const STRING_MAX_LENGTH = 128*1024;

/**
 * Create a copy of any object without non-serializable elements to make result safe for JSON.stringify().
 * Guaranteed to never throw.
 *
 * @param {any}    obj     Any data structure
 * @param {object} options
 * @param {function} options.filter - callback that is called on every object's key with (key,value) and should return
 *        value to use (may return undefined to remove unwanted keys). See nodeFilter and browserFilter.
 * @param {number} options.depth - maximum recursion depth. Elements deeper than that are stringified with util.inspect()
 * @param {number} options.maxSize - roughly maximum allowed size of data after JSON serialisation (but it's not guaranteed
 *        that it won't exceed the limit)
 *
 * @see https://github.com/ftlabs/js-abbreviate
 */
function abbreviate(obj, options) {
    if (!options) options = {};

    var filter = options.filter || function(k,v){return v;};
    var maxDepth = options.depth || 10;
    var maxSize = options.maxSize || 1*1024*1024;

    return abbreviateRecursive(undefined, obj, filter, {sizeLeft: maxSize}, maxDepth);
}

function limitStringLength(str) {
    if (str.length > STRING_MAX_LENGTH) {
        return str.substring(0, STRING_MAX_LENGTH/2) + ' … ' + str.substring(str.length - STRING_MAX_LENGTH/2);
    }
    return str;
}

function abbreviateRecursive(key, obj, filter, state, maxDepth) {
    if (state.sizeLeft < 0) {
        return '**skipped**';
    }

    state.sizeLeft -= 5; // rough approximation of JSON overhead

    obj = filter(key, obj);

    try {
        switch(typeof obj) {
            case 'object':
                if (null === obj) {
                    return null;
                }

                if (maxDepth < 0) {
                    break; // fall back to stringification
                }

                var newobj = Array.isArray(obj) ? [] : {};
                for(var i in obj) {
                    newobj[i] = abbreviateRecursive(i, obj[i], filter, state, maxDepth-1);
                    if (state.sizeLeft < 0) break;
                }
                return newobj;

            case 'string':
                obj = limitStringLength(obj);
                state.sizeLeft -= obj.length;
                return obj;

            case 'number':
            case 'boolean':
            case 'undefined':
                return obj;
        }
    } catch(e) {/* fall back to inspect*/}

    try {
        obj = limitStringLength('' + obj);
        state.sizeLeft -= obj.length;
        return obj;
    } catch(e) {
        return "**non-serializable**";
    }
}

function commonFilter(key, val) {
    if ('function' === typeof val) {
        return undefined;
    }

    if (val instanceof Date) {
        return "**Date** " + val;
    }

    if (val instanceof Error) {
        var err = {
            // These properties are implemented as magical getters and don't show up in for in
            stack: val.stack,
            message: val.message,
            name: val.name,
        };
        for(var i in val) {
            err[i] = val[i];
        }
        return err;
    }

    return val;
}

function nodeFilter(key, val) {

    // domain objects are huge and have circular references
    if (key === 'domain' && 'object' === typeof val && val._events) {
        return "**domain ignored**";
    }
    if (key === 'domainEmitter') {
        return "**domainEmitter ignored**";
    }

    if (val === global) {
        return "**global**";
    }

    return commonFilter(key, val);
}

function browserFilter(key, val) {
    if (val === window) {
        return "**window**";
    }

    if (val === document) {
        return "**document**";
    }

    if (val instanceof HTMLElement) {
        var outerHTML = val.outerHTML;
        if ('undefined' != typeof outerHTML) {
            return "**HTMLElement** " + outerHTML;
        }
    }

    return commonFilter(key, val);
}


export {
    abbreviate,
    nodeFilter,
    browserFilter
};

export default function(obj) {
    return abbreviate(obj, {
        filter: browserFilter
    })
};