// written to React"s immutability helpers spec
// see https://facebook.github.io/react/docs/update.html

///<reference path="../typings/index.d.ts"/>
///<reference path="./assign.ts"/>
///<reference path="./verify.ts"/>

namespace Updraft {
	export namespace Delta {
		export interface setter<T> {
			$set: T;
		}
		
		export interface increment {
			$inc: number;
		}
		
		export interface push<T> {
			$push: Array<T>;
		}
		
		export interface unshift<T> {
			$unshift: Array<T>;
		}
		
		export interface splice<T> {
			// array.splice(start, deleteCount[, item1[, item2[, ...]]])
			$splice: Array<Array<number | T>>;
		}
		
		export interface merge<T> {
			$merge: T;
		}
		
		export interface add<T> {
			$add: Array<T>;
		}
		
		export interface deleter<T> {
			$delete: Array<T>;
		}
		
		export type primitive<T> =
			setter<T>;
		
		export type none = void;
		export type bool = primitive<boolean>;
		export type num = primitive<number> | increment;
		export type str = primitive<string>;
		export type date = setter<Date>;
		export type obj = primitive<Object> | merge<Object> | deleter<string>;
		export type enm<T> = primitive<T>;
		
		export type array<T> =
			setter<Array<T>> |
			push<T> |
			unshift<T> |
			splice<T> |
			merge<T>;
		
		export type strArray = array<string>;
		export type numArray = array<number>;
		export type objArray = array<Object>;
		
		export type set<T> =
			setter<Set<T>> |
			add<T> |
			deleter<T>;
		
		export type strSet = set<string>;
	}
	
	export function shallowCopy<T>(x: T): T {
		/* istanbul ignore else: not sure about this one */
		if (Array.isArray(x)) {
			return (<any>x).concat();
		}
		else if (x instanceof Set) {
			return <any>new Set<T>(<any>x);
		}
		else if (typeof x === "object") {
			return assign(new (<any>x).constructor(), x);
		}
		else {
			/* istanbul ignore next: correct AFAIK but unreachable */
			return x;
		}
	}
	
	export function shallowEqual<T>(a: T, b: T): boolean {
		if (Array.isArray(a) && Array.isArray(b)) {
			let aa: any[] = <any>a;
			let bb: any[] = <any>b;
			if (aa.length == bb.length) {
				for (let i = 0; i < aa.length; i++) {
					if (aa[i] != bb[i]) {
						return false;
					}
				}
				return true;
			}
			return false;
		}
		else if (a instanceof Set && b instanceof Set) {
			let aa: Set<any> = <any>a;
			let bb: Set<any> = <any>b;
			if (aa.size == bb.size) {
				let equal = true;
				aa.forEach((elt) => {
					if (equal && !bb.has(elt)) {
						equal = false;
					}
				});
				return equal;
			}
			return false;
		}
		else if (a instanceof Date && b instanceof Date) {
			return (<Date><any>a).getTime() == (<Date><any>b).getTime();
		}
		else if (a && typeof a == "object" && b && typeof b == "object") {
			let akeys = Object.keys(a);
			let bkeys = Object.keys(b);
			if (akeys.length == bkeys.length) {
				for (let key of akeys) {
					if (!(key in b) || a[key] != b[key]) {
						return false;
					}
				}
				return true;
			}
			return false;
		}
		return a == b;
	}
	
	
	export let hasOwnProperty = {}.hasOwnProperty;
	export function keyOf(obj: Object) { return Object.keys(obj)[0]; }
	
	let command = {
		set: keyOf({$set: null}),
		increment: keyOf({$inc: null}),
		push: keyOf({$push: null}),
		unshift: keyOf({$unshift: null}),
		splice: keyOf({$splice: null}),
		merge: keyOf({$merge: null}),
		add: keyOf({$add: null}),
		deleter: keyOf({$delete: null}),
	};
	
	
	function verifyArrayCase(value: any, spec: any, c: string) {
		verify(
			Array.isArray(value),
			"update(): expected target of %s to be an array; got %s.",
			c,
			value
		);
		let specValue = spec[c];
		verify(
			Array.isArray(specValue),
			"update(): expected spec of %s to be an array; got %s. " +
			"Did you forget to wrap your parameter in an array?",
			c,
			specValue
		);
	}
	
	function verifySetCase(value: any, spec: any, c: string) {
		verify(
			value instanceof Set,
			"update(): expected target of %s to be a set; got %s.",
			c,
			value
		);
		let specValue = spec[c];
		verify(
			Array.isArray(specValue),
			"update(): expected spec of %s to be an array; got %s. " +
			"Did you forget to wrap your parameter in an array?",
			c,
			specValue
		);
	}
	
	export function update<Element, Delta>(value: Element, spec: Delta): Element {
		verify(
			typeof spec === "object",
			"update(): You provided a key path to update() that did not contain one " +
			"of %s. Did you forget to include {%s: ...}?",
			Object.keys(command).join(", "),
			command.set
		);

