
			t.Fatalf("migration %d not recorded: %v", m.id, err)
		}
		if got != m.name {
			t.Errorf("migration %d name = %q, want %q", m.id, got, m.name)
		}
	}
	// Baseline must have created the real tables.
	for _, table := range []string{"images", "vms"} {
		var name string
		if err := db.QueryRow("SELECT name FROM sqlite_master WHERE type='table' AND name=?", table).Scan(&name); err != nil {
			t.Fatalf("table %s missing: %v", table, err)
		}
	}
}

func TestRunMigrationsIsIdempotent(t *testing.T) {
	db := openRawDB(t)
	if err := runMigrations(db); err != nil {
		t.Fatalf("runMigrations first pass: %v", err)
	}
	if err := runMigrations(db); err != nil {
		t.Fatalf("runMigrations second pass: %v", err)
	}
	// One row per migration, no duplicates.
	var count int
	if err := db.QueryRow("SELECT COUNT(*) FROM schema_migrations").Scan(&count); err != nil {
		t.Fatalf("count: %v", err)
	}
	if count != len(migrations) {
		t.Errorf("schema_migrations rows = %d, want %d", count, len(migrations))
	}
}

func TestRunMigrationsSkipsAlreadyApplied(t *testing.T) {
	db := openRawDB(t)

	// Swap in a test-only migration whose body would error if invoked,
	// pre-insert its id into schema_migrations, and confirm the runner
	// recognises the marker and skips the body entirely.
	orig := migrations
	t.Cleanup(func() { migrations = orig })
	migrations = []migration{
		{id: 1, name: "baseline", up: migrateBaseline},
		{id: 99, name: "explodes-if-run", up: func(*sql.Tx) error {
			return errors.New("must not execute")
		}},
	}

	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		id INTEGER PRIMARY KEY,
		name TEXT NOT NULL,
		applied_at TEXT NOT NULL
	)`); err != nil {
		t.Fatalf("seed schema_migrations table: %v", err)
	}
	if _, err := db.Exec(
		"INSERT INTO schema_migrations (id, name, applied_at) VALUES (?, ?, ?)",
		99, "explodes-if-run", "2026-04-20T00:00:00Z",
	); err != nil {
		t.Fatalf("seed applied row: %v", err)
	}

	if err := runMigrations(db); err != nil {
		t.Fatalf("runMigrations: %v", err)
	}
}

func TestApplyMigrationRollsBackOnBodyError(t *testing.T) {
	db := openRawDB(t)
	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		id INTEGER PRIMARY KEY,
		name TEXT NOT NULL,
		applied_at TEXT NOT NULL
	)`); err != nil {
		t.Fatalf("seed schema_migrations: %v", err)
	}

	err := applyMigration(db, migration{
		id:   7,
		name: "creates-then-fails",
		up: func(tx *sql.Tx) error {
			if _, err := tx.Exec("CREATE TABLE transient (x INTEGER)"); err != nil {
				return err
			}
			return errors.New("synthetic failure")
		},
	})
	if err == nil {
		t.Fatal("expected applyMigration to surface body error")
	}

	// The transient table must NOT survive the failed migration.
	var name string
	if err := db.QueryRow("SELECT name FROM sqlite_master WHERE type='table' AND name='transient'").Scan(&name); err == nil {
		t.Fatal("transient table survived rollback")
	}
	// And no schema_migrations row for id=7.
	var count int
	if err := db.QueryRow("SELECT COUNT(*) FROM schema_migrations WHERE id=7").Scan(&count); err != nil {
		t.Fatalf("count: %v", err)
	}
	if count != 0 {
		t.Fatalf("schema_migrations recorded failed migration: count=%d", count)
	}
}

// TestMigrateDropDeadImageColumns_AcrossInstallPaths verifies the
// drop-column migration is correct on both paths it can land on:
// a fresh install (baseline created the column, migration 2 drops
// it) and a legacy DB that somehow lost or never had the column
// (migration 2 is a no-op). Runs migrations end-to-end so the
// invariant-check is the real system, not the helper in isolation.
func TestMigrateDropDeadImageColumns_AcrossInstallPaths(t *testing.T) {
	hasColumn := func(t *testing.T, db *sql.DB, table, column string) bool {
		t.Helper()
		rows, err := db.Query("PRAGMA table_info(" + table + ")")
		if err != nil {
			t.Fatalf("PRAGMA table_info: %v", err)
		}
		defer rows.Close()
		for rows.Next() {
			var (
				cid       int
				name      string
				valueType string
				notNull   int
				defaultV  sql.NullString
				pk        int
			)
			if err := rows.Scan(&cid, &name, &valueType, &notNull, &defaultV, &pk); err != nil {
				t.Fatalf("scan table_info row: %v", err)
			}
			if name == column {
				return true
			}
		}
		if err := rows.Err(); err != nil {
			t.Fatalf("rows.Err: %v", err)
		}
		return false
	}

