export interface ObservableLike {
	subscribe(observer: (value: any) => void): void;
}

export type Constructor = (new (...args: Array<any>) => any);

/** Specify one or more expectations the thrown error must satisfy. */
export type ThrowsExpectation = {
	/** The thrown error must have a code that equals the given string or number. */
	code?: string | number;

	/** The thrown error must be an instance of this constructor. */
	instanceOf?: Constructor;

	/** The thrown error must be strictly equal to this value. */
	is?: Error;

	/** The thrown error must have a message that equals the given string, or matches the regular expression. */
	message?: string | RegExp;

	/** The thrown error must have a name that equals the given string. */
	name?: string;
};

/** Options that can be passed to the `t.snapshot()` assertion. */
export type SnapshotOptions = {
	/** If provided and not an empty string, used to select the snapshot to compare the `expected` value against. */
	id?: string;
};

export interface Assertions {
	/** Assert that `actual` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to `expected`. */
	deepEqual: DeepEqualAssertion;

	/** Fail the test. */
	fail: FailAssertion;

	/** Assert that `actual` is strictly false. */
	false: FalseAssertion;

	/** Assert that `actual` is [falsy](https://developer.mozilla.org/en-US/docs/Glossary/Falsy). */
	falsy: FalsyAssertion;

	/**
	 * Assert that `actual` is [the same
	 * value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) as `expected`.
	 */
	is: IsAssertion;

	/**
	 * Assert that `actual` is not [the same
	 * value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) as `expected`.
	 */
	not: NotAssertion;

	/** Assert that `actual` is not [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to `expected`. */
	notDeepEqual: NotDeepEqualAssertion;

	/** Assert that `string` does not match the regular expression. */
	notRegex: NotRegexAssertion;

	/** Assert that the function does not throw. */
	notThrows: NotThrowsAssertion;

	/** Assert that the async function does not throw, or that the promise does not reject. Must be awaited. */
	notThrowsAsync: NotThrowsAsyncAssertion;

	/** Count a passing assertion. */
	pass: PassAssertion;

	/** Assert that `string` matches the regular expression. */
	regex: RegexAssertion;

	/**
	 * Assert that `expected` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to a
	 * previously recorded [snapshot](https://github.com/concordancejs/concordance#serialization-details), or if
	 * necessary record a new snapshot.
	 */
	snapshot: SnapshotAssertion;

	/**
	 * Assert that the function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error value.
	 */
	throws: ThrowsAssertion;

	/**
	 * Assert that the async function throws [an error](https://www.npmjs.com/package/is-error), or the promise rejects
	 * with one. If so, returns a promise for the error value, which must be awaited.
	 */
	throwsAsync: ThrowsAsyncAssertion;

	/** Assert that `actual` is strictly true. */
	true: TrueAssertion;

	/** Assert that `actual` is [truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy). */
	truthy: TruthyAssertion;
}

export interface DeepEqualAssertion {
	/** Assert that `actual` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to `expected`. */
	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, expected: any, message?: string): void;
}

export interface FailAssertion {
	/** Fail the test. */
	(message?: string): void;

	/** Skip this assertion. */
	skip(message?: string): void;
}

export interface FalseAssertion {
	/** Assert that `actual` is strictly false. */
	(actual: any, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, message?: string): void;
}

export interface FalsyAssertion {
	/** Assert that `actual` is [falsy](https://developer.mozilla.org/en-US/docs/Glossary/Falsy). */
	(actual: any, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, message?: string): void;
}

export interface IsAssertion {
	/**
	 * Assert that `actual` is [the same
	 * value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) as `expected`.
	 */
	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, expected: any, message?: string): void;
}

export interface NotAssertion {
	/**
	 * Assert that `actual` is not [the same
	 * value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) as `expected`.
	 */
	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, expected: any, message?: string): void;
}

export interface NotDeepEqualAssertion {
	/** Assert that `actual` is not [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to `expected`. */
	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, expected: any, message?: string): void;
}

export interface NotRegexAssertion {
	/** Assert that `string` does not match the regular expression. */
	(string: string, regex: RegExp, message?: string): void;

	/** Skip this assertion. */
	skip(string: string, regex: RegExp, message?: string): void;
}

export interface NotThrowsAssertion {
	/** Assert that the function does not throw. */
	(fn: () => any, message?: string): void;

