'use strict';

var crypto = require('crypto');
var step = require('step');
var fs = require('fs');
var _ = require('underscore');
var PSQL = require('cartodb-psql');
var spawn = require('child_process').spawn;

// Keeps track of what's waiting baking for export
var bakingExports = {};

function OgrFormat (id) {
    this.id = id;
}

OgrFormat.prototype = {

    id: 'ogr',

    is_file: true,

    getQuery: function (/* sql, options */) {
        return null; // dont execute the query
    },

    transform: function (/* result, options, callback */) {
        throw new Error('should not be called for file formats');
    },

    getContentType: function () { return this._contentType; },

    getFileExtension: function () { return this._fileExtension; },

    getKey: function (options) {
        return [this.id,
            options.dbopts.dbname,
            options.dbopts.user,
            options.gn,
            this.generateMD5(options.filename),
            this.generateMD5(options.sql)].concat(options.skipfields).join(':');
    },

    generateMD5: function (data) {
        var hash = crypto.createHash('md5');
        hash.update(data);
        return hash.digest('hex');
    },

    limitPathname: function (pathname) {
        if (pathname.length < 128) { return pathname; }
        return crypto.createHash('sha256').update(pathname).digest('hex');
    }

};

// Internal function usable by all OGR-driven outputs
OgrFormat.prototype.toOGR = function (options, outFormat, outFilename, callback) {
    // var gcol = options.gn;
    var sql = options.sql;
    var skipfields = options.skipfields;
    var outLayername = options.filename;

    var dbopts = options.dbopts;

    var ogr2ogr = global.settings.ogr2ogrCommand || 'ogr2ogr';
    var dbhost = dbopts.host;
    var dbport = dbopts.port;
    var dbuser = dbopts.user;
    var dbpass = dbopts.pass;
    var dbname = dbopts.dbname;

    var timeout = options.timeout;

    var that = this;

    var columns = [];
    var geocol;
    var pg;
    // Drop ending semicolon (ogr doens't like it)
    sql = sql.replace(/;\s*$/, '');

    const theGeomFirst = (fieldA, fieldB) => {
        if (fieldA.name === 'the_geom') {
            return -1;
        }
        if (fieldB.name === 'the_geom') {
            return 1;
        }
        return 0;
    };

    step(

        function fetchColumns () {
            var colsql = 'SELECT * FROM (' + sql + ') as _cartodbsqlapi LIMIT 0';
            pg = new PSQL(dbopts);
            pg.query(colsql, this);
        },
        function findSRS (err, result) {
            if (err) {
                throw err;
            }

            var needSRS = that._needSRS;

            columns = result.fields
            // skip columns
                .filter(field => skipfields.indexOf(field.name) === -1)
            // put "the_geom" first (if exists)
                .sort(theGeomFirst)
            // get first geometry to calculate SRID ("the_geom" if exists)
                .map(field => {
                    if (needSRS && !geocol && pg.typeName(field.dataTypeID) === 'geometry') {
                        geocol = field.name;
                    }

                    return field;
                })
            // apply quotes to columns
                .map(field => outFormat === 'CSV' ? pg.quoteIdentifier(field.name) + '::text' : pg.quoteIdentifier(field.name));

            if (!needSRS || !geocol) {
                return null;
            }

            var next = this;

            var qgeocol = pg.quoteIdentifier(geocol);
            var sridsql = 'SELECT ST_Srid(' + qgeocol + ') as srid, GeometryType(' +
                   qgeocol + ') as type FROM (' + sql + ') as _cartodbsqlapi WHERE ' +
                   qgeocol + ' is not null limit 1';

            pg.query(sridsql, function (err, result) {
                if (err) { next(err); return; }
                if (result.rows.length) {
                    var srid = result.rows[0].srid;
                    var type = result.rows[0].type;
                    next(null, srid, type);
                } else {
                    // continue as srid and geom type are not critical when there are no results
                    next(null);
                }
            });
        },
        function spawnDumper (err, srid, type) {
            if (err) {
                throw err;
            }

            var next = this;

            var ogrsql = 'SELECT ' + columns.join(',') + ' FROM (' + sql + ') as _cartodbsqlapi';

            var ogrargs = [
                '-f', outFormat,
                '-lco', 'RESIZE=YES', /* shapefile */
                '-lco', 'ENCODING=UTF-8', /* shapefile */
                '-lco', 'STRING_QUOTING=IF_NEEDED', /* csv: Match gdal 2.2 behaviour */
                '-lco', 'LINEFORMAT=CRLF',
                outFilename,
                'PG:host=' + dbhost + ' port=' + dbport + ' user=' + dbuser + ' dbname=' + dbname + ' password=' + dbpass,
                '-sql', ogrsql
            ];

            if (srid) {
                ogrargs.push('-a_srs', 'EPSG:' + srid);
            }

            if (type) {
                ogrargs.push('-nlt', type);
            }

            if (options.cmd_params) {
                ogrargs = ogrargs.concat(options.cmd_params);
            }

            ogrargs.push('-nln', outLayername);

