import Expression, { Context } from "./Expression";
import Grammar from "./Grammar";

type TransformFunction = (value: any, ...args: any[]) => any;

type BinaryOpFunction = (left: any, right: any) => any;

type UnaryOpFunction = (right: any) => any;

type FunctionFunction = (value: any, ...args: any[]) => any;

/**
 * Jexl is the Javascript Expression Language, capable of parsing and
 * evaluating basic to complex expression strings, combined with advanced
 * xpath-like drilldown into native Javascript objects.
 */
declare class Jexl {
    /**
     * Adds a binary operator to Jexl at the specified precedence. The higher the
     * precedence, the earlier the operator is applied in the order of operations.
     * For example, * has a higher precedence than +, because multiplication comes
     * before division.
     *
     * Please see grammar.js for a listing of all default operators and their
     * precedence values in order to choose the appropriate precedence for the
     * new operator.
     * @param operator The operator string to be added
     * @param precedence The operator's precedence
     * @param fn A function to run to calculate the result. The function
     *      will be called with two arguments: left and right, denoting the values
     *      on either side of the operator. It should return either the resulting
     *      value, or a Promise that resolves with the resulting value.
     */
    addBinaryOp(operator: string, precedence: number, fn: BinaryOpFunction): void;

    /**
     * Adds a unary operator to Jexl. Unary operators are currently only supported
     * on the left side of the value on which it will operate.
     * @param operator The operator string to be added
     * @param fn A function to run to calculate the result. The function
     *      will be called with one argument: the literal value to the right of the
     *      operator. It should return either the resulting value, or a Promise
     *      that resolves with the resulting value.
     */
    addUnaryOp(operator: string, fn: UnaryOpFunction): void;

    /**
     * Adds or replaces a transform function in this Jexl instance.
     * @param name The name of the transform function, as it will be used
     *      within Jexl expressions
     * @param fn The function to be executed when this transform is
     *      invoked. It will be provided with at least one argument:
     *          - {*} value: The value to be transformed
     *          - {...*} args: The arguments for this transform
     */
    addTransform(name: string, fn: TransformFunction): void;

    /**
     * Syntactic sugar for calling {@link #addTransform} repeatedly.  This function
     * accepts a map of one or more transform names to their transform function.
     * @param map A map of transform names to transform functions
     */
    addTransforms(map: { [key: string]: TransformFunction }): void;

    /**
     * Retrieves a previously set transform function.
     * @param name The name of the transform function
     * @returns The transform function
     */
    getTransform(name: string): TransformFunction;

    /**
     * Adds or replaces an expression function in this Jexl instance.
     * @param name The name of the expression function, as it will be
     *      used within Jexl expressions.
     * @param fn The javascript function to be executed when this
     *      expression function is invoked. It will be provided with each argument
     *      supplied in the expression, in the same order.
     */
    addFunction(name: string, fn: FunctionFunction): void;

    /**
     * Syntactic sugar for calling {@link #addFunction} repeatedly. This function
     * accepts a map of one or more expression function names to their javascript
     * function counterpart.
     * @param map A map of expression function names to javascript functions.
     */
    addFunctions(map: { [key: string]: FunctionFunction }): void;

    /**
     * Retrieves a previously set expression function.
     * @param name The name of the expression function
     * @returns The expression function
     */
    getFunction(name: string): FunctionFunction;

    /**
     * Asynchronously evaluates a Jexl string within an optional context.
     * @param expression The Jexl expression to be evaluated
     * @param context A mapping of variables to values, which will be
     *      made accessible to the Jexl expression when evaluating it
     * @returns resolves with the result of the evaluation.
     */
    eval(expression: string, context?: Context): Promise<any>;

    /**
     * Synchronously evaluates a Jexl string within an optional context.
     * @param expression The Jexl expression to be evaluated
     * @param context A mapping of variables to values, which will be
     *      made accessible to the Jexl expression when evaluating it
     * @returns the result of the evaluation.
     * @throws on error
     */
    evalSync(expression: string, context?: Context): any;

    /**
     * Creates an Expression object from the given Jexl expression string, and
     * immediately compiles it. The returned Expression object can then be
     * evaluated multiple times with new contexts, without generating any
     * additional string processing overhead.
     * @param expression The Jexl expression to be compiled
     * @returns The compiled Expression object
     */
    compile(expression: string): Expression;

    /**
     * Constructs an Expression object from a Jexl expression string.
     * @param expression The Jexl expression to be wrapped in an
     *    Expression object
     * @returns The Expression object representing the given string
     */
    createExpression(expression: string): Expression;

    /**
     * Removes a binary or unary operator from the Jexl grammar.
     * @param operator The operator string to be removed
     */
    removeOp(operator: string): void;

    /**
     * The grammar used to compile the expression.
     */
    _grammar: Grammar;
}

/**
 * Jexl is the Javascript Expression Language, capable of parsing and
 * evaluating basic to complex expression strings, combined with advanced
 * xpath-like drill down into native Javascript objects.
 */
declare class BuildableJexl extends Jexl {
    Jexl: { new(): Jexl };
}

declare const exportJexl: BuildableJexl;

export = exportJexl;