// Простенький "селект билдер" по мотивам MediaWiki-овского, успешно юзаю подобный в PHP уже лет 8
// (c) Виталий Филиппов, 2019
// Версия 2019-05-14

// В PHP, правда, прикольнее - там в массиве можно смешивать строковые и численные ключи,
// благодаря чему можно писать $where = [ 't1.a=t2.a', 't2.b' => [ 1, 2, 3 ] ]
// Здесь так нельзя, поэтому этот синтаксис мы заменяем на { 't1.a=t2.a': [], 't2.b': [ 1, 2, 3 ] }

const pg = require('pg');

// Сраный node-postgres конвертирует даты в Date и портит таймзону
const DATATYPE_DATE = 1082;
pg.types.setTypeParser(DATATYPE_DATE, function(val)
{
    return val === null ? null : val;
});

let pg_escape;

const MS_HASH = 0;
const MS_LIST = 1;
const MS_ROW = 2;
const MS_COL = 4;
const MS_VALUE = 6;

function select_builder(tables, fields, where, options)
{
    let sql = 'SELECT ', bind = [];
    if (fields instanceof Array)
    {
        sql += fields.join(', ');
    }
    else if (typeof fields == 'string')
    {
        sql += fields;
    }
    else if (typeof fields == 'object')
    {
        sql += Object.keys(fields).map(k => fields[k]+' AS '+k).join(', ');
    }
    else
    {
        throw new Error('fields = '+fields+' is invalid');
    }
    sql += ' FROM ';
    const t = tables_builder(tables);
    sql += t.sql;
    bind.push.apply(bind, t.bind);
    where = where_builder(where);
    sql += ' WHERE '+(where.sql || '1=1');
    bind.push.apply(bind, where.bind);
    if (t.moreWhere)
    {
        sql += ' AND '+t.moreWhere.sql;
        bind.push.apply(bind, t.moreWhere.bind);
    }
    options = options||{};
    if (options['GROUP BY'] || options.group_by)
    {
        let group = options['GROUP BY'] || options.group_by;
        group = group instanceof Array ? group : [ group ];
        sql += ' GROUP BY '+group.join(', ');
    }
    if (options['ORDER BY'] || options.order_by)
    {
        let order = options['ORDER BY'] || options.order_by;
        order = order instanceof Array ? order : [ order ];
        sql += ' ORDER BY '+order.join(', ');
    }
    if (options.LIMIT || options.limit)
    {
        sql += ' LIMIT '+((options.LIMIT || options.limit) | 0);
    }
    if (options.OFFSET || options.offset)
    {
        sql += ' OFFSET '+((options.OFFSET || options.offset) | 0);
    }
    return new Text(sql, bind);
}

function tables_builder(tables)
{
    let sql = '', bind = [];
    let moreWhere = null;
    let first = true;
    if (typeof tables == 'string')
    {
        sql = tables;
        return { sql, bind, moreWhere };
    }
    for (const k in tables)
    {
        let jointype = 'INNER', table = tables[k], conds = null;
        if (table instanceof Array)
        {
            [ jointype, table, conds ] = table;
        }
        if (!first)
        {
            sql += ' ' + jointype.toUpperCase() + ' JOIN ';
        }
        let more_on;
        if (table instanceof Pg_Values)
        {
            sql += '(VALUES ';
            let i = 0;
            for (const row of table.rows)
            {
                sql += (i > 0 ? ', (' : '(') + table.keys.map(() => '?').join(', ')+')';
                bind.push.apply(bind, table.keys.map(k => row[k]));
                i++;
            }
            sql += ') AS '+k+'('+table.keys.join(', ')+')';
        }
        else if (typeof table == 'object')
        {
            // Nested join, `k` alias is ignored
            let subjoin = tables_builder(table);
            if (subjoin.moreWhere)
            {
                more_on = subjoin.moreWhere;
            }
            if (Object.keys(table).length > 1)
            {
                sql += "("+subjoin.sql+")";
            }
            else
            {
                sql += subjoin.sql;
            }
            bind.push.apply(subjoin.bind);
        }
        else
        {
            sql += table + ' ' + k;
        }
        conds = where_builder(conds);
        if (more_on)
        {
            if (!conds.sql)
                conds = more_on;
            else
            {
                conds.sql += ' AND ' + more_on.sql;
                conds.bind.push.apply(conds.bind, more_on.bind);
            }
        }
        if (!first)
        {
            sql += ' ON ' + (conds.sql || '1=1');
            bind.push.apply(bind, conds.bind);
        }
        else
        {
            // Бывает удобно указывать WHERE как условие "JOIN" первой таблицы
            moreWhere = conds.sql ? conds : null;
            first = false;
        }
    }
    return { sql, bind, moreWhere };
}

