/**
 * @fileoverview The State class used by PCjs machines.
 * @author <a href="mailto:Jeff@pcjs.org">Jeff Parsons</a>
 * @copyright © Jeff Parsons 2012-2017
 *
 * This file is part of PCjs, a computer emulation software project at <http://pcjs.org/>.
 *
 * PCjs 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.
 *
 * PCjs 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 PCjs.  If not,
 * see <http://www.gnu.org/licenses/gpl.html>.
 *
 * You are required to include the above copyright notice in every modified copy of this work
 * and to display that copyright notice when the software starts running; see COPYRIGHT in
 * <http://pcjs.org/modules/shared/lib/defines.js>.
 *
 * Some PCjs files also attempt to load external resource files, such as character-image files,
 * ROM files, and disk image files. Those external resource files are not considered part of PCjs
 * for purposes of the GNU General Public License, and the author does not claim any copyright
 * as to their contents.
 */

"use strict";

if (NODE) {
    var web       = require("./../../shared/lib/weblib");
    var Component = require("./../../shared/lib/component");
    var Messages  = require("./messages");
}

/**
 * State(component, sVersion, sSuffix)
 *
 * State objects are used by components to save/restore their state.
 *
 * During a save operation, components add data to a State object via set(),
 * and then return the resulting data using data().
 *
 * During a restore operation, the Computer component passes the results of each
 * data() call back to the originating component.
 *
 * WARNING: Since State objects are low-level objects that have no UI requirements,
 * they do not inherit from the Component class, so you should only use class methods
 * of Component, such as Component.assert(), or Debugger methods if the Debugger
 * is available.
 *
 * @constructor
 * @param {Component} component
 * @param {string} [sVersion] is used to append a major version number to the key
 * @param {string} [sSuffix] is used to append any additional suffixes to the key
 */
function State(component, sVersion, sSuffix) {
    this.id = component.id;
    this.key = State.key(component, sVersion, sSuffix);
    this.dbg = component.dbg;
    this.unload(component.parms);
}

/**
 * State.key(component, sVersion, sSuffix)
 *
 * This encapsulates the key generation code.
 *
 * @param {Component} component
 * @param {string} [sVersion] is used to append a major version number to the key
 * @param {string} [sSuffix] is used to append any additional suffixes to the key
 * @return {string} key
 */
State.key = function(component, sVersion, sSuffix) {
    var key = component.id;
    if (sVersion) {
        var i = sVersion.indexOf('.');
        if (i > 0) key += ".v" + sVersion.substr(0, i);
    }
    if (sSuffix) {
        key += "." + sSuffix;
    }
    return key;
};

/**
 * State.compress(aSrc)
 *
 * @param {Array.<number>|null} aSrc
 * @return {Array.<number>|null} is either the original array (aSrc), or a smaller array of "count, value" pairs (aComp)
 */
State.compress = function(aSrc) {
    if (aSrc) {
        var iSrc = 0;
        var iComp = 0;
        var aComp = [];
        while (iSrc < aSrc.length) {
            var n = aSrc[iSrc];
            Component.assert(n !== undefined);
            var iCompare = iSrc + 1;
            while (iCompare < aSrc.length && aSrc[iCompare] === n) iCompare++;
            aComp[iComp++] = iCompare - iSrc;
            aComp[iComp++] = n;
            iSrc = iCompare;
        }
        if (aComp.length < aSrc.length) return aComp;
    }
    return aSrc;
};

/**
 * State.decompress(aComp)
 *
 * @param {Array.<number>} aComp
 * @param {number} nLength is expected length of decompressed data
 * @return {Array.<number>}
 */
State.decompress = function(aComp, nLength) {
    var iDst = 0;
    var aDst = new Array(nLength);
    var iComp = 0;
    while (iComp < aComp.length - 1) {
        var c = aComp[iComp++];
        var n = aComp[iComp++];
        while (c--) {
            aDst[iDst++] = n;
        }
    }
    Component.assert(aDst.length == nLength);
    return aDst;
};