            // TODO: research if `exec` could fit better than `spawn`
            var child = spawn(ogr2ogr, ogrargs);

            var timedOut = false;
            var ogrTimeout;
            if (timeout > 0) {
                ogrTimeout = setTimeout(function () {
                    timedOut = true;
                    child.kill();
                }, timeout);
            }

            child.on('error', function (err) {
                clearTimeout(ogrTimeout);
                next(err);
            });

            var stderrData = [];
            child.stderr.setEncoding('utf8');
            child.stderr.on('data', function (data) {
                stderrData.push(data);
            });

            child.on('exit', function (code) {
                clearTimeout(ogrTimeout);

                if (timedOut) {
                    return next(new Error('statement timeout'));
                }

                if (code !== 0) {
                    var errMessage = 'ogr2ogr command return code ' + code;
                    if (stderrData.length > 0) {
                        errMessage += ', Error: ' + stderrData.join('\n');
                    }

                    return next(new Error(errMessage));
                }

                return next();
            });
        },
        function finish (err) {
            callback(err, outFilename);
        }
    );
};

OgrFormat.prototype.toOGR_SingleFile = function (options, fmt, callback) {
    var dbname = options.dbopts.dbname;
    var userId = options.dbopts.user;
    var gcol = options.gcol;
    var sql = options.sql;
    var skipfields = options.skipfields;
    var ext = this._fileExtension;
    var layername = options.filename;

    var tmpdir = global.settings.tmpDir || '/tmp';
    var reqKey = this.limitPathname([
        fmt,
        dbname,
        userId,
        gcol,
        this.generateMD5(layername),
        this.generateMD5(sql)
    ].concat(skipfields).join(':'));
    var outdirpath = tmpdir + '/sqlapi-' + process.pid + '-' + reqKey;
    var dumpfile = outdirpath + ':cartodb-query.' + ext;

    // TODO: following tests:
    //  - fetch query with no "the_geom" column
    this.toOGR(options, fmt, dumpfile, callback);
};

OgrFormat.prototype.sendResponse = function (opts, callback) {
    // var next = callback;
    var reqKey = this.getKey(opts);
    var qElem = new ExportRequest(opts.sink, callback, opts.beforeSink);
    var baking = bakingExports[reqKey];
    if (baking) {
        baking.req.push(qElem);
    } else {
        baking = bakingExports[reqKey] = { req: [qElem] };
        this.generate(opts, function (err, dumpfile) {
            if (opts.profiler) {
                opts.profiler.done('generate');
            }
            step(
                function sendResults () {
                    var nextPipe = function (finish) {
                        var r = baking.req.shift();
                        if (!r) { finish(null); return; }
                        r.sendFile(err, dumpfile, function () {
                            nextPipe(finish);
                        });
                    };

                    if (!err) {
                        nextPipe(this);
                    } else {
                        _.each(baking.req, function (r) {
                            r.cb(err);
                        });
                        return true;
                    }
                },
                function cleanup (/* err */) {
                    delete bakingExports[reqKey];

                    // unlink dump file (sync to avoid race condition)
                    console.log('removing', dumpfile);
                    try { fs.unlinkSync(dumpfile); } catch (e) {
                        if (e.code !== 'ENOENT') {
                            console.log('Could not unlink dumpfile ' + dumpfile + ': ' + e);
                        }
                    }
                }
            );
        });
    }
};

function ExportRequest (ostream, callback, beforeSink) {
    this.cb = callback;
    this.beforeSink = beforeSink;
    this.ostream = ostream;
    this.istream = null;
    this.canceled = false;

    var that = this;

    this.ostream.on('close', function () {
        that.canceled = true;
        if (that.istream) {
            that.istream.destroy();
        }
    });
}

ExportRequest.prototype.sendFile = function (err, filename, callback) {
    if (err) {
        return callback(err);
    }

    var that = this;
    if (!this.canceled) {
        this.istream = fs.createReadStream(filename)
            .on('open', function (/* fd */) {
                if (that.beforeSink) {
                    that.beforeSink();
                }
                that.istream
                    .pipe(that.ostream)
                    .on('end', () => {
                        callback();
                        that.cb();
                    })
                    .on('error', (err) => {
                        callback();
                        that.cb(err);
                    });
            })
            .on('error', function (e) {
                console.log("Can't send response: " + e);
                that.ostream.end();
                that.cb(e);
                callback();
            })
            .on('end', () => {
                that.cb();
                callback();
            });
    } else {
        callback();
    }
};

module.exports = OgrFormat;