package mdb

import (
	"errors"
	"fmt"
	"reflect"
	"strings"
	"testing"

	"git.crumpington.com/public/jldb/lib/errs"
)

type DBTestCase struct {
	Name  string
	Steps []DBTestStep
}

type DBTestStep struct {
	Name                string
	Update              func(t *testing.T, db TestDB, tx *Snapshot) error
	ExpectedUpdateError error
	State               DBState
}

type DBState struct {
	UsersByID      []User
	UsersByEmail   []User
	UsersByName    []User
	UsersByBlocked []User
	DataByID       []UserDataItem
	DataByName     []UserDataItem
}

var testDBTestCases = []DBTestCase{{

	Name: "Insert update",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {

		Name: "Update",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := db.Users.ByID.Get(tx, &User{ID: 1})
			if user == nil {
				return errs.NotFound
			}
			user.Name = "Bob"
			user.Email = "b@c.com"
			return db.Users.Update(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Bob", Email: "b@c.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Bob", Email: "b@c.com"}},
			UsersByName:  []User{{ID: 1, Name: "Bob", Email: "b@c.com"}},
		},
	}},
}, {

	Name: "Insert delete",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {

		Name: "Delete",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			return db.Users.Delete(tx, 1)
		},

		State: DBState{},
	}},
}, {

	Name: "Insert duplicate one tx (ID)",

	Steps: []DBTestStep{{
		Name: "Insert with duplicate",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			if err := db.Users.Insert(tx, user); err != nil {
				return err
			}
			user2 := &User{ID: 1, Name: "Bob", Email: "b@c.com"}
			return db.Users.Insert(tx, user2)
		},

		ExpectedUpdateError: errs.Duplicate,

		State: DBState{},
	}},
}, {

	Name: "Insert duplicate one tx (email)",

	Steps: []DBTestStep{{
		Name: "Insert with duplicate",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			if err := db.Users.Insert(tx, user); err != nil {
				return err
			}
			user2 := &User{ID: 2, Name: "Bob", Email: "a@b.com"}
			return db.Users.Insert(tx, user2)
		},

		ExpectedUpdateError: errs.Duplicate,

		State: DBState{},
	}},
}, {

	Name: "Insert duplicate two txs (ID)",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {

		Name: "Insert duplicate",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Bob", Email: "b@c.com"}
			return db.Users.Insert(tx, user)
		},

		ExpectedUpdateError: errs.Duplicate,

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Insert duplicate two txs (email)",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {

		Name: "Insert duplicate",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 2, Name: "Bob", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		ExpectedUpdateError: errs.Duplicate,

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Insert read-only snapshot",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(db.Snapshot(), user)
		},

		ExpectedUpdateError: errs.ReadOnly,
	}},
}, {

	Name: "Insert partial index",

	Steps: []DBTestStep{{

		Name: "Insert Alice",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 5, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Insert Bob",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 2, Name: "Bob", Email: "b@c.com", Blocked: true}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID: []User{
				{ID: 2, Name: "Bob", Email: "b@c.com", Blocked: true},
				{ID: 5, Name: "Alice", Email: "a@b.com"},
			},
			UsersByEmail: []User{
				{ID: 5, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com", Blocked: true},
			},
			UsersByName: []User{
				{ID: 5, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com", Blocked: true},
			},
			UsersByBlocked: []User{
				{ID: 2, Name: "Bob", Email: "b@c.com", Blocked: true},
			},
		},
	}},
}, {

	Name: "Update not found",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 5, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Update",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 4, Name: "Alice", Email: "x@y.com"}
			return db.Users.Update(tx, user)
		},

		ExpectedUpdateError: errs.NotFound,

		State: DBState{
			UsersByID:    []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 5, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Update read-only snapshot",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {

		Name: "Update",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := db.Users.ByID.Get(tx, &User{ID: 1})
			if user == nil {
				return errs.NotFound
			}
			user.Name = "Bob"
			user.Email = "b@c.com"
			return db.Users.Update(db.Snapshot(), user)
		},

		ExpectedUpdateError: errs.ReadOnly,

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Insert into two collections",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			if err := db.Users.Insert(tx, user); err != nil {
				return err
			}
			data := &UserDataItem{ID: 1, UserID: user.ID, Name: "Item1", Data: "xyz"}
			return db.UserData.Insert(tx, data)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			DataByID:     []UserDataItem{{ID: 1, UserID: 1, Name: "Item1", Data: "xyz"}},
			DataByName:   []UserDataItem{{ID: 1, UserID: 1, Name: "Item1", Data: "xyz"}},
		},
	}},
}, {