/**
 * State.compressEvenOdd(aSrc)
 *
 * This is a very simple variation on compress() that compresses all the EVEN elements of aSrc first,
 * followed by all the ODD elements.  This tends to work better on EGA video memory, because when odd/even
 * addressing is enabled (eg, for text modes), the DWORD values tend to alternate, which is the worst case
 * for compress(), but the best case for compressEvenOdd().
 *
 * One wrinkle we support: if the first element is uninitialized, then we assume the entire array is undefined,
 * and return an empty compressed array.  Conversely, decompressEvenOdd() will take an empty compressed array
 * and return an uninitialized array.
 *
 * @param {Array.<number>|null} aSrc
 * @return {Array.<number>|null} is either the original array (aSrc), or a smaller array of "count, value" pairs (aComp)
 */
State.compressEvenOdd = function(aSrc) {
    if (aSrc) {
        var iComp = 0, aComp = [];
        if (aSrc[0] !== undefined) {
            for (var off = 0; off < 2; off++) {
                var iSrc = off;
                while (iSrc < aSrc.length) {
                    var n = aSrc[iSrc];
                    var iCompare = iSrc + 2;
                    while (iCompare < aSrc.length && aSrc[iCompare] === n) iCompare += 2;
                    aComp[iComp++] = (iCompare - iSrc) >> 1;
                    aComp[iComp++] = n;
                    iSrc = iCompare;
                }
            }
        }
        if (aComp.length < aSrc.length) return aComp;
    }
    return aSrc;
};

/**
 * State.decompressEvenOdd(aComp, nLength)
 *
 * This is the counterpart to compressEvenOdd().  Note that because there's nothing in the compressed sequence
 * that differentiates a compress() sequence from a compressEvenOdd() sequence, you simply have to be consistent:
 * if you used even/odd compression, then you must use even/odd decompression.
 *
 * @param {Array.<number>} aComp
 * @param {number} nLength is expected length of decompressed data
 * @return {Array.<number>}
 */
State.decompressEvenOdd = function(aComp, nLength) {
    var iDst = 0;
    var aDst = new Array(nLength);
    var iComp = 0;
    while (iComp < aComp.length - 1) {
        var c = aComp[iComp++];
        var n = aComp[iComp++];
        while (c--) {
            aDst[iDst] = n;
            iDst += 2;
        }
        /*
         * The output of a "count,value" pair will never exceed the end of the output array, so as soon as we reach it
         * the first time, we know it's time to switch to ODD elements, and as soon as we reach it again, we should be
         * done.
         */
        Component.assert(iDst <= nLength || iComp == aComp.length);
        if (iDst == nLength) iDst = 1;
    }
    Component.assert(aDst.length == nLength);
    return aDst;
};

