A Swift DSL for building SQLite table creation statements intended for GRDB

GRDB Create SQL Builder.swift

struct _CreateTableBuilder {}
struct _PrimaryKeyBuilder {}
struct _ForeignKeyBuilder {}
struct _SQLExpressible {}
struct _SQLSelectable {}
struct _CreateTableSelectBuilder {}

struct SQLColumn {
    var name: String

    init(name: String) {
        self.name = name
    }
}

enum SQL {
    static func create(
        table: String,
        temp: Bool = false,
        ifNotExists: Bool = false,
        withoutRowID: Bool = false) -> _CreateTableBuilder {
        return _CreateTableBuilder()
    }

    static func primaryKey(
        autoIncrement: Bool? = nil,
        order: _Order? = nil,
        onConflict: _ConflictResolution? = nil) -> _PrimaryKeyBuilder {
        return _PrimaryKeyBuilder()
    }

    static func foreignKey(
        table: String,
        columns: SQLColumn...,
        onDelete: _DeleteUpdateAction? = nil,
        onUpdate: _DeleteUpdateAction? = nil,
        deferrable: Bool? = nil) -> _ForeignKeyBuilder {
        return _ForeignKeyBuilder()
    }
}

extension _CreateTableBuilder {
    func column(
        name: SQLColumn,
        primaryKey: _PrimaryKeyBuilder = false,
        affinity: _Affinity = .numeric,
        notNull: _ConflictClause = false,
        unique: _ConflictClause = false,
        check: _SQLExpressible? = nil,
        default: _DefaultOption? = nil,
        collate: String? = nil,
        references: _ForeignKeyBuilder? = nil) -> _CreateTableBuilder {
        return _CreateTableBuilder()
    }

    func foreignKey(
        columns: SQLColumn...,
        onConflict: _ConflictResolution = .abort,
        references: _ForeignKeyBuilder) -> _CreateTableBuilder {
        return _CreateTableBuilder()
    }

    func primaryKey(
        columns: SQLColumn...,
        onConflict: _ConflictResolution = .abort) -> _CreateTableBuilder {
        return _CreateTableBuilder()
    }

    func unique(
        columns: SQLColumn...,
        onConflict: _ConflictResolution = .abort) -> _CreateTableBuilder {
        return _CreateTableBuilder()
    }

    func check(_ expr: _SQLExpressible) -> _CreateTableBuilder {
        return _CreateTableBuilder()
    }

    func select(_ expr: _SQLSelectable) -> _CreateTableSelectBuilder {
        return _CreateTableSelectBuilder()
    }
}

enum _DefaultOption {
    case number(Int)
    case literal(String)
    case expression(_SQLExpressible)
}

enum _DeleteUpdateAction {
    case none
    case restrict
    case setNull
    case setDefault
    case cascade
}

enum _ConflictResolution {
    case rollback
    case abort
    case fail
    case ignore
    case replace
}

enum _Order {
    case asc
    case desc
}

enum _ConflictClause {
    case onConflict(_ConflictResolution)
    case none
}

enum _Affinity {
    case integer
    case text
    case double
    case blob
    case numeric
}

protocol _ConflictResolvable {
    var resolution: _ConflictClause { get }
}

extension _ConflictClause: BooleanLiteralConvertible {
    init(booleanLiteral value: Bool) {
        self = value
            ? .onConflict(.abort)
            : .none
    }
}

extension _ConflictClause: _ConflictResolvable {
    var resolution: _ConflictClause {
        return self
    }
}

extension _PrimaryKeyBuilder: BooleanLiteralConvertible {
    init(booleanLiteral value: Bool) {
        self = value
            ? _PrimaryKeyBuilder()
            : _PrimaryKeyBuilder()
    }
}

extension _DefaultOption: IntegerLiteralConvertible {
    init(integerLiteral value: Int) {
        self = .number(value)
    }
}

extension SQLColumn: StringLiteralConvertible {
    init(unicodeScalarLiteral value: String) {
        self = SQLColumn(name: value)
    }

    init(extendedGraphemeClusterLiteral value: String) {
        self = SQLColumn(name: value)
    }

    init(stringLiteral value: String) {
        self = SQLColumn(name: value)
    }
}

extension _DefaultOption: StringLiteralConvertible {
    init(unicodeScalarLiteral value: String) {
        self = .literal(value)
    }

    init(extendedGraphemeClusterLiteral value: String) {
        self = .literal(value)
    }

    init(stringLiteral value: String) {
        self = .literal(value)
    }
}

SQL.create(table: "foo", ifNotExists: true)
    .column(
        name: "id",
        primaryKey: true,
        affinity: .integer,
        notNull: true)

SQL.create(table: "foo", ifNotExists: true)
    .column(
        name: "id",
        primaryKey: SQL.primaryKey(autoIncrement: true),
        affinity: .integer,
        notNull: true)

SQL.create(table: "foo", ifNotExists: true)
    .column(
        name: "id",
        primaryKey: SQL.primaryKey(
            autoIncrement: true,
            order: .desc,
            onConflict: .abort),
        affinity: .integer,
        notNull: true)

SQL.create(table: "foo", ifNotExists: true)
    .column(
        name: "id",
        primaryKey: SQL.primaryKey(onConflict: .abort),
        affinity: .integer,
        notNull: true)

SQL.create(table: "foo", ifNotExists: true)
    .column(
        name: "bar_id",
        affinity: .integer,
        references: SQL.foreignKey(
            table: "bar",
            columns: "id"))

SQL.create(table: "foo", ifNotExists: true)
    .column(
        name: "bar_id",
        affinity: .integer,
        references: SQL.foreignKey(
            table: "bar",
            columns: "id",
            onDelete: .cascade,
            onUpdate: .cascade,
            deferrable: true))

let fooId: SQLColumn = "foo_id"
let bazId: SQLColumn = "baz_id"
let a: SQLColumn = "a"
let b: SQLColumn = "b"
let c: SQLColumn = "c"

SQL.create(table: "bar", ifNotExists: true)
    .column(name: fooId, affinity: .integer)
    .column(name: bazId, affinity: .integer)
    .column(name: a, affinity: .integer)
    .column(name: b, affinity: .integer)
    .column(name: c, affinity: .integer)
    .unique(columns: fooId, bazId, onConflict: .rollback)
    .primaryKey(columns: a, b, c, onConflict: .rollback) // runtime error if multiple `primaryKey()` used
    .foreignKey(
        columns: fooId,
        onConflict: .rollback,
        references: SQL.foreignKey(
            table: "foo",
            columns: "id"))
    .foreignKey(
        columns: bazId,
        onConflict: .rollback,
        references: SQL.foreignKey(
            table: "baz",
            columns: "id"))

SQL.create(table: "foo", ifNotExists: true)
    .column(name: "id", affinity: .integer)
    .column(name: "a", default: 1)