	/** Skip this assertion. */
	skip(fn: () => any, message?: string): void;
}

export interface NotThrowsAsyncAssertion {
	/** Assert that the async function does not throw. You must await the result. */
	(fn: () => PromiseLike<any>, message?: string): Promise<void>;

	/** Assert that the promise does not reject. You must await the result. */
	(promise: PromiseLike<any>, message?: string): Promise<void>;

	/** Skip this assertion. */
	skip(nonThrower: any, message?: string): void;
}

export interface PassAssertion {
	/** Count a passing assertion. */
	(message?: string): void;

	/** Skip this assertion. */
	skip(message?: string): void;
}

export interface RegexAssertion {
	/** Assert that `string` matches the regular expression. */
	(string: string, regex: RegExp, message?: string): void;

	/** Skip this assertion. */
	skip(string: string, regex: RegExp, message?: string): void;
}

export interface SnapshotAssertion {
	/**
	 * Assert that `expected` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to a
	 * previously recorded [snapshot](https://github.com/concordancejs/concordance#serialization-details), or if
	 * necessary record a new snapshot.
	 */
	(expected: any, message?: string): void;

	/**
	 * Assert that `expected` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to a
	 * previously recorded [snapshot](https://github.com/concordancejs/concordance#serialization-details) (selected
	 * through `options.id` if provided), or if necessary record a new snapshot.
	 */
	(expected: any, options: SnapshotOptions, message?: string): void;

	/** Skip this assertion. */
	skip(expected: any, message?: string): void;

	/** Skip this assertion. */
	skip(expected: any, options: SnapshotOptions, message?: string): void;
}

export interface ThrowsAssertion {
	/**
	 * Assert that the function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error value.
	 */
	<ThrownError extends Error>(fn: () => any, expectations?: null, message?: string): ThrownError;

	/**
	 * Assert that the function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error value.
	 * The error must be an instance of the given constructor.
	 */
	<ThrownError extends Error>(fn: () => any, constructor: Constructor, message?: string): ThrownError;

	/**
	 * Assert that the function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error value.
	 * The error must have a message that matches the regular expression.
	 */
	<ThrownError extends Error>(fn: () => any, regex: RegExp, message?: string): ThrownError;

	/**
	 * Assert that the function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error value.
	 * The error must have a message equal to `errorMessage`.
	 */
	<ThrownError extends Error>(fn: () => any, errorMessage: string, message?: string): ThrownError;

	/**
	 * Assert that the function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error value.
	 * The error must satisfy all expectations.
	 */
	<ThrownError extends Error>(fn: () => any, expectations: ThrowsExpectation, message?: string): ThrownError;

	/** Skip this assertion. */
	skip(fn: () => any, expectations?: any, message?: string): void;
}

export interface ThrowsAsyncAssertion {
	/**
	 * Assert that the async function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error
	 * value. You must await the result.
	 */
	<ThrownError extends Error>(fn: () => PromiseLike<any>, expectations?: null, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the async function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error
	 * value. You must await the result. The error must be an instance of the given constructor.
	 */
	<ThrownError extends Error>(fn: () => PromiseLike<any>, constructor: Constructor, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the async function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error
	 * value. You must await the result. The error must have a message that matches the regular expression.
	 */
	<ThrownError extends Error>(fn: () => PromiseLike<any>, regex: RegExp, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the async function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error
	 * value. You must await the result. The error must have a message equal to `errorMessage`.
	 */
	<ThrownError extends Error>(fn: () => PromiseLike<any>, errorMessage: string, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the async function throws [an error](https://www.npmjs.com/package/is-error). If so, returns the error
	 * value. You must await the result. The error must satisfy all expectations.
	 */
	<ThrownError extends Error>(fn: () => PromiseLike<any>, expectations: ThrowsExpectation, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the promise rejects with [an error](https://www.npmjs.com/package/is-error). If so, returns the
	 * rejection reason. You must await the result.
	 */
	<ThrownError extends Error>(promise: PromiseLike<any>, expectations?: null, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the promise rejects with [an error](https://www.npmjs.com/package/is-error). If so, returns the
	 * rejection reason. You must await the result. The error must be an instance of the given constructor.
	 */
	<ThrownError extends Error>(promise: PromiseLike<any>, constructor: Constructor, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the promise rejects with [an error](https://www.npmjs.com/package/is-error). If so, returns the
	 * rejection reason. You must await the result. The error must have a message that matches the regular expression.
	 */
	<ThrownError extends Error>(promise: PromiseLike<any>, regex: RegExp, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the promise rejects with [an error](https://www.npmjs.com/package/is-error). If so, returns the
	 * rejection reason. You must await the result. The error must have a message equal to `errorMessage`.
	 */
	<ThrownError extends Error>(promise: PromiseLike<any>, errorMessage: string, message?: string): Promise<ThrownError>;

