import { Nullable } from "../types";

/**
 * This class implement a typical dictionary using a string as key and the generic type T as value.
 * The underlying implementation relies on an associative array to ensure the best performances.
 * The value can be anything including 'null' but except 'undefined'
 */
export class StringDictionary<T> {

    /**
     * This will clear this dictionary and copy the content from the 'source' one.
     * If the T value is a custom object, it won't be copied/cloned, the same object will be used
     * @param source the dictionary to take the content from and copy to this dictionary
     */
    public copyFrom(source: StringDictionary<T>) {
        this.clear();
        source.forEach((t, v) => this.add(t, v));
    }

    /**
     * Get a value based from its key
     * @param key the given key to get the matching value from
     * @return the value if found, otherwise undefined is returned
     */
    public get(key: string): T | undefined {
        var val = this._data[key];
        if (val !== undefined) {
            return val;
        }
        return undefined;
    }

    /**
     * Get a value from its key or add it if it doesn't exist.
     * This method will ensure you that a given key/data will be present in the dictionary.
     * @param key the given key to get the matching value from
     * @param factory the factory that will create the value if the key is not present in the dictionary.
     * The factory will only be invoked if there's no data for the given key.
     * @return the value corresponding to the key.
     */
    public getOrAddWithFactory(key: string, factory: (key: string) => T): T {
        var val = this.get(key);
        if (val !== undefined) {
            return val;
        }

        val = factory(key);
        if (val) {
            this.add(key, val);
        }

        return val;
    }

    /**
     * Get a value from its key if present in the dictionary otherwise add it
     * @param key the key to get the value from
     * @param val if there's no such key/value pair in the dictionary add it with this value
     * @return the value corresponding to the key
     */
    public getOrAdd(key: string, val: T): T {
        var curVal = this.get(key);
        if (curVal !== undefined) {
            return curVal;
        }

        this.add(key, val);
        return val;
    }

    /**
     * Check if there's a given key in the dictionary
     * @param key the key to check for
     * @return true if the key is present, false otherwise
     */
    public contains(key: string): boolean {
        return this._data[key] !== undefined;
    }

    /**
     * Add a new key and its corresponding value
     * @param key the key to add
     * @param value the value corresponding to the key
     * @return true if the operation completed successfully, false if we couldn't insert the key/value because there was already this key in the dictionary
     */
    public add(key: string, value: T): boolean {
        if (this._data[key] !== undefined) {
            return false;
        }
        this._data[key] = value;
        ++this._count;
        return true;
    }

    /**
     * Update a specific value associated to a key
     * @param key defines the key to use
     * @param value defines the value to store
     * @returns true if the value was updated (or false if the key was not found)
     */
    public set(key: string, value: T): boolean {
        if (this._data[key] === undefined) {
            return false;
        }
        this._data[key] = value;
        return true;
    }

    /**
     * Get the element of the given key and remove it from the dictionary
     * @param key defines the key to search
     * @returns the value associated with the key or null if not found
     */
    public getAndRemove(key: string): Nullable<T> {
        let val = this.get(key);
        if (val !== undefined) {
            delete this._data[key];
            --this._count;
            return val;
        }
        return null;
    }

    /**
     * Remove a key/value from the dictionary.
     * @param key the key to remove
     * @return true if the item was successfully deleted, false if no item with such key exist in the dictionary
     */
    public remove(key: string): boolean {
        if (this.contains(key)) {
            delete this._data[key];
            --this._count;
            return true;
        }
        return false;
    }

    /**
     * Clear the whole content of the dictionary
     */
    public clear() {
        this._data = {};
        this._count = 0;
    }

    /**
     * Gets the current count
     */
    public get count() {
        return this._count;
    }

    /**
     * Execute a callback on each key/val of the dictionary.
     * Note that you can remove any element in this dictionary in the callback implementation
     * @param callback the callback to execute on a given key/value pair
     */
    public forEach(callback: (key: string, val: T) => void) {
        for (let cur in this._data) {
            var val = this._data[cur];
            callback(cur, val);
        }
    }

    /**
     * Execute a callback on every occurrence of the dictionary until it returns a valid TRes object.
     * If the callback returns null or undefined the method will iterate to the next key/value pair
     * Note that you can remove any element in this dictionary in the callback implementation
     * @param callback the callback to execute, if it return a valid T instanced object the enumeration will stop and the object will be returned
     * @returns the first item
     */
    public first<TRes>(callback: (key: string, val: T) => TRes) {
        for (let cur in this._data) {
            var val = this._data[cur];
            var res = callback(cur, val);
            if (res) {
                return res;
            }
        }
        return null;
    }

    private _count = 0;
    private _data: { [key: string]: T } = {};
}