	Name: "Update into index",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Update",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}
			return db.Users.Update(tx, user)
		},

		State: DBState{
			UsersByID:      []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
			UsersByEmail:   []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
			UsersByName:    []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
			UsersByBlocked: []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
		},
	}},
}, {

	Name: "Update out of index",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:      []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
			UsersByEmail:   []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
			UsersByName:    []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
			UsersByBlocked: []User{{ID: 1, Name: "Alice", Email: "a@b.com", Blocked: true}},
		},
	}, {
		Name: "Update",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Update(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Update duplicate one tx",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user1 := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			if err := db.Users.Insert(tx, user1); err != nil {
				return err
			}
			user2 := &User{ID: 2, Name: "Bob", Email: "b@c.com"}
			if err := db.Users.Insert(tx, user2); err != nil {
				return err
			}

			user2.Email = "a@b.com"
			return db.Users.Update(tx, user2)
		},

		ExpectedUpdateError: errs.Duplicate,

		State: DBState{},
	}},
}, {

	Name: "Update duplicate two txs",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user1 := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			if err := db.Users.Insert(tx, user1); err != nil {
				return err
			}
			user2 := &User{ID: 2, Name: "Bob", Email: "b@c.com"}
			return db.Users.Insert(tx, user2)
		},

		State: DBState{
			UsersByID: []User{
				{ID: 1, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com"},
			},
			UsersByEmail: []User{
				{ID: 1, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com"},
			},
			UsersByName: []User{
				{ID: 1, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com"},
			},
		},
	}, {

		Name: "Update",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			u := db.Users.ByID.Get(tx, &User{ID: 2})
			if u == nil {
				return errs.NotFound
			}

			u.Email = "a@b.com"
			return db.Users.Update(tx, u)
		},

		ExpectedUpdateError: errs.Duplicate,

		State: DBState{
			UsersByID: []User{
				{ID: 1, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com"},
			},
			UsersByEmail: []User{
				{ID: 1, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com"},
			},
			UsersByName: []User{
				{ID: 1, Name: "Alice", Email: "a@b.com"},
				{ID: 2, Name: "Bob", Email: "b@c.com"},
			},
		},
	}},
}, {

	Name: "Delete read only",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Delete",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			return db.Users.Delete(db.Snapshot(), 1)
		},

		ExpectedUpdateError: errs.ReadOnly,

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Delete not found",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Delete",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			return db.Users.Delete(tx, 2)
		},

		ExpectedUpdateError: errs.NotFound,

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {

	Name: "Index general",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			user := &User{ID: 1, Name: "Alice", Email: "a@b.com"}
			return db.Users.Insert(tx, user)
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Get found",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			expected := &User{ID: 1, Name: "Alice", Email: "a@b.com"}

			u := db.Users.ByID.Get(tx, &User{ID: 1})
			if u == nil {
				return errs.NotFound
			}
			if !reflect.DeepEqual(u, expected) {
				return errors.New("Not equal (id)")
			}

			u = db.Users.ByEmail.Get(tx, &User{Email: "a@b.com"})
			if u == nil {
				return errs.NotFound
			}
			if !reflect.DeepEqual(u, expected) {
				return errors.New("Not equal (email)")
			}

			return nil
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Get not found",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			if u := db.Users.ByID.Get(tx, &User{ID: 2}); u != nil {
				return errors.New("Found (id)")
			}

			if u := db.Users.ByEmail.Get(tx, &User{Email: "x@b.com"}); u != nil {
				return errors.New("Found (email)")
			}

			return nil
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Has (true)",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			if ok := db.Users.ByID.Has(tx, &User{ID: 1}); !ok {
				return errors.New("Not found (id)")
			}

			if ok := db.Users.ByEmail.Has(tx, &User{Email: "a@b.com"}); !ok {
				return errors.New("Not found (email)")
			}

			return nil
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}, {
		Name: "Has (false)",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			if ok := db.Users.ByID.Has(tx, &User{ID: 2}); ok {
				return errors.New("Found (id)")
			}

			if ok := db.Users.ByEmail.Has(tx, &User{Email: "x@b.com"}); ok {
				return errors.New("Found (email)")
			}

			return nil
		},

		State: DBState{
			UsersByID:    []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByEmail: []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
			UsersByName:  []User{{ID: 1, Name: "Alice", Email: "a@b.com"}},
		},
	}},
}, {
	Name: "Mutate while iterating",