State.prototype = {
    constructor: State,
    /**
     * set(id, data)
     *
     * @this {State}
     * @param {number|string} id
     * @param {Object|string} data
     */
    set: function(id, data) {
        try {
            this[this.id][id] = data;
        } catch(e) {
            Component.log(e.message);
        }
    },
    /**
     * get(id)
     *
     * @this {State}
     * @param {number|string} id
     * @return {Object|string|null}
     */
    get: function(id) {
        return this[this.id][id] || null;
    },
    /**
     * value()
     *
     * Use this instead of data() if you haven't called parse() yet.
     *
     * @this {State}
     * @return {string}
     */
    value: function() {
        return this[this.id];
    },
    /**
     * data()
     *
     * @this {State}
     * @return {Object}
     */
    data: function() {
        return this[this.id];
    },
    /**
     * load(s)
     *
     * WARNING: Make sure you follow this call with either a call to parse() or unload(),
     * because any stringified data that we've loaded isn't usable until it's been parsed.
     *
     * @this {State}
     * @param {Object|string|null} [s]
     * @return {boolean} true if state exists in localStorage, false if not
     */
    load: function(s) {
        if (s) {
            this[this.id] = s;
            this.fLoaded = true;
            return true;
        }
        if (this.fLoaded) {
            /*
             * This is assumed to be a redundant load().
             */
            return true;
        }
        if (web.hasLocalStorage()) {
            s = web.getLocalStorageItem(this.key);
            if (s) {
                this[this.id] = s;
                this.fLoaded = true;
                if (DEBUG) this.printString("localStorage(" + this.key + "): " + s.length + " bytes loaded");
                return true;
            }
        }
        return false;
    },
    /**
     * parse()
     *
     * This completes the load() operation, by parsing what was loaded, on the assumption there
     * might be some benefit to deferring parsing until we've given the user a chance to confirm.
     * Otherwise, load() could have just as easily done this, too.
     *
     * @this {State}
     * @return {boolean} true if successful, false if error
     */
    parse: function() {
        var fSuccess = true;
        try {
            this[this.id] = JSON.parse(this[this.id]);
        } catch (e) {
            Component.error(e.message || e);
            fSuccess = false;
        }
        return fSuccess;
    },
    /**
     * store()
     *
     * @this {State}
     * @return {boolean} true if successful, false if error
     */
    store: function() {
        var fSuccess = true;
        if (web.hasLocalStorage()) {
            var s = JSON.stringify(this[this.id]);
            if (web.setLocalStorageItem(this.key, s)) {
                if (DEBUG) this.printString("localStorage(" + this.key + "): " + s.length + " bytes stored");
            } else {
                /*
                 * WARNING: Because browsers tend to disable all alerts() during an "unload" operation,
                 * it's unlikely anyone will ever see the "quota" errors that occur at this point.  Need to
                 * think of some way to notify the user that there's a problem, and offer a way of cleaning
                 * up old states.
                 */
                Component.error("Unable to store " + s.length + " bytes in browser local storage");
                fSuccess = false;
            }
        }
        return fSuccess;
    },
    /**
     * toString()
     *
     * We can't know whether this might be called before parse() or after parse(), so we check.
     * If before, then this[this.id] will still be in string form; if after, it will be an Object.
     *
     * @this {State}
     * @return {string} JSON-encoded state
     */
    toString: function() {
        var value = this[this.id];
        return (typeof value == "string"? value : JSON.stringify(value));
    },
    /**
     * unload(parms)
     *
     * This discards any data saved via set() or loaded via load(), creating an empty State object.
     * Note that you have to follow this call with an explicit call to store() if you want to remove
     * the state from localStorage as well.
     *
     * @this {State}
     * @param {Object} [parms]
     */
    unload: function(parms) {
        this[this.id] = {};
        if (parms) this.set("parms", parms);
        this.fLoaded = false;
    },
    /**
     * clear(fAll)
     *
     * This unloads the current state, and then clears ALL localStorage for the current machine,
     * independent of version, to reduce the chance of orphaned states wasting part of our limited allocation.
     *
     * @this {State}
     * @param {boolean} [fAll] true to unconditionally clear ALL localStorage for the current domain
     */
    clear: function(fAll) {
        this.unload();
        var aKeys = web.getLocalStorageKeys();
        for (var i = 0; i < aKeys.length; i++) {
            var sKey = aKeys[i];
            if (sKey && (fAll || sKey.substr(0, this.key.length) == this.key)) {
                web.removeLocalStorageItem(sKey);
                if (DEBUG) this.printString("localStorage(" + sKey + ") removed");
                aKeys.splice(i, 1);
                i = 0;
            }
        }
    },
    /**
     * printString(s)
     *
     * @this {State}
     * @param {string} s is any caller-defined string
     */
    printString: function(s) {
        if (DEBUG && DEBUGGER && this.dbg) {
            if (this.dbg.messageEnabled(Messages.LOG)) {
                this.dbg.message(s);
            }
        }
    }
};

if (NODE) module.exports = State;