	/**
	 * Assert that the promise rejects with [an error](https://www.npmjs.com/package/is-error). If so, returns the
	 * rejection reason. You must await the result. The error must satisfy all expectations.
	 */
	<ThrownError extends Error>(promise: PromiseLike<any>, expectations: ThrowsExpectation, message?: string): Promise<ThrownError>;

	/** Skip this assertion. */
	skip(thrower: any, expectations?: any, message?: string): void;
}

export interface TrueAssertion {
	/** Assert that `actual` is strictly true. */
	(actual: any, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, message?: string): void;
}

export interface TruthyAssertion {
	/** Assert that `actual` is [truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy). */
	(actual: any, message?: string): void;

	/** Skip this assertion. */
	skip(actual: any, message?: string): void;
}

/** The `t` value passed to test & hook implementations. */
export interface ExecutionContext<Context = {}> extends Assertions {
	/** Test context, shared with hooks. */
	context: Context;

	/** Title of the test or hook. */
	readonly title: string;

	log: LogFn;
	plan: PlanFn;
}

export interface LogFn {
	/** Log one or more values. */
	(...values: Array<any>): void;

	/** Skip logging. */
	skip(...values: Array<any>): void;
}

export interface PlanFn {
	/**
	 * Plan how many assertion there are in the test. The test will fail if the actual assertion count doesn't match the
	 * number of planned assertions. See [assertion planning](https://github.com/avajs/ava#assertion-planning).
	 */
	(count: number): void;

	/** Don't plan assertions. */
	skip(count: number): void;
}

/** The `t` value passed to implementations for tests & hooks declared with the `.cb` modifier. */
export interface CbExecutionContext<Context = {}> extends ExecutionContext<Context> {
	/**
	 * End the test. If `error` is [truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy) the test or hook
	 * will fail.
	 */
	end(error?: any): void;
}

export type ImplementationResult = PromiseLike<void> | ObservableLike | void;
export type Implementation<Context = {}> = (t: ExecutionContext<Context>) => ImplementationResult;
export type CbImplementation<Context = {}> = (t: CbExecutionContext<Context>) => ImplementationResult;

/** A reusable test or hook implementation. */
export interface Macro<Args extends any[], Context = {}> {
	(t: ExecutionContext<Context>, ...args: Args): ImplementationResult;

	/**
	 * Implement this function to generate a test (or hook) title whenever this macro is used. `providedTitle` contains
	 * the title provided when the test or hook was declared. Also receives the remaining test arguments.
	 */
	title?: (providedTitle: string | undefined, ...args: Args) => string;
}

/** Alias for a single macro, or an array of macros. */
export type OneOrMoreMacros<Args extends any[], Context> = Macro<Args, Context> | [Macro<Args, Context>, ...Macro<Args, Context>[]];

/** A reusable test or hook implementation, for tests & hooks declared with the `.cb` modifier. */
export interface CbMacro<Args extends any[], Context = {}> {
	(t: CbExecutionContext<Context>, ...args: Args): ImplementationResult;
	title?: (providedTitle: string | undefined, ...args: Args) => string;
}

/** Alias for a single macro, or an array of macros, used for tests & hooks declared with the `.cb` modifier. */
export type OneOrMoreCbMacros<Args extends any[], Context> = CbMacro<Args, Context> | [CbMacro<Args, Context>, ...CbMacro<Args, Context>[]];

