var _ = require('underscore');
var BaseWidget = require('./base');
var debug = require('debug')('windshaft:dataview:histogram');

const columnCastTpl = ctx => `date_part('epoch', ${ctx.column})`;

const dateIntervalQueryTpl = ctx => `
    WITH
    __cdb_dates AS (
        SELECT
            MAX(${ctx.column}::timestamp) AS __cdb_end,
            MIN(${ctx.column}::timestamp) AS __cdb_start
        FROM (${ctx.query}) __cdb_source
    ),
    __cdb_interval_in_days AS (
        SELECT
            DATE_PART('day', __cdb_end - __cdb_start) AS __cdb_days
        FROM __cdb_dates
    ),
    __cdb_interval_in_hours AS (
        SELECT
            __cdb_days * 24 + DATE_PART('hour', __cdb_end - __cdb_start) AS __cdb_hours
        FROM __cdb_interval_in_days, __cdb_dates
    ),
    __cdb_interval_in_minutes AS (
        SELECT
            __cdb_hours * 60 + DATE_PART('minute', __cdb_end - __cdb_start) AS __cdb_minutes
        FROM __cdb_interval_in_hours, __cdb_dates
    ),
    __cdb_interval_in_seconds AS (
        SELECT
            __cdb_minutes * 60 + DATE_PART('second', __cdb_end - __cdb_start) AS __cdb_seconds
        FROM __cdb_interval_in_minutes, __cdb_dates
    )
    SELECT
        ROUND(__cdb_days / 365) AS year,
        ROUND(__cdb_days / 90) AS quarter,
        ROUND(__cdb_days / 30) AS month,
        ROUND(__cdb_days / 7) AS week,
        __cdb_days AS day,
        __cdb_hours AS hour,
        __cdb_minutes AS minute,
        __cdb_seconds AS second
    FROM __cdb_interval_in_days, __cdb_interval_in_hours, __cdb_interval_in_minutes, __cdb_interval_in_seconds
`;

var MAX_INTERVAL_VALUE = 366;
var BIN_MIN_NUMBER = 6;
var BIN_MAX_NUMBER = 48;

const filterOutSpecialNumericValues = ctx => `
        ${ctx._column} != 'infinity'::float
    AND
        ${ctx._column} != '-infinity'::float
    AND
        ${ctx._column} != 'NaN'::float
`;

const filteredQueryTpl = ctx => `
    __cdb_filtered_source AS (
        SELECT *
        FROM (${ctx._query}) __cdb_filtered_source_query
        WHERE ${ctx._column} IS NOT NULL
        ${ctx._isFloatColumn ? `AND ${filterOutSpecialNumericValues(ctx)}` : ''}
    )
`;

const basicsQueryTpl = ctx => `
    __cdb_basics AS (
        SELECT
            max(${ctx._column}) AS __cdb_max_val, min(${ctx._column}) AS __cdb_min_val,
            avg(${ctx._column}) AS __cdb_avg_val, count(1) AS __cdb_total_rows
        FROM __cdb_filtered_source
    )
`;

const overrideBasicsQueryTpl = ctx => `
    __cdb_basics AS (
        SELECT
            max(${ctx._end}) AS __cdb_max_val, min(${ctx._start}) AS __cdb_min_val,
            avg(${ctx._column}) AS __cdb_avg_val, count(1) AS __cdb_total_rows
        FROM __cdb_filtered_source
    )
`;

const iqrQueryTpl = ctx => `
    __cdb_iqrange AS (
        SELECT max(quartile_max) - min(quartile_max) AS __cdb_iqr
        FROM (
            SELECT quartile, max(_cdb_iqr_column) AS quartile_max from (
                SELECT ${ctx._column} AS _cdb_iqr_column, ntile(4) over (order by ${ctx._column}
            ) AS quartile
            FROM __cdb_filtered_source) _cdb_quartiles
            WHERE quartile = 1 or quartile = 3
            GROUP BY quartile
        ) __cdb_iqr
    )
`;

const binsQueryTpl = ctx => `
    __cdb_bins AS (
        SELECT
            CASE WHEN __cdb_total_rows = 0 OR __cdb_iqr = 0
            THEN 1
            ELSE GREATEST(
                LEAST(${ctx._minBins}, CAST(__cdb_total_rows AS INT)),
                LEAST(
                    CAST(((__cdb_max_val - __cdb_min_val) / (2 * __cdb_iqr * power(__cdb_total_rows, 1/3))) AS INT),
                    ${ctx._maxBins}
                )
            )
        END AS __cdb_bins_number
        FROM __cdb_basics, __cdb_iqrange, __cdb_filtered_source
        LIMIT 1
    )
`;

