package db_test

import (
	"context"
	"errors"
	"net/url"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"go.uber.org/fx/fxtest"
	"sneak.berlin/go/neoirc/internal/config"
	"sneak.berlin/go/neoirc/internal/db"
	"sneak.berlin/go/neoirc/internal/globals"
	"sneak.berlin/go/neoirc/internal/logger"
)

const wantBusyTimeoutMS = 5000

const (
	// endlessQuery counts the rows of a recursive query that never
	// stops, so it runs until its context ends.
	endlessQuery = `WITH RECURSIVE n(x) AS
		(SELECT 1 UNION ALL SELECT x + 1 FROM n)
		SELECT COUNT(*) FROM n`

	endlessQueryTimeout = 100 * time.Millisecond
)

// TestDefaultDBURLSetsWALAndBusyTimeout opens a file database
// with the default URL's parameters the way the server does,
// and checks the journal mode and busy timeout it ends up with.
func TestDefaultDBURLSetsWALAndBusyTimeout(t *testing.T) {
	t.Parallel()

	_, params, _ := strings.Cut(config.DefaultDBURL, "?")
	dbURL := "file://" + filepath.Join(t.TempDir(), "state.db") +
		"?" + params

	lifecycle := fxtest.NewLifecycle(t)

	log, err := logger.New(lifecycle, logger.Params{
		Globals: &globals.Globals{},
	})
	if err != nil {
		t.Fatal(err)
	}

	database, err := db.New(lifecycle, db.Params{
		Logger: log,
		Config: &config.Config{DBURL: dbURL},
	})
	if err != nil {
		t.Fatal(err)
	}

	lifecycle.RequireStart()
	t.Cleanup(lifecycle.RequireStop)

	var journalMode string

	err = database.GetDB().QueryRowContext(
		t.Context(), "PRAGMA journal_mode",
	).Scan(&journalMode)
	if err != nil {
		t.Fatal(err)
	}

	if journalMode != "wal" {
		t.Errorf("journal_mode = %q, want %q", journalMode, "wal")
	}

	var busyTimeout int

	err = database.GetDB().QueryRowContext(
		t.Context(), "PRAGMA busy_timeout",
	).Scan(&busyTimeout)
	if err != nil {
		t.Fatal(err)
	}

	if busyTimeout != wantBusyTimeoutMS {
		t.Errorf(
			"busy_timeout = %d, want %d",
			busyTimeout, wantBusyTimeoutMS,
		)
	}
}

// TestForeignKeysOnAfterCancelledQuery cancels a query while it
// runs, which makes the pool close its only connection and open a
// new one. A TEMP table lasts only as long as its connection, so
// its absence shows the connection was replaced. The test then
// checks that the file database keeps its tables and that the new
// connection has foreign keys on.
func TestForeignKeysOnAfterCancelledQuery(t *testing.T) {
	t.Parallel()

	_, defaultParams, _ := strings.Cut(config.DefaultDBURL, "?")

	urlParams := map[string]string{
		"default parameters": "?" + defaultParams,
		"no parameters":      "",
	}

	for name, params := range urlParams {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			dbURL := "file://" +
				filepath.Join(t.TempDir(), "state.db") + params

			database, err := startDatabase(t, dbURL)
			if err != nil {
				t.Fatal(err)
			}

			_, err = database.GetDB().ExecContext(
				t.Context(), "CREATE TEMP TABLE first_connection (x)",
			)
			if err != nil {
				t.Fatal(err)
			}

			ctx, cancel := context.WithTimeout(
				t.Context(), endlessQueryTimeout,
			)
			defer cancel()

			_, err = database.GetDB().ExecContext(ctx, endlessQuery)
			if !errors.Is(err, context.DeadlineExceeded) {
				t.Fatalf("endless query: err = %v", err)
			}

			tempTables := queryInt(
				t, database, "SELECT COUNT(*) FROM sqlite_temp_schema",
			)
			if tempTables != 0 {
				t.Fatal("the pool kept its first connection")
			}

			migrations := queryInt(
				t, database, "SELECT COUNT(*) FROM schema_migrations",
			)
			if migrations == 0 {
				t.Error("schema_migrations is empty")
			}

			foreignKeys := queryInt(t, database, "PRAGMA foreign_keys")
			if foreignKeys != 1 {
				t.Errorf("foreign_keys = %d, want 1", foreignKeys)
			}
		})
	}
}

// TestDBURLSettingForeignKeysFailsStartup checks that the database
// refuses to start when DBURL sets foreign_keys itself, however it
// is spelled.
func TestDBURLSettingForeignKeysFailsStartup(t *testing.T) {
	t.Parallel()

	pragmas := []string{
		"foreign_keys(0)",
		"foreign_keys(off)",
		"foreign_keys=0",
		"FOREIGN_KEYS(FALSE)",
		" Foreign_Keys = 1",
	}

	for _, pragma := range pragmas {
		t.Run(pragma, func(t *testing.T) {
			t.Parallel()

			dbURL := "file://" +
				filepath.Join(t.TempDir(), "state.db") +
				"?_pragma=" + url.QueryEscape(pragma)

			_, err := startDatabase(t, dbURL)
			if err == nil {
				t.Fatal("the database started")
			}

			if !strings.Contains(err.Error(), "DBURL") {
				t.Errorf("error %q does not name DBURL", err)
			}
		})
	}
}

// startDatabase starts a Database for dbURL the way the server does.
// It returns the error that stopped it from starting, if any.
func startDatabase(t *testing.T, dbURL string) (*db.Database, error) {
	t.Helper()

	lifecycle := fxtest.NewLifecycle(t)

	log, err := logger.New(lifecycle, logger.Params{
		Globals: &globals.Globals{},
	})
	if err != nil {
		t.Fatal(err)
	}

	database, err := db.New(lifecycle, db.Params{
		Logger: log,
		Config: &config.Config{DBURL: dbURL},
	})
	if err != nil {
		t.Fatal(err)
	}

	t.Cleanup(lifecycle.RequireStop)

	return database, lifecycle.Start(t.Context())
}

// queryInt runs a query that returns a single number.
func queryInt(t *testing.T, database *db.Database, query string) int {
	t.Helper()

	var result int

	err := database.GetDB().QueryRowContext(t.Context(), query).Scan(&result)
	if err != nil {
		t.Fatal(err)
	}

	return result
}