/** Infers the types of the additional arguments the macro implementations should be called with. */
export type InferArgs<OneOrMore> =
	OneOrMore extends Macro<infer Args, any> ? Args :
	OneOrMore extends Macro<infer Args, any>[] ? Args :
	OneOrMore extends CbMacro<infer Args, any> ? Args :
	OneOrMore extends CbMacro<infer Args, any>[] ? Args :
	never;

export type TitleOrMacro<Context> = string | OneOrMoreMacros<any, Context>

export type MacroOrFirstArg<TitleOrMacro, Context> =
	TitleOrMacro extends string ? OneOrMoreMacros<any, Context> :
	TitleOrMacro extends OneOrMoreMacros<any, Context> ? InferArgs<TitleOrMacro>[0] :
	never

export type TitleOrCbMacro<Context> = string | OneOrMoreCbMacros<any, Context>

export type CbMacroOrFirstArg<TitleOrMacro, Context> =
	TitleOrMacro extends string ? OneOrMoreCbMacros<any, Context> :
	TitleOrMacro extends OneOrMoreCbMacros<any, Context> ? InferArgs<TitleOrMacro>[0] :
	never

export type RestArgs<TitleOrMacro, MacroOrFirstArg, Context> =
	MacroOrFirstArg extends OneOrMoreMacros<any, Context> ? InferArgs<MacroOrFirstArg> :
	MacroOrFirstArg extends OneOrMoreCbMacros<any, Context> ? InferArgs<MacroOrFirstArg> :
	TitleOrMacro extends OneOrMoreMacros<any, Context> ? Tail<InferArgs<TitleOrMacro>> :
	TitleOrMacro extends OneOrMoreCbMacros<any, Context> ? Tail<InferArgs<TitleOrMacro>> :
	never

export interface TestInterface<Context = {}> {
	/** Declare a concurrent test. */
	(title: string, implementation: Implementation<Context>): void;

	/** Declare a concurrent test that uses one or more macros. Additional arguments are passed to the macro. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Declare a concurrent test that uses one or more macros. The macro is responsible for generating a unique test title. */
	(macro: OneOrMoreMacros<[], Context>): void

	/** Declare a hook that is run once, after all tests have passed. */
	after: AfterInterface<Context>;

	/** Declare a hook that is run after each passing test. */
	afterEach: AfterInterface<Context>;

	/** Declare a hook that is run once, before all tests. */
	before: BeforeInterface<Context>;

	/** Declare a hook that is run before each test. */
	beforeEach: BeforeInterface<Context>;

	/** Declare a test that must call `t.end()` when it's done. */
	cb: CbInterface<Context>;

	/** Declare a test that is expected to fail. */
	failing: FailingInterface<Context>;

	/** Declare tests and hooks that are run serially. */
	serial: SerialInterface<Context>;

	only: OnlyInterface<Context>;
	skip: SkipInterface<Context>;
	todo: TodoDeclaration;
}

export interface AfterInterface<Context = {}> {
	/** Declare a hook that is run once, after all tests have passed. */
	(implementation: Implementation<Context>): void;

	/** Declare a hook that is run once, after all tests have passed. */
	(title: string, implementation: Implementation<Context>): void;

	/** Declare a hook that is run once, after all tests have passed. Additional arguments are passed to the macro. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Declare a hook that is run once, after all tests have passed. */
	(macro: OneOrMoreMacros<[], Context>): void

	/** Declare a hook that is run once, after all tests are done. */
	always: AlwaysInterface<Context>;

	/** Declare a hook that must call `t.end()` when it's done. */
	cb: HookCbInterface<Context>;

	skip: HookSkipInterface<Context>;
}

export interface AlwaysInterface<Context = {}> {
	/** Declare a hook that is run once, after all tests are done. */
	(implementation: Implementation<Context>): void;

	/** Declare a hook that is run once, after all tests are done. */
	(title: string, implementation: Implementation<Context>): void;

	/** Declare a hook that is run once, after all tests are done. Additional arguments are passed to the macro. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Declare a hook that is run once, after all tests are done. */
	(macro: OneOrMoreMacros<[], Context>): void

	/** Declare a hook that must call `t.end()` when it's done. */
	cb: HookCbInterface<Context>;

	skip: HookSkipInterface<Context>;
}

export interface BeforeInterface<Context = {}> {
	/** Declare a hook that is run once, before all tests. */
	(implementation: Implementation<Context>): void;

	/** Declare a hook that is run once, before all tests. */
	(title: string, implementation: Implementation<Context>): void;

	/** Declare a hook that is run once, before all tests. Additional arguments are passed to the macro. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Declare a hook that is run once, before all tests. */
	(macro: OneOrMoreMacros<[], Context>): void