const overrideBinsQueryTpl = ctx => `
    __cdb_bins AS (
        SELECT ${ctx._bins} AS __cdb_bins_number
    )
`;

const nullsQueryTpl = ctx => `
    __cdb_nulls AS (
        SELECT
            count(*) AS __cdb_nulls_count
        FROM (${ctx._query}) __cdb_histogram_nulls
        WHERE ${ctx._column} IS NULL
    )
`;

const infinitiesQueryTpl = ctx => `
    __cdb_infinities AS (
        SELECT
            count(*) AS __cdb_infinities_count
        FROM (${ctx._query}) __cdb_infinities_query
        WHERE
            ${ctx._column} = 'infinity'::float
        OR
            ${ctx._column} = '-infinity'::float
    )
`;

const nansQueryTpl = ctx => `
    __cdb_nans AS (
        SELECT
            count(*) AS __cdb_nans_count
        FROM (${ctx._query}) __cdb_nans_query
        WHERE ${ctx._column} = 'NaN'::float
    )
`;

const specialNumericValuesColumnDefinitionTpl = () => `
    __cdb_infinities_count AS infinities_count,
    __cdb_nans_count AS nans_count
`;

const specialNumericValuesCTETpl = () => `
    __cdb_infinities, __cdb_nans
`;

const specialNumericValuesColumnTpl = () => `
    infinities_count, nans_count
`;

const histogramQueryTpl = ctx => `
    SELECT
        (__cdb_max_val - __cdb_min_val) / cast(__cdb_bins_number as float) AS bin_width,
        __cdb_bins_number AS bins_number,
        __cdb_nulls_count AS nulls_count,
        ${ctx._isFloatColumn ? `${specialNumericValuesColumnDefinitionTpl()},` : ''}
        __cdb_avg_val AS avg_val,
        CASE WHEN __cdb_min_val = __cdb_max_val
            THEN 0
            ELSE GREATEST(
                1,
                LEAST(
                    WIDTH_BUCKET(${ctx._column}, __cdb_min_val, __cdb_max_val, __cdb_bins_number),
                    __cdb_bins_number
                )
            ) - 1
        END AS bin,
        min(${ctx._column})::numeric AS min,
        max(${ctx._column})::numeric AS max,
        avg(${ctx._column})::numeric AS avg,
        count(*) AS freq
    FROM __cdb_filtered_source, __cdb_basics, __cdb_nulls, __cdb_bins
        ${ctx._isFloatColumn ? `, ${specialNumericValuesCTETpl()}` : ''}
    GROUP BY bin, bins_number, bin_width, nulls_count, avg_val
        ${ctx._isFloatColumn ? `, ${specialNumericValuesColumnTpl()}` : ''}
    ORDER BY bin
`;

const dateBasicsQueryTpl = ctx => `
    __cdb_basics AS (
        SELECT
            max(date_part('epoch', ${ctx._column})) AS __cdb_max_val,
            min(date_part('epoch', ${ctx._column})) AS __cdb_min_val,
            avg(date_part('epoch', ${ctx._column})) AS __cdb_avg_val,
            min(
                date_trunc(
                    '${ctx._aggregation}', ${ctx._column}::timestamp AT TIME ZONE '${ctx._offset}'
                )
            ) AS __cdb_start_date,
            max(${ctx._column}::timestamp AT TIME ZONE '${ctx._offset}') AS __cdb_end_date,
            count(1) AS __cdb_total_rows
        FROM (${ctx._query}) __cdb_basics_query
    )
`;

const dateOverrideBasicsQueryTpl = ctx => `
    __cdb_basics AS (
        SELECT
            max(${ctx._end}) AS __cdb_max_val,
            min(${ctx._start}) AS __cdb_min_val,
            avg(date_part('epoch', ${ctx._column})) AS __cdb_avg_val,
            min(
                date_trunc(
                    '${ctx._aggregation}',
                    TO_TIMESTAMP(${ctx._start})::timestamp AT TIME ZONE '${ctx._offset}'
                )
            ) AS __cdb_start_date,
            max(
                TO_TIMESTAMP(${ctx._end})::timestamp AT TIME ZONE '${ctx._offset}'
            ) AS __cdb_end_date,
            count(1) AS __cdb_total_rows
        FROM (${ctx._query}) __cdb_basics_query
    )
`;

