/**
 *  LogarithmPlotter - 2D plotter software to make BODE plots, sequences and distribution functions.
 *  Copyright (C) 2021-2024  Ad5001
 * 
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 * 
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 * 
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

.pragma library

.import "expr-eval.js" as ExprEval
.import "../../modules.mjs" as M

const evalVariables = {
    // Variables not provided by expr-eval.js, needs to be provided manually
    "pi": Math.PI,
    "PI": Math.PI,
    "π": Math.PI,
    "inf": Infinity,
    "infinity": Infinity,
    "Infinity": Infinity,
    "∞": Infinity,
    "e": Math.E,
    "E": Math.E,
    "true": true,
    "false": false
}

class ExprParserAPI extends M.Module {
    constructor() {
        super('ExprParser', [
            /** @type {ObjectsAPI} */
            Modules.Objects
        ])
        this.currentVars = {}
        this.Internals = ExprEval
        this._parser = new ExprEval.Parser()

        this._parser.consts = Object.assign({}, this._parser.consts, evalVariables)

        this._parser.functions.integral = this.integral.bind(this)
        this._parser.functions.derivative = this.derivative.bind(this)
    }

    /**
     * Parses arguments for a function, returns the corresponding JS function if it exists.
     * Throws either usage error otherwise.
     * @param {array} args - Arguments of the function, either [ ExecutableObject ] or [ string, variable ].
     * @param {string} usage1 - Usage for executable object.
     * @param {string} usage2 - Usage for string function.
     * @return {function} JS function to call.
     */
    parseArgumentsForFunction(args, usage1, usage2) {
        let f, target, variable
        if(args.length === 1) {
            // Parse object
            f = args[0]
            if(typeof f !== 'object' || !f.execute)
                throw EvalError(qsTranslate('usage', 'Usage: %1').arg(usage1))
            let target = f
            f = (x) => target.execute(x)
        } else if(args.length === 2) {
            // Parse variable
            [f,variable] = args
            if(typeof f !== 'string' || typeof variable !== 'string')
                throw EvalError(qsTranslate('usage', 'Usage: %1').arg(usage2))
            f = this._parser.parse(f).toJSFunction(variable, this.currentVars)
        } else
            throw EvalError(qsTranslate('usage', 'Usage: %1 or\n%2').arg(usage1).arg(usage2))
        return f
    }

    /**
     * @param {string} expression - Expression to parse
     */
    parse(expression) {
        return this._parser.parse(expression)
    }

    integral(a, b, ...args) {
        let usage1 = qsTranslate('usage', 'integral(<from: number>, <to: number>, <f: ExecutableObject>)')
        let usage2 = qsTranslate('usage', 'integral(<from: number>, <to: number>, <f: string>, <variable: string>)')
        let f = this.parseArgumentsForFunction(args, usage1, usage2)
        if(a == null || b == null)
            throw EvalError(qsTranslate('usage', 'Usage: %1 or\n%2').arg(usage1).arg(usage2))

        // https://en.wikipedia.org/wiki/Simpson%27s_rule
        // Simpler, faster than tokenizing the expression
        return (b-a)/6*(f(a)+4*f((a+b)/2)+f(b))
    }

    derivative(...args) {
        let usage1 = qsTranslate('usage', 'derivative(<f: ExecutableObject>, <x: number>)')
        let usage2 = qsTranslate('usage', 'derivative(<f: string>, <variable: string>, <x: number>)')
        let x = args.pop()
        let f = this.parseArgumentsForFunction(args, usage1, usage2)
        if(x == null)
            throw EvalError(qsTranslate('usage', 'Usage: %1 or\n%2').arg(usage1).arg(usage2))

        let derivative_precision = x/10
        return (f(x+derivative_precision/2)-f(x-derivative_precision/2))/derivative_precision
    }
}

/** @type {ExprParserAPI} */
Modules.ExprParser = Modules.ExprParser || new ExprParserAPI()