package main

import (
	"database/sql"
	"fmt"
	"os"
	"strings"
	"testing"
)

func TestReadMigrations(t *testing.T) {
	n := len(migrations)

	entries, err := os.ReadDir(migrationDir)
	if err != nil {
		t.Fatalf("Failed to determine number of migration files: %v", err)
	}
	nMigrationFiles := len(entries)

	if n != nMigrationFiles {
		t.Fatalf("Expected %d migration files but got %d.", nMigrationFiles, n)
	}

	for i, migration := range migrations {
		path := migrationPath(i)

		expectation := fmt.Sprintf("PRAGMA user_version = %d;", i+1)
		if !strings.HasPrefix(migration, expectation) {
			t.Fatalf("Expected '%s' at start of '%s'.", expectation, path)
		}
	}
}

func TestTransaction(t *testing.T) {
	db, _ := emptyDB(t)

	newVersion := 1
	err := Transaction(db, func(tx *sql.Tx) error {
		// valid statement
		_, err := tx.Exec(fmt.Sprintf("PRAGMA user_version = %d;", newVersion))
		if err != nil {
			return err
		}

		// invalid statement which should roll back the whole transaction
		_, err = tx.Exec("PRAGMA user_version THIS IS SYNTAX ERROR TALKING!!!")
		if err != nil {
			return err
		}
		return nil
	})
	if err == nil {
		t.Fatal("Error was not detected.")
	}

	version, err := UserVersion(db)
	if err != nil {
		t.Fatalf("Failed to get user_version: %v", err)
	}

	if version == newVersion {
		t.Fatal("Valid statement was not rolled back.")
	}

	expectedVersion := 0
	if version != expectedVersion {
		t.Fatalf("Expected user_version %d but got %d", expectedVersion, version)
	}
}

func TestMigrate(t *testing.T) {
	db, _ := emptyDB(t)

	userVersion, err := UserVersion(db)
	if err != nil {
		t.Fatalf("Failed to get initial user_version: %v", err)
	}

	if userVersion != 0 {
		t.Fatalf("Expected user_version 0 but got %d.", userVersion)
	}

	for i := range migrations {
		path := migrationPath(i)

		err := Migrate(db, i)
		if err != nil {
			t.Fatalf("Failed to execute migration %s: %v", path, err)
		}

		userVersion, err = UserVersion(db)
		if err != nil {
			t.Fatalf("Failed to get user_version after migration: %v", err)
		}

		expected := i + 1
		if userVersion != expected {
			t.Fatalf(
				"Expected user_version %d after running %s but got %d.",
				expected,
				path,
				userVersion,
			)
		}
	}
}

func TestUserVersion(t *testing.T) {
	db, _ := emptyDB(t)

	expectedVersion := 42
	err := Transaction(db, func(tx *sql.Tx) error {
		_, err := tx.Exec(fmt.Sprintf("PRAGMA user_version = %d;", expectedVersion))
		if err != nil {
			return err
		}
		return nil
	})
	if err != nil {
		t.Fatalf("Failed to set user expectedVersion: %v", err)
	}

	version, err := UserVersion(db)
	if err != nil {
		t.Fatalf("Could not execute function to test: %v", err)
	}

	if version != expectedVersion {
		t.Fatalf("Expected user_version %d but got %d.", expectedVersion, version)
	}
}

func TestMigrateToLatest(t *testing.T) {
	db, _ := emptyDB(t)

	err := MigrateToLatest(db)
	if err != nil {
		t.Fatalf("Could not execute function to test: %v", err)
	}

	v, err := UserVersion(db)
	if err != nil {
		t.Fatalf("Could not get user_version after migration: %v", err)
	}

	latest := len(migrations)
	if v != latest {
		t.Fatalf("Expected user_version %d but got %d.", latest, v)
	}

	futureUserVersion := 10000
	err = Transaction(db, func(tx *sql.Tx) error {
		_, err := tx.Exec(fmt.Sprintf("PRAGMA user_version = %d;", futureUserVersion))
		if err != nil {
			return err
		}
		return nil
	})

	err = MigrateToLatest(db)
	if err != nil {
		t.Fatalf("Could not execute function to test with future DB: %v", err)
	}

	v, err = UserVersion(db)
	if err != nil {
		t.Fatalf("Could not get user_version after migration with future DB: %v", err)
	}

	if v != futureUserVersion {
		t.Fatalf("Expected user_version %d but got %d.", futureUserVersion, v)
	}
}