package mdb

import (
	"errors"
	"net/http"
	"net/http/httptest"
	"reflect"
	"testing"
	"time"
)

func TestDBRunTests(t *testing.T) {
	t.Helper()
	for _, testCase := range testDBTestCases {
		testCase := testCase
		t.Run(testCase.Name, func(t *testing.T) {
			t.Parallel()
			testRunner_testCase(t, testCase)
		})
	}
}

func testRunner_testCase(t *testing.T, testCase DBTestCase) {
	rootDir := t.TempDir()
	db := NewTestDBPrimary(t, rootDir)

	mux := http.NewServeMux()
	mux.HandleFunc("/rep/", db.Handle)
	testServer := httptest.NewServer(mux)
	defer testServer.Close()

	rootDir2 := t.TempDir()
	db2 := NewTestSecondaryDB(t, rootDir2, testServer.URL+"/rep/")
	defer db2.Close()

	snapshots := make([]*Snapshot, 0, len(testCase.Steps))

	// Run each step and it's associated check function.
	for _, step := range testCase.Steps {
		t.Run(step.Name, func(t *testing.T) {
			err := db.Update(func(tx *Snapshot) error {
				return step.Update(t, db, tx)
			})

			if !errors.Is(err, step.ExpectedUpdateError) {
				t.Fatal(err, step.ExpectedUpdateError)
			}

			snapshot := db.Snapshot()
			snapshots = append(snapshots, snapshot)

			testRunner_checkState(t, db, snapshot, step.State)
		})
	}

	// Run each step's check function again with stored snapshot.
	for i, step := range testCase.Steps {
		snapshot := snapshots[i]
		t.Run(step.Name+"-checkSnapshot", func(t *testing.T) {
			testRunner_checkState(t, db, snapshot, step.State)
		})
	}

	pInfo := db.Info()

	for {
		info := db2.Info()
		if info.SeqNum == pInfo.SeqNum {
			break
		}
		time.Sleep(time.Millisecond)
	}

	// TODO: Why is this necessary?
	time.Sleep(time.Second)
	finalStep := testCase.Steps[len(testCase.Steps)-1]

	secondarySnapshot := db2.Snapshot()
	t.Run("Check secondary", func(t *testing.T) {
		testRunner_checkState(t, db2, secondarySnapshot, finalStep.State)
	})

	if err := db.Close(); err != nil {
		t.Fatal(err)
	}

	db = NewTestDBPrimary(t, rootDir)
	snapshot := db.Snapshot()

	// Run the final step's check function again with a newly loaded db.
	t.Run("Check after reload", func(t *testing.T) {
		testRunner_checkState(t, db, snapshot, finalStep.State)
	})

	t.Run("Check that primary and secondary are equal", func(t *testing.T) {
		db.AssertEqual(t, db2.Database)
	})

	db.Close()
}

func testRunner_checkState(
	t *testing.T,
	db TestDB,
	tx *Snapshot,
	state DBState,
) {
	t.Helper()
	checkSlicesEqual(t, "UsersByID", db.Users.ByID.Dump(tx), state.UsersByID)
	checkSlicesEqual(t, "UsersByEmail", db.Users.ByEmail.Dump(tx), state.UsersByEmail)
	checkSlicesEqual(t, "UsersByName", db.Users.ByName.Dump(tx), state.UsersByName)
	checkSlicesEqual(t, "UsersByBlocked", db.Users.ByBlocked.Dump(tx), state.UsersByBlocked)
	checkSlicesEqual(t, "DataByID", db.UserData.ByID.Dump(tx), state.DataByID)
	checkSlicesEqual(t, "DataByName", db.UserData.ByName.Dump(tx), state.DataByName)

	checkMinMaxEqual(t, "UsersByID", tx, db.Users.ByID, state.UsersByID)
	checkMinMaxEqual(t, "UsersByEmail", tx, db.Users.ByEmail, state.UsersByEmail)
	checkMinMaxEqual(t, "UsersByName", tx, db.Users.ByName, state.UsersByName)
	checkMinMaxEqual(t, "UsersByBlocked", tx, db.Users.ByBlocked, state.UsersByBlocked)
	checkMinMaxEqual(t, "DataByID", tx, db.UserData.ByID, state.DataByID)
	checkMinMaxEqual(t, "DataByName", tx, db.UserData.ByName, state.DataByName)
}

func checkSlicesEqual[T any](t *testing.T, name string, actual, expected []T) {
	t.Helper()
	if len(actual) != len(expected) {
		t.Fatal(name, len(actual), len(expected))
	}

	for i := range actual {
		if !reflect.DeepEqual(actual[i], expected[i]) {
			t.Fatal(name, actual[i], expected[i])
		}
	}
}

func checkMinMaxEqual[T any](t *testing.T, name string, tx *Snapshot, index *Index[T], expected []T) {
	if len(expected) == 0 {
		if min := index.Min(tx); min != nil {
			t.Fatal(min)
		}
		if max := index.Max(tx); max != nil {
			t.Fatal(max)
		}
		return
	}

	min := index.Min(tx)
	if min == nil {
		t.Fatal("No min")
	}
	max := index.Max(tx)
	if max == nil {
		t.Fatal("No max")
	}

	if !reflect.DeepEqual(*min, expected[0]) {
		t.Fatal(min, expected[0])
	}

	if !reflect.DeepEqual(*max, expected[len(expected)-1]) {
		t.Fatal(max)
	}
}