	Steps: []DBTestStep{{

		Name: "Insert",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) error {
			for i := 0; i < 4; i++ {
				user := &User{
					ID:    uint64(i) + 1,
					Name:  fmt.Sprintf("User%d", i),
					Email: fmt.Sprintf("user.%d@x.com", i),
				}
				if err := db.Users.Insert(tx, user); err != nil {
					return err
				}
			}
			return nil
		},

		State: DBState{
			UsersByID: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1", Email: "user.1@x.com"},
				{ID: 3, Name: "User2", Email: "user.2@x.com"},
				{ID: 4, Name: "User3", Email: "user.3@x.com"},
			},
			UsersByEmail: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1", Email: "user.1@x.com"},
				{ID: 3, Name: "User2", Email: "user.2@x.com"},
				{ID: 4, Name: "User3", Email: "user.3@x.com"},
			},
			UsersByName: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1", Email: "user.1@x.com"},
				{ID: 3, Name: "User2", Email: "user.2@x.com"},
				{ID: 4, Name: "User3", Email: "user.3@x.com"},
			},
		},
	}, {

		Name: "Modify while iterating",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) (err error) {

			first := true
			pivot := User{Name: "User1"}
			db.Users.ByName.AscendAfter(tx, &pivot, func(u *User) bool {
				u.Name += "Mod"
				if err = db.Users.Update(tx, u); err != nil {
					return false
				}
				if first {
					first = false
					return true
				}

				prev := db.Users.ByID.Get(tx, &User{ID: u.ID - 1})
				if prev == nil {
					err = errors.New("Previous user not found")
					return false
				}

				if !strings.HasSuffix(prev.Name, "Mod") {
					err = errors.New("Incorrect user name: " + prev.Name)
					return false
				}

				return true
			})
			return nil
		},

		State: DBState{
			UsersByID: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1Mod", Email: "user.1@x.com"},
				{ID: 3, Name: "User2Mod", Email: "user.2@x.com"},
				{ID: 4, Name: "User3Mod", Email: "user.3@x.com"},
			},
			UsersByEmail: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1Mod", Email: "user.1@x.com"},
				{ID: 3, Name: "User2Mod", Email: "user.2@x.com"},
				{ID: 4, Name: "User3Mod", Email: "user.3@x.com"},
			},
			UsersByName: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1Mod", Email: "user.1@x.com"},
				{ID: 3, Name: "User2Mod", Email: "user.2@x.com"},
				{ID: 4, Name: "User3Mod", Email: "user.3@x.com"},
			},
		},
	}, {

		Name: "Iterate after modifying",

		Update: func(t *testing.T, db TestDB, tx *Snapshot) (err error) {

			u := &User{ID: 5, Name: "User4Mod", Email: "user.4@x.com"}
			if err := db.Users.Insert(tx, u); err != nil {
				return err
			}

			first := true
			db.Users.ByName.DescendAfter(tx, &User{Name: "User5Mod"}, func(u *User) bool {
				u.Name = strings.TrimSuffix(u.Name, "Mod")
				if err = db.Users.Update(tx, u); err != nil {
					return false
				}
				if first {
					first = false
					return true
				}

				prev := db.Users.ByID.Get(tx, &User{ID: u.ID + 1})
				if prev == nil {
					err = errors.New("Previous user not found")
					return false
				}

				if strings.HasSuffix(prev.Name, "Mod") {
					err = errors.New("Incorrect user name: " + prev.Name)
					return false
				}

				return true
			})
			return nil
		},

		State: DBState{
			UsersByID: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1", Email: "user.1@x.com"},
				{ID: 3, Name: "User2", Email: "user.2@x.com"},
				{ID: 4, Name: "User3", Email: "user.3@x.com"},
				{ID: 5, Name: "User4", Email: "user.4@x.com"},
			},
			UsersByEmail: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1", Email: "user.1@x.com"},
				{ID: 3, Name: "User2", Email: "user.2@x.com"},
				{ID: 4, Name: "User3", Email: "user.3@x.com"},
				{ID: 5, Name: "User4", Email: "user.4@x.com"},
			},
			UsersByName: []User{
				{ID: 1, Name: "User0", Email: "user.0@x.com"},
				{ID: 2, Name: "User1", Email: "user.1@x.com"},
				{ID: 3, Name: "User2", Email: "user.2@x.com"},
				{ID: 4, Name: "User3", Email: "user.3@x.com"},
				{ID: 5, Name: "User4", Email: "user.4@x.com"},
			},
		},
	}},
}}