	t.Run("fresh install drops packages_path", func(t *testing.T) {
		db := openRawDB(t)
		if err := runMigrations(db); err != nil {
			t.Fatalf("runMigrations: %v", err)
		}
		if hasColumn(t, db, "images", "packages_path") {
			t.Fatal("packages_path column survived migration 2 on fresh install")
		}
	})

	t.Run("legacy DB without column is a no-op", func(t *testing.T) {
		db := openRawDB(t)
		// Simulate a DB whose baseline was applied against a modified
		// schema that never had packages_path: seed schema_migrations,
		// run baseline, drop the column out-of-band, then run
		// runMigrations and expect migration 2 to succeed regardless.
		if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
			id INTEGER PRIMARY KEY,
			name TEXT NOT NULL,
			applied_at TEXT NOT NULL
		)`); err != nil {
			t.Fatalf("seed schema_migrations: %v", err)
		}
		if err := applyMigration(db, migrations[0]); err != nil {
			t.Fatalf("apply baseline: %v", err)
		}
		if _, err := db.Exec("ALTER TABLE images DROP COLUMN packages_path"); err != nil {
			t.Fatalf("pre-drop packages_path: %v", err)
		}
		if err := runMigrations(db); err != nil {
			t.Fatalf("runMigrations after manual pre-drop: %v", err)
		}
		if hasColumn(t, db, "images", "packages_path") {
			t.Fatal("packages_path reappeared after runMigrations")
		}
	})
}

// TestOpenReadOnlyDoesNotRunMigrations pins the doctor contract:
// OpenReadOnly must not mutate the DB. We create a DB without the
// schema_migrations row for migration 2 present (simulating a
// daemon-not-yet-run state), open it read-only, and confirm no row
// was added and no column dropped.
func TestOpenReadOnlyDoesNotRunMigrations(t *testing.T) {
	path := filepath.Join(t.TempDir(), "state.db")
	// Seed the file by running full Open once, then roll migration 2
	// backwards manually so the DB is "behind" current code.
	full, err := Open(path)
	if err != nil {
		t.Fatalf("Open: %v", err)
	}
	if _, err := full.db.Exec("ALTER TABLE images ADD COLUMN packages_path TEXT"); err != nil {
		t.Fatalf("re-add packages_path: %v", err)
	}
	if _, err := full.db.Exec("DELETE FROM schema_migrations WHERE id = 2"); err != nil {
		t.Fatalf("remove migration 2 marker: %v", err)
	}
	_ = full.Close()

	ro, err := OpenReadOnly(path)
	if err != nil {
		t.Fatalf("OpenReadOnly: %v", err)
	}
	defer ro.Close()

	// Migration 2 marker must still be absent; packages_path must
	// still exist.
	var migCount int
	if err := ro.db.QueryRow("SELECT COUNT(*) FROM schema_migrations WHERE id = 2").Scan(&migCount); err != nil {
		t.Fatalf("query schema_migrations: %v", err)
	}
	if migCount != 0 {
		t.Fatal("OpenReadOnly recorded migration 2 — the open path mutated the DB")
	}
	rows, err := ro.db.Query("PRAGMA table_info(images)")
	if err != nil {
		t.Fatalf("PRAGMA table_info: %v", err)
	}
	defer rows.Close()
	var sawColumn bool
	for rows.Next() {
		var (
			cid       int
			name      string
			valueType string
			notNull   int
			defaultV  sql.NullString
			pk        int
		)
		if err := rows.Scan(&cid, &name, &valueType, &notNull, &defaultV, &pk); err != nil {
			t.Fatalf("scan: %v", err)
		}
		if name == "packages_path" {
			sawColumn = true
		}
	}
	if !sawColumn {
		t.Fatal("packages_path disappeared — OpenReadOnly ran the drop migration")
	}
}

// TestOpenReadOnlyRefusesWrites confirms SQLite's mode=ro is in effect
// — no matter what a caller tries, writes are rejected at the driver
// level. Belt-and-braces guard against a future refactor that might
// plumb a write method through.
func TestOpenReadOnlyRefusesWrites(t *testing.T) {
	path := filepath.Join(t.TempDir(), "state.db")
	if s, err := Open(path); err != nil {
		t.Fatalf("seed Open: %v", err)
	} else {
		_ = s.Close()
	}
	ro, err := OpenReadOnly(path)
	if err != nil {
		t.Fatalf("OpenReadOnly: %v", err)
	}
	defer ro.Close()
	if _, err := ro.db.Exec("INSERT INTO schema_migrations (id, name, applied_at) VALUES (999, 'x', 'x')"); err == nil {
		t.Fatal("write succeeded against a read-only store")
	}
}

func TestRunMigrationsRejectsDuplicateID(t *testing.T) {
	db := openRawDB(t)
	orig := migrations
	t.Cleanup(func() { migrations = orig })
	migrations = []migration{
		{id: 1, name: "first", up: func(*sql.Tx) error { return nil }},
		{id: 1, name: "dupe", up: func(*sql.Tx) error { return nil }},
	}
	err := runMigrations(db)
	if err == nil {
		t.Fatal("expected error for duplicate migration id")
	}
}