const dateBinsQueryTpl = ctx => `
    __cdb_bins AS (
        SELECT
            __cdb_bins_array,
            ARRAY_LENGTH(__cdb_bins_array, 1) AS __cdb_bins_number
        FROM (
            SELECT
                ARRAY(
                    SELECT GENERATE_SERIES(
                        __cdb_start_date::timestamptz,
                        __cdb_end_date::timestamptz,
                        ${ctx._aggregation === 'quarter' ? `'3 month'::interval` : `'1 ${ctx._aggregation}'::interval`}
                    )
                ) AS __cdb_bins_array
            FROM __cdb_basics
        ) __cdb_bins_array_query
    )
`;

const dateHistogramQueryTpl = ctx => `
    SELECT
        (__cdb_max_val - __cdb_min_val) / cast(__cdb_bins_number as float) AS bin_width,
        __cdb_bins_number AS bins_number,
        __cdb_nulls_count AS nulls_count,
        CASE WHEN __cdb_min_val = __cdb_max_val
        THEN 0
        ELSE GREATEST(
            1,
            LEAST(
                WIDTH_BUCKET(
                    ${ctx._column}::timestamp AT TIME ZONE '${ctx._offset}',
                    __cdb_bins_array
                ),
                __cdb_bins_number
            )
        ) - 1
        END AS bin,
        min(
            date_part(
                'epoch',
                date_trunc(
                    '${ctx._aggregation}', ${ctx._column}::timestamp AT TIME ZONE '${ctx._offset}'
                ) AT TIME ZONE '${ctx._offset}'
            )
        )::numeric AS timestamp,
        date_part('epoch', __cdb_start_date)::numeric AS timestamp_start,
        min(date_part('epoch', ${ctx._column}))::numeric AS min,
        max(date_part('epoch', ${ctx._column}))::numeric AS max,
        avg(date_part('epoch', ${ctx._column}))::numeric AS avg,
        count(*) AS freq
    FROM (${ctx._query}) __cdb_histogram, __cdb_basics, __cdb_bins, __cdb_nulls
    WHERE date_part('epoch', ${ctx._column}) IS NOT NULL
    GROUP BY bin, bins_number, bin_width, nulls_count, timestamp_start
    ORDER BY bin
`;

var TYPE = 'histogram';

/**
Numeric histogram:
{
    type: 'histogram',
    options: {
        column: 'name', // column data type: numeric
        bins: 10 // OPTIONAL
    }
}

Time series:
{
    type: 'histogram',
    options: {
        column: 'date', // column data type: date
        aggregation: 'day' // OPTIONAL (if undefined then it'll be built as numeric)
        offset: -7200 // OPTIONAL (UTC offset in seconds)
    }
 }
 */
function Histogram(query, options, queries) {
    if (!_.isString(options.column)) {
        throw new Error('Histogram expects `column` in widget options');
    }

    this.query = query;
    this.queries = queries;
    this.column = options.column;
    this.bins = options.bins;
    this.aggregation = options.aggregation;
    this.offset = options.offset;

    this._columnType = null;
}

Histogram.prototype = new BaseWidget();
Histogram.prototype.constructor = Histogram;

module.exports = Histogram;

Histogram.prototype.sql = function(psql, override, callback) {
    var self = this;

    if (!callback) {
        callback = override;
        override = {};
    }

    if (this._columnType === null) {
        this.getColumnType(psql, this.column, this.queries.no_filters, function (err, type) {
            // assume numeric, will fail later
            self._columnType = 'numeric';
            if (!err && !!type) {
                self._columnType = Object.keys(type).find(function (key) {
                    return type[key];
                });
            }
            self.sql(psql, override, callback);
        }, true); // use read-only transaction
        return null;
    }

    this._buildQuery(psql, override, callback);
};

Histogram.prototype.isDateHistogram = function (override) {
    return this._columnType === 'date' && (this.aggregation !== undefined || override.aggregation !== undefined);
};

