package migrations_test

import (
	"database/sql"
	"path/filepath"
	"strings"
	"testing"
	"testing/fstest"

	_ "modernc.org/sqlite"

	"github.com/dariuszjaniak/warp/server/internal/storage/migrations"
)

var dialect = migrations.Dialect{
	Name: "sqlite",
	CreateTable: `CREATE TABLE IF NOT EXISTS schema_migrations (
		version INTEGER PRIMARY KEY, name TEXT NOT NULL,
		checksum TEXT NOT NULL, applied_at TIMESTAMP NOT NULL)`,
	SelectApplied: `SELECT version, name, checksum, applied_at FROM schema_migrations ORDER BY version`,
	InsertApplied: `INSERT INTO schema_migrations (version, name, checksum, applied_at) VALUES (?, ?, ?, ?)`,
}

func openDB(t *testing.T) *sql.DB {
	t.Helper()
	path := filepath.ToSlash(filepath.Join(t.TempDir(), "test.db"))
	db, err := sql.Open("sqlite", "file:"+path)
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = db.Close() })
	return db
}

func fsWith(files map[string]string) fstest.MapFS {
	out := fstest.MapFS{}
	for name, body := range files {
		out["migrations/"+name] = &fstest.MapFile{Data: []byte(body)}
	}
	return out
}

func TestLoadOrdersByVersionAndParsesNames(t *testing.T) {
	ms, err := migrations.Load(fsWith(map[string]string{
		"0002_devices.sql":         "CREATE TABLE devices (id TEXT);",
		"0001_server_settings.sql": "CREATE TABLE server_settings (k TEXT);",
		"notes.txt":                "ignored",
	}), "migrations")
	if err != nil {
		t.Fatalf("Load: %v", err)
	}
	if len(ms) != 2 {
		t.Fatalf("loaded %d migrations, want 2", len(ms))
	}
	if ms[0].Version != 1 || ms[0].Name != "server_settings" {
		t.Errorf("first migration = %d/%s", ms[0].Version, ms[0].Name)
	}
	if ms[1].Version != 2 || ms[1].Name != "devices" {
		t.Errorf("second migration = %d/%s", ms[1].Version, ms[1].Name)
	}
	if ms[0].Checksum == "" || ms[0].Checksum == ms[1].Checksum {
		t.Error("each migration needs its own checksum")
	}
}

func TestLoadRejectsBadFilenames(t *testing.T) {
	for _, name := range []string{"nope.sql", "abc_x.sql", "0000_zero.sql"} {
		if _, err := migrations.Load(fsWith(map[string]string{name: "SELECT 1;"}), "migrations"); err == nil {
			t.Errorf("Load(%s) = nil error, want a complaint", name)
		}
	}
}

func TestRunIsIdempotent(t *testing.T) {
	db := openDB(t)
	fsys := fsWith(map[string]string{
		"0001_server_settings.sql": "CREATE TABLE server_settings (k TEXT PRIMARY KEY);",
	})
	ms, err := migrations.Load(fsys, "migrations")
	if err != nil {
		t.Fatal(err)
	}

	n, err := migrations.Run(t.Context(), db, dialect, ms, nil)
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	if n != 1 {
		t.Errorf("applied %d migrations, want 1", n)
	}

	n, err = migrations.Run(t.Context(), db, dialect, ms, nil)
	if err != nil {
		t.Fatalf("second Run: %v", err)
	}
	if n != 0 {
		t.Errorf("second Run applied %d migrations, want 0", n)
	}
}

func TestRunDetectsEditedMigration(t *testing.T) {
	db := openDB(t)
	before, err := migrations.Load(fsWith(map[string]string{
		"0001_server_settings.sql": "CREATE TABLE server_settings (k TEXT PRIMARY KEY);",
	}), "migrations")
	if err != nil {
		t.Fatal(err)
	}
	if _, err := migrations.Run(t.Context(), db, dialect, before, nil); err != nil {
		t.Fatal(err)
	}

	after, err := migrations.Load(fsWith(map[string]string{
		"0001_server_settings.sql": "CREATE TABLE server_settings (k TEXT PRIMARY KEY, v TEXT);",
	}), "migrations")
	if err != nil {
		t.Fatal(err)
	}
	_, err = migrations.Run(t.Context(), db, dialect, after, nil)
	if err == nil {
		t.Fatal("expected an error for an edited migration")
	}
	if !strings.Contains(err.Error(), "has changed since it was applied") {
		t.Errorf("unhelpful error: %v", err)
	}
}

func TestRunRollsBackFailedMigration(t *testing.T) {
	db := openDB(t)
	ms, err := migrations.Load(fsWith(map[string]string{
		"0001_ok.sql":     "CREATE TABLE a (k TEXT);",
		"0002_broken.sql": "CREATE TABLE b (k TEXT); THIS IS NOT SQL;",
	}), "migrations")
	if err != nil {
		t.Fatal(err)
	}

	n, err := migrations.Run(t.Context(), db, dialect, ms, nil)
	if err == nil {
		t.Fatal("expected the broken migration to fail")
	}
	if n != 1 {
		t.Errorf("applied %d migrations before failing, want 1", n)
	}

	// The failed migration must leave nothing behind.
	var count int
	if err := db.QueryRowContext(t.Context(),
		`SELECT count(*) FROM sqlite_master WHERE type = 'table' AND name = 'b'`).Scan(&count); err != nil {
		t.Fatal(err)
	}
	if count != 0 {
		t.Error("table from the failed migration was not rolled back")
	}

	pending, err := migrations.Pending(t.Context(), db, dialect, ms)
	if err != nil {
		t.Fatal(err)
	}
	if len(pending) != 1 || pending[0].Version != 2 {
		t.Errorf("pending = %v, want just migration 2", pending)
	}
}

func TestCheckNotAhead(t *testing.T) {
	applied := []migrations.Applied{{Version: 7, Name: "future"}}
	ms := []migrations.Migration{{Version: 1, Name: "server_settings"}}

	if err := migrations.CheckNotAhead(applied, ms); err == nil {
		t.Fatal("expected a dirty-schema error")
	}
	if err := migrations.CheckNotAhead(nil, ms); err != nil {
		t.Errorf("fresh database must be fine, got %v", err)
	}
}