	/** Declare a hook that must call `t.end()` when it's done. */
	cb: HookCbInterface<Context>;

	skip: HookSkipInterface<Context>;
}

export interface CbInterface<Context = {}> {
	/** Declare a test that must call `t.end()` when it's done. */
	(title: string, implementation: CbImplementation<Context>): void;

	/**
	 * Declare a concurrent test that uses one or more macros. The macros must call `t.end()` when they're done.
	 * Additional arguments are passed to the macro.
	 */
	<ToM extends TitleOrCbMacro<Context>, MoA extends CbMacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a concurrent test that uses one or more macros. The macros must call `t.end()` when they're done.
	 * The macro is responsible for generating a unique test title.
	 */
	(macro: OneOrMoreCbMacros<[], Context>): void

	/** Declare a test that is expected to fail. */
	failing: CbFailingInterface<Context>;

	only: CbOnlyInterface<Context>;
	skip: CbSkipInterface<Context>;
}

export interface CbFailingInterface<Context = {}> {
	/** Declare a test that must call `t.end()` when it's done. The test is expected to fail. */
	(title: string, implementation: CbImplementation<Context>): void;

	/**
	 * Declare a test that uses one or more macros. The macros must call `t.end()` when they're done.
	 * Additional arguments are passed to the macro. The test is expected to fail.
	 */
	<ToM extends TitleOrCbMacro<Context>, MoA extends CbMacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a test that uses one or more macros. The macros must call `t.end()` when they're done.
	 * The test is expected to fail.
	 */
	(macro: OneOrMoreCbMacros<[], Context>): void

	only: CbOnlyInterface<Context>;
	skip: CbSkipInterface<Context>;
}

export interface CbOnlyInterface<Context = {}> {
	/**
	 * Declare a test that must call `t.end()` when it's done. Only this test and others declared with `.only()` are run.
	 */
	(title: string, implementation: CbImplementation<Context>): void;

	/**
	 * Declare a test that uses one or more macros. The macros must call `t.end()` when they're done.
	 * Additional arguments are passed to the macro. Only this test and others declared with `.only()` are run.
	 */
	<ToM extends TitleOrCbMacro<Context>, MoA extends CbMacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a test that uses one or more macros. The macros must call `t.end()` when they're done.
	 * Additional arguments are passed to the macro. Only this test and others declared with `.only()` are run.
	 */
	(macro: OneOrMoreCbMacros<[], Context>): void
}

export interface CbSkipInterface<Context = {}> {
	/** Skip this test. */
	(title: string, implementation: CbImplementation<Context>): void;

	/** Skip this test. */
	<ToM extends TitleOrCbMacro<Context>, MoA extends CbMacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Skip this test. */
	(macro: OneOrMoreCbMacros<[], Context>): void
}

export interface FailingInterface<Context = {}> {
	/** Declare a concurrent test. The test is expected to fail. */
	(title: string, implementation: Implementation<Context>): void;

	/**
	 * Declare a concurrent test that uses one or more macros. Additional arguments are passed to the macro.
	 * The test is expected to fail.
	 */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a concurrent test that uses one or more macros. The macro is responsible for generating a unique test title.
	 * The test is expected to fail.
	 */
	(macro: OneOrMoreMacros<[], Context>): void

	only: OnlyInterface<Context>;
	skip: SkipInterface<Context>;
}

export interface HookCbInterface<Context = {}> {
	/** Declare a hook that must call `t.end()` when it's done. */
	(implementation: CbImplementation<Context>): void;

	/** Declare a hook that must call `t.end()` when it's done. */
	(title: string, implementation: CbImplementation<Context>): void;

	/**
	 * Declare a hook that uses one or more macros. The macros must call `t.end()` when they're done.
	 * Additional arguments are passed to the macro.
	 */
	<ToM extends TitleOrCbMacro<Context>, MoA extends CbMacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a hook that uses one or more macros. The macros must call `t.end()` when they're done.
	 */
	(macro: OneOrMoreCbMacros<[], Context>): void

	skip: HookCbSkipInterface<Context>;
}

export interface HookCbSkipInterface<Context = {}> {
	/** Skip this hook. */
	(implementation: CbImplementation<Context>): void;

	/** Skip this hook. */
	(title: string, implementation: CbImplementation<Context>): void;