Histogram.prototype._buildQuery = function (psql, override, callback) {
    var filteredQuery, basicsQuery, binsQuery;
    var _column = this.column;
    var _query = this.query;

    if (this.isDateHistogram(override)) {
        return this._buildDateHistogramQuery(psql, override, callback);
    }

    if (this._columnType === 'date') {
        _column = columnCastTpl({column: _column});
    }

    filteredQuery = filteredQueryTpl({
        _isFloatColumn: this._columnType === 'float',
        _query: _query,
        _column: _column
    });

    if (this._shouldOverride(override)) {
        debug('overriding with %j', override);
        basicsQuery = overrideBasicsQueryTpl({
            _query: _query,
            _column: _column,
            _start: getBinStart(override),
            _end: getBinEnd(override)
        });

        binsQuery = [
            overrideBinsQueryTpl({
                _bins: override.bins
            })
        ].join(',\n');
    } else {
        basicsQuery = basicsQueryTpl({
            _query: _query,
            _column: _column
        });

        if (this._shouldOverrideBins(override)) {
            binsQuery = [
                overrideBinsQueryTpl({
                    _bins: override.bins
                })
            ].join(',\n');
        } else {
            binsQuery = [
                iqrQueryTpl({
                    _query: _query,
                    _column: _column
                }),
                binsQueryTpl({
                    _query: _query,
                    _minBins: BIN_MIN_NUMBER,
                    _maxBins: BIN_MAX_NUMBER
                })
            ].join(',\n');
        }
    }

    var cteSql = [
        filteredQuery,
        basicsQuery,
        binsQuery,
        nullsQueryTpl({
            _query: _query,
            _column: _column
        })
    ];

    if (this._columnType === 'float') {
        cteSql.push(
            infinitiesQueryTpl({
                _query: _query,
                _column: _column
            }),
            nansQueryTpl({
                _query: _query,
                _column: _column
            })
        );
    }

    var histogramSql = [
        "WITH",
        cteSql.join(',\n'),
        histogramQueryTpl({
            _isFloatColumn: this._columnType === 'float',
            _query: _query,
            _column: _column
        })
    ].join('\n');

    debug(histogramSql);

    return callback(null, histogramSql);
};

Histogram.prototype._shouldOverride = function (override) {
    return override && _.has(override, 'start') && _.has(override, 'end') && _.has(override, 'bins');
};

Histogram.prototype._shouldOverrideBins = function (override) {
    return override && _.has(override, 'bins');
};

var DATE_AGGREGATIONS = {
    'auto': true,
    'minute': true,
    'hour': true,
    'day': true,
    'week': true,
    'month': true,
    'quarter': true,
    'year': true
};

Histogram.prototype._buildDateHistogramQuery = function (psql, override, callback) {
    var _column = this.column;
    var _query = this.query;
    var _aggregation = override && override.aggregation ? override.aggregation : this.aggregation;
    var _offset = override && Number.isFinite(override.offset) ? override.offset : this.offset;

    if (!DATE_AGGREGATIONS.hasOwnProperty(_aggregation)) {
        return callback(new Error('Invalid aggregation value. Valid ones: ' +
            Object.keys(DATE_AGGREGATIONS).join(', ')
        ));
    }

    if (_aggregation === 'auto') {
        this.getAutomaticAggregation(psql, function (err, aggregation) {
            if (err || aggregation === 'none') {
                this.aggregation = 'day';
            } else {
                this.aggregation = aggregation;
            }
            override.aggregation = this.aggregation;
            this._buildDateHistogramQuery(psql, override, callback);
        }.bind(this));
        return null;
    }

    var dateBasicsQuery;

    if (override && _.has(override, 'start') && _.has(override, 'end')) {
        dateBasicsQuery = dateOverrideBasicsQueryTpl({
            _query: _query,
            _column: _column,
            _aggregation: _aggregation,
            _start: getBinStart(override),
            _end: getBinEnd(override),
            _offset: parseOffset(_offset, _aggregation)
        });
    } else {
        dateBasicsQuery = dateBasicsQueryTpl({
            _query: _query,
            _column: _column,
            _aggregation: _aggregation,
            _offset: parseOffset(_offset, _aggregation)
        });
    }

    var dateBinsQuery = [
        dateBinsQueryTpl({
            _aggregation: _aggregation
        })
    ].join(',\n');

    var nullsQuery = nullsQueryTpl({
        _query: _query,
        _column: _column
    });

    var dateHistogramQuery = dateHistogramQueryTpl({
        _query: _query,
        _column: _column,
        _aggregation: _aggregation,
        _offset: parseOffset(_offset, _aggregation)
    });

    var histogramSql = [
        "WITH",
        [
            dateBasicsQuery,
            dateBinsQuery,
            nullsQuery
        ].join(',\n'),
        dateHistogramQuery
    ].join('\n');

    debug(histogramSql);

    return callback(null, histogramSql);
};

