var _ = require('lodash'),
    Cursor = require('../cursor'),
    VariableScope = require('postman-collection').VariableScope,

    prepareLookupHash,
    extractSNR,
    getIterationData;

/**
 * Returns a hash of IDs and Names of items in an array
 *
 * @param {Array} items
 * @returns {Object}
 */
prepareLookupHash = function (items) {
    var hash = {
        ids: {},
        names: {},
        obj: {}
    };

    _.forEach(items, function (item, index) {
        if (item) {
            item.id && (hash.ids[item.id] = index);
            item.name && (hash.names[item.name] = index);
        }
    });

    return hash;
};

extractSNR = function (executions, previous) {
    var snr = previous || {};

    _.isArray(executions) && executions.forEach(function (execution) {
        _.has(_.get(execution, 'result.return'), 'nextRequest') && (
            (snr.defined = true),
            (snr.value = execution.result.return.nextRequest)
        );
    });

    return snr;
};

/**
 * Returns the data for the given iteration
 *
 * @function getIterationData
 * @param {Array} data - The data array containing all iterations' data
 * @param {Number} iteration - The iteration to get data for
 * @return {Any} - The data for the iteration
 */
getIterationData = function (data, iteration) {
    // if iteration has a corresponding data element use that
    if (iteration < data.length) {
        return data[iteration];
    }

    // otherwise use the last data element
    return data[data.length - 1];
};

/**
 * Adds options
 * disableSNR:Boolean
 *
 * @type {Object}
 */
module.exports = {
    init: function (done) {
        var state = this.state;

        // ensure that the environment, globals and collectionVariables are in VariableScope instance format
        state.environment = VariableScope.isVariableScope(state.environment) ? state.environment :
            new VariableScope(state.environment);
        state.globals = VariableScope.isVariableScope(state.globals) ? state.globals :
            new VariableScope(state.globals);
        state.collectionVariables = VariableScope.isVariableScope(state.collectionVariables) ?
            state.collectionVariables : new VariableScope(state.collectionVariables);
        state._variables = new VariableScope();

        // ensure that the items and iteration data set is in place
        !_.isArray(state.items) && (state.items = []);
        !_.isArray(state.data) && (state.data = []);
        !_.isObject(state.data[0]) && (state.data[0] = {});

        // if the location in state is already normalised then go ahead and queue iteration, else normalise the
        // location
        state.cursor = Cursor.box(state.cursor, { // we pass bounds to ensure there is no stale state
            cycles: this.options.iterationCount,
            length: state.items.length
        });
        this.waterfall = state.cursor; // copy the location object to instance for quick access

        // queue the iteration command on start
        this.queue('waterfall', {
            coords: this.waterfall.current(),
            static: true,
            start: true
        });

        // clear the variable that is supposed to store item name and id lookup hash for easy setNextRequest
        this.snrHash = null; // we populate it in the first SNR call

        done();
    },

    triggers: ['beforeIteration', 'iteration'],

    process: {
        /**
         * This processor simply queues scripts and requests in a linear chain.
         *
         * @param {Object} payload
         * @param {Object} payload.coords
         * @param {Boolean} [payload.static=false]
         * @param {Function} next
         */
        waterfall: function (payload, next) {
            // we procure the coordinates that we have to pick item and data from. the data is
            var coords = payload.static ? payload.coords : this.waterfall.whatnext(payload.coords),
                item = this.state.items[coords.position],
                delay;

            // if there is nothing to process, we bail out from here, even before we enter the iteration cycle
            if (coords.empty) {
                return next();
            }

            if (payload.stopRunNow) {
                this.triggers.iteration(null, payload.coords);

                return next();
            }

            // if it is a beginning of a run, we need to raise events for iteration start
            if (payload.start) {
                this.triggers.beforeIteration(null, coords);
            }

            // if this is a new iteration, we close the previous one and start new
            if (coords.cr) {
                // getting the iteration delay here ensures that delay is only called between two iterations
                delay = _.get(this.options, 'delay.iteration', 0);

                this.triggers.iteration(null, payload.coords);
                this.triggers.beforeIteration(null, coords);
            }

            // if this is end of waterfall, it is an end of iteration and also end of run
            if (coords.eof) {
                this.triggers.iteration(null, coords);

                return next();
            }

            this.queueDelay(function () {
                this.queue('item', {
                    item: item,
                    coords: coords,
                    data: getIterationData(this.state.data, coords.iteration),
                    environment: this.state.environment,
                    globals: this.state.globals,
                    collectionVariables: this.state.collectionVariables,
                    _variables: this.state._variables
                }, function (executionError, executions) {
                    var snr = {},
                        nextCoords,
                        seekingToStart,
                        stopRunNow,

                        stopOnFailure = this.options.stopOnFailure;

                    if (!executionError) {
                        // extract set next request
                        snr = extractSNR(executions.prerequest);
                        snr = extractSNR(executions.test, snr);
                    }

                    if (!this.options.disableSNR && snr.defined) {
                        // prepare the snr lookup hash if it is not already provided
                        // @todo - figure out a way to reset this post run complete
                        !this.snrHash && (this.snrHash = prepareLookupHash(this.state.items));

                        // if it is null, we do not proceed further and move on
                        // see if a request is found in the hash and then reset the coords position to the lookup
                        // value.
                        (snr.value !== null) && (snr.position = // eslint-disable-next-line no-nested-ternary
                            this.snrHash[_.has(this.snrHash.ids, snr.value) ? 'ids' :
                                (_.has(this.snrHash.names, snr.value) ? 'names' : 'obj')][snr.value]);

                        snr.valid = _.isNumber(snr.position);
                    }

                    nextCoords = _.clone(coords);

                    if (snr.valid) {
                        // if the position was detected, we set the position to the one previous to the desired location
                        // this ensures that the next call to .whatnext() will return the desired position.
                        nextCoords.position = snr.position - 1;
                    }
                    else {
                        // if snr was requested, but not valid, we stop this iteration.
                        // stopping an iteration is equivalent to seeking the last position of the current
                        // iteration, so that the next call to .whatnext() will automatically move to the next
                        // iteration.
                        (snr.defined || executionError) && (nextCoords.position = nextCoords.length - 1);

                        // If we need to stop on a run, we set the stop flag to true.
                        (stopOnFailure && executionError) && (stopRunNow = true);
                    }

                    // @todo - do this in unhacky way
                    if (nextCoords.position === -1) {
                        nextCoords.position = 0;
                        seekingToStart = true;
                    }

                    this.waterfall.seek(nextCoords.position, nextCoords.iteration, function (err, chngd, coords) {
                        // this condition should never arise, so better throw error when this happens
                        if (err) {
                            throw err;
                        }

                        this.queue('waterfall', {
                            coords: coords,
                            static: seekingToStart,
                            stopRunNow: stopRunNow
                        });
                    }, this);
                });
            }.bind(this), {
                time: delay,
                source: 'iteration',
                cursor: coords
            }, next);
        }
    }
};