	/** Skip this hook. */
	<ToM extends TitleOrCbMacro<Context>, MoA extends CbMacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Skip this hook. */
	(macro: OneOrMoreCbMacros<[], Context>): void
}

export interface HookSkipInterface<Context = {}> {
	/** Skip this hook. */
	(implementation: Implementation<Context>): void;

	/** Skip this hook. */
	(title: string, implementation: Implementation<Context>): void;

	/** Skip this hook. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Skip this hook. */
	(macro: OneOrMoreMacros<[], Context>): void
}

export interface OnlyInterface<Context = {}> {
	/** Declare a test. Only this test and others declared with `.only()` are run. */
	(title: string, implementation: Implementation<Context>): void;

	/**
	 * Declare a test that uses one or more macros. Additional arguments are passed to the macro.
	 * Only this test and others declared with `.only()` are run.
	 */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a test that uses one or more macros. The macro is responsible for generating a unique test title.
	 * Only this test and others declared with `.only()` are run.
	 */
	(macro: OneOrMoreMacros<[], Context>): void
}

export interface SerialInterface<Context = {}> {
	/** Declare a serial test. */
	(title: string, implementation: Implementation<Context>): void;

	/** Declare a serial test that uses one or more macros. Additional arguments are passed to the macro. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/**
	 * Declare a serial test that uses one or more macros. The macro is responsible for generating a unique test title.
	 */
	(macro: OneOrMoreMacros<[], Context>): void

	/** Declare a serial hook that is run once, after all tests have passed. */
	after: AfterInterface<Context>;

	/** Declare a serial hook that is run after each passing test. */
	afterEach: AfterInterface<Context>;

	/** Declare a serial hook that is run once, before all tests. */
	before: BeforeInterface<Context>;

	/** Declare a serial hook that is run before each test. */
	beforeEach: BeforeInterface<Context>;

	/** Declare a serial test that must call `t.end()` when it's done. */
	cb: CbInterface<Context>;

	/** Declare a serial test that is expected to fail. */
	failing: FailingInterface<Context>;

	only: OnlyInterface<Context>;
	skip: SkipInterface<Context>;
	todo: TodoDeclaration;
}

export interface SkipInterface<Context = {}> {
	/** Skip this test. */
	(title: string, implementation: Implementation<Context>): void;

	/** Skip this test. */
	<ToM extends TitleOrMacro<Context>, MoA extends MacroOrFirstArg<ToM, Context>>(titleOrMacro: ToM, macroOrArg: MoA, ...rest: RestArgs<ToM, MoA, Context>): void;

	/** Skip this test. */
	(macro: OneOrMoreMacros<[], Context>): void
}

export interface TodoDeclaration {
	/** Declare a test that should be implemented later. */
	(title: string): void;
}

/** Call to declare a test, or chain to declare hooks or test modifiers */
declare const test: TestInterface;

/** Call to declare a test, or chain to declare hooks or test modifiers */
export default test;

/** Call to declare a hook that is run once, after all tests have passed, or chain to declare modifiers. */
export const after: AfterInterface;

/** Call to declare a hook that is run after each passing test, or chain to declare modifiers. */
export const afterEach: AfterInterface;

/** Call to declare a hook that is run once, before all tests, or chain to declare modifiers. */
export const before: BeforeInterface;

/** Call to declare a hook that is run before each test, or chain to declare modifiers. */
export const beforeEach: BeforeInterface;

/** Call to declare a test that must invoke `t.end()` when it's done, or chain to declare modifiers. */
export const cb: CbInterface;

/** Call to declare a test that is expected to fail, or chain to declare modifiers. */
export const failing: FailingInterface;

/** Call to declare a test that is run exclusively, along with other tests declared with `.only()`. */
export const only: OnlyInterface;

/** Call to declare a serial test, or chain to declare serial hooks or test modifiers. */
export const serial: SerialInterface;

/** Skip this test. */
export const skip: SkipInterface;

/** Declare a test that should be implemented later. */
export const todo: TodoDeclaration;


/*
Tail type from <https://github.com/tycho01/typical/blob/25f11ed92c960aab1ebbf47fd6ead9e0ae51d947/src/array/Tail.ts>.

MIT License

Copyright (c) 2017 Thomas Crockett

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/** Get all but the first element of a tuple. */
export type Tail<T extends any[]> =
	((...args: T) => any) extends ((head: any, ...tail: infer R) => any) ? R : never;