Histogram.prototype.getAutomaticAggregation = function (psql, callback) {
    var dateIntervalQuery = dateIntervalQueryTpl({
        query: this.query,
        column: this.column
    });

    debug(dateIntervalQuery);

    psql.query(dateIntervalQuery, function (err, result) {
        if (err) {
            return callback(err);
        }

        var aggegations = result.rows[0];
        var aggregation = Object.keys(aggegations)
            .map(function (key) {
                return {
                    name: key,
                    value: aggegations[key]
                };
            })
            .reduce(function (closer, current) {
                if (current.value > MAX_INTERVAL_VALUE) {
                    return closer;
                }

                var closerDiff = MAX_INTERVAL_VALUE - closer.value;
                var currentDiff = MAX_INTERVAL_VALUE - current.value;

                if (Number.isFinite(current.value) && closerDiff > currentDiff) {
                    return current;
                }

                return closer;
            }, { name: 'none', value: -1 });

        callback(null, aggregation.name);
    });
};

Histogram.prototype.format = function(result, override) {
    override = override || {};
    var buckets = [];

    var binsCount = getBinsCount(override);
    var width = getWidth(override);
    var binsStart = getBinStart(override);
    var nulls = 0;
    var infinities = 0;
    var nans = 0;
    var avg;
    var timestampStart;
    var aggregation;
    var offset;

    if (result.rows.length) {
        var firstRow = result.rows[0];
        binsCount = firstRow.bins_number;
        width = firstRow.bin_width || width;
        avg = firstRow.avg_val;
        nulls = firstRow.nulls_count;
        timestampStart = firstRow.timestamp_start;
        infinities = firstRow.infinities_count;
        nans = firstRow.nans_count;
        binsStart = populateBinStart(override, firstRow);

        if (Number.isFinite(timestampStart)) {
            aggregation = getAggregation(override, this.aggregation);
            offset = getOffset(override, this.offset);
        }

        buckets = result.rows.map(function(row) {
            return _.omit(
                row,
                'bins_number',
                'bin_width',
                'nulls_count',
                'infinities_count',
                'nans_count',
                'avg_val',
                'timestamp_start'
            );
        });
    }

    return {
        aggregation: aggregation,
        offset: offset,
        timestamp_start: timestampStart,
        bin_width: width,
        bins_count: binsCount,
        bins_start: binsStart,
        nulls: nulls,
        infinities: infinities,
        nans: nans,
        avg: avg,
        bins: buckets
    };
};

function getAggregation(override, aggregation) {
    return override && override.aggregation ? override.aggregation : aggregation;
}

function getOffset(override, offset) {
    if (override && override.offset) {
        return override.offset;
    }
    if (offset) {
        return offset;
    }

    return 0;
}

function getBinStart(override) {
    if (override.hasOwnProperty('start') && override.hasOwnProperty('end')) {
        return Math.min(override.start, override.end);
    }
    return override.start || 0;
}

function getBinEnd(override) {
    if (override.hasOwnProperty('start') && override.hasOwnProperty('end')) {
        return Math.max(override.start, override.end);
    }
    return override.end || 0;
}

function getBinsCount(override) {
    return override.bins || 0;
}

function getWidth(override) {
    var width = 0;
    var binsCount = override.bins;

    if (binsCount && Number.isFinite(override.start) && Number.isFinite(override.end)) {
        width = (override.end - override.start) / binsCount;
    }

    return width;
}

function parseOffset(offset, aggregation) {
    if (!offset) {
        return '0';
    }
    if (aggregation === 'hour' || aggregation === 'minute') {
        return '0';
    }

    var offsetInHours = Math.ceil(offset / 3600);
    return '' + offsetInHours;
}

function populateBinStart(override, firstRow) {
    var binStart;

    if (firstRow.hasOwnProperty('timestamp')) {
        binStart = firstRow.timestamp;
    } else if (override.hasOwnProperty('start')) {
        binStart = getBinStart(override);
    } else {
        binStart = firstRow.min;
    }

    return binStart;
}

Histogram.prototype.getType = function() {
    return TYPE;
};

Histogram.prototype.toString = function() {
    return JSON.stringify({
        _type: TYPE,
        _column: this.column,
        _query: this.query
    });
};