		// verify(
		// 	Object.keys(spec).reduce( function(previousValue: boolean, currentValue: string): boolean {
		// 		return previousValue && (keyOf(spec[currentValue]) in command);
		// 	}, true),
		// 	"update(): argument has an unknown key; supported keys are (%s).  delta: %s",
		// 	Object.keys(command).join(", "),
		// 	spec
		// );
	
		if (hasOwnProperty.call(spec, command.set)) {
			verify(
				Object.keys(spec).length === 1,
				"Cannot have more than one key in an object with %s",
				command.set
			);
	
			return shallowEqual(value, spec[command.set]) ? value : spec[command.set];
		}
	
		if (hasOwnProperty.call(spec, command.increment)) {
			verify(
				typeof(value) === "number" && typeof(spec[command.increment]) === "number",
				"Source (%s) and argument (%s) to %s must be numbers",
				value,
				spec[command.increment],
				command.increment
			);
	
			return value + spec[command.increment];
		}
	
		let changed = false;
	
		if (hasOwnProperty.call(spec, command.merge)) {
			let mergeObj = spec[command.merge];
			let nextValue = <any>shallowCopy(value);
			verify(
				mergeObj && typeof mergeObj === "object",
				"update(): %s expects a spec of type 'object'; got %s",
				command.merge,
				mergeObj
			);
			verify(
				nextValue && typeof nextValue === "object",
				"update(): %s expects a target of type 'object'; got %s",
				command.merge,
				nextValue
			);
			assign(nextValue, spec[command.merge]);
			return shallowEqual(value, nextValue) ? value : nextValue;
		}
	
		if (hasOwnProperty.call(spec, command.deleter) && (typeof value === "object") && !(value instanceof Set)) {
			let keys = <any[]>spec[command.deleter];
			verify(
				keys && Array.isArray(keys),
				"update(): %s expects a spec of type 'array'; got %s",
				command.deleter,
				keys
			);
			let nextValue = <any>shallowCopy(value);
			changed = false;
			keys.forEach((key: string) => {
				if (key in value) {
					delete nextValue[key];
					changed = true;
				}
			});
			return changed ? <any>nextValue : value;
		}
	
		if (hasOwnProperty.call(spec, command.push)) {
			let nextValue: any[] = <any>shallowCopy(value) || [];
			verifyArrayCase(nextValue, spec, command.push);
			if (spec[command.push].length) {
				nextValue.push.apply(nextValue, spec[command.push]);
				return <any>nextValue;
			}
			else {
				return value;
			}
		}
	
		if (hasOwnProperty.call(spec, command.unshift)) {
			verifyArrayCase(value, spec, command.unshift);
			if (spec[command.unshift].length) {
				let nextValue: any[] = <any>shallowCopy(value);
				nextValue.unshift.apply(nextValue, spec[command.unshift]);
				return <any>nextValue;
			}
			else {
				return value;
			}
		}
	
		if (hasOwnProperty.call(spec, command.splice)) {
			let nextValue: any = <any>shallowCopy(value);
			verify(
				Array.isArray(value),
				"Expected %s target to be an array; got %s",
				command.splice,
				value
			);
			verify(
				Array.isArray(spec[command.splice]),
				"update(): expected spec of %s to be an array of arrays; got %s. " +
				"Did you forget to wrap your parameters in an array?",
				command.splice,
				spec[command.splice]
			);
			spec[command.splice].forEach(function(args: any) {
				verify(
					Array.isArray(args),
					"update(): expected spec of %s to be an array of arrays; got %s. " +
					"Did you forget to wrap your parameters in an array?",
					command.splice,
					spec[command.splice]
				);
				(<any>nextValue).splice.apply(nextValue, args);
			});
			return shallowEqual(nextValue, value) ? value : nextValue;
		}
	
		if (hasOwnProperty.call(spec, command.add)) {
			let nextValue: Set<any> = <any>shallowCopy(value) || new Set<any>();
			verifySetCase(nextValue, spec, command.add);
			spec[command.add].forEach(function(item: any) {
				if (!nextValue.has(item)) {
					nextValue.add(item);
					changed = true;
				}
			});
			return changed ? <any>nextValue : value;
		}
	
		if (hasOwnProperty.call(spec, command.deleter) && (value instanceof Set)) {
			let nextValue: Set<any> = <any>shallowCopy(value);
			verifySetCase(value, spec, command.deleter);
			spec[command.deleter].forEach(function(item: any) {
				if (nextValue.delete(item)) {
					changed = true;
				}
			});
			return changed ? <any>nextValue : value;
		}
	
		let nextValue: any;
		for (let k in spec) {
			if (typeof value === "object" && !(command.hasOwnProperty(k))) {
				let oldValue = value[k];
				let newValue = update(oldValue, spec[k]);
				if (oldValue !== newValue) {
					if (!nextValue) {
						nextValue = <any>shallowCopy(value);
					}
					nextValue[k] = newValue;
					changed = true;
				}
			}
		}
	
		return changed ? nextValue : value;
	}
}