// fields: one of:
// - string: 'a=b AND c=d'
// - array: [ 'a=b', [ 'a=? or b=?', 1, 2 ], [ 'a', [ 1, 2 ] ] ]
// - object: { a: 1, b: [ 1, 2 ], 'a = b': [], '(a, b)': [ [ 1, 2 ], [ 2, 3 ] ], 'c=? or d=?': [ 2, 3 ] }
//   - key does not contain '?', value is a scalar or non-empty array => (key IN ...)
//   - key does not contain '?', value is an empty array => just (key)
//   - key contains '?', value is a scalar or non-empty array => (key) with bind params (...value)
//   - key is numeric, then value is treated as in array
function where_or_set(fields, where)
{
    if (typeof fields == 'string')
    {
        return { sql: fields, bind: [] };
    }
    const w = [], bind = [];
    for (let k in fields)
    {
        let v = fields[k];
        if (/^\d+$/.exec(k))
        {
            if (v instanceof Array)
            {
                k = v[0];
                v = v.slice(1);
            }
            else
            {
                w.push(v);
                continue;
            }
        }
        if (k.indexOf('?') >= 0 || v instanceof Array && v.length == 0)
        {
            if (!(v instanceof Array))
            {
                v = [ v ];
            }
            // FIXME: check bind variable count
            w.push(k);
            bind.push.apply(bind, v);
            continue;
        }
        v = v instanceof Array ? v : [ v ];
        if (v.length == 1 && v[0] == null)
        {
            w.push(where ? k+' is null' : k+' = null');
        }
        else
        {
            if ((v.length > 1 || v[0] instanceof Array) && !where)
            {
                throw new Error('IN syntax can only be used inside WHERE');
            }
            if (v[0] instanceof Array)
            {
                // (a, b) in (...)
                w.push(k + ' in (' + v.map(vi => '('+vi.map(() => '?').join(', ')+')') + ')');
                v.map(vi => bind.push.apply(bind, vi));
            }
            else
            {
                w.push(v.length == 1
                    ? k + ' = ?'
                    : k + ' in (' + v.map(() => '?').join(', ') + ')');
                bind.push.apply(bind, v);
            }
        }
    }
    if (!where)
    {
        // SET
        return { sql: w.join(', '), bind };
    }
    // WHERE
    return { sql: w.length ? '('+w.join(') and (')+')' : '', bind };
}

function where_builder(where)
{
    return where_or_set(where, true);
}

/**
 * Разбивает набор таблиц на основную обновляемую + набор дополнительных
 *
 * Идея в том, чтобы обрабатывать хотя бы 2 простые ситуации:
 * UPDATE table1 INNER JOIN table2 ...
 * UPDATE table1 LEFT JOIN table2 ...
 */
function split_using(tables)
{
    if (typeof tables == 'string')
    {
        return { what: { sql: tables, bind: [] }, using: null, moreWhere: null };
    }
    let first = null;
    let is_next_inner = true;
    let i = 0;
    for (let k in tables)
    {
        let t = tables[k];
        if (i == 0)
        {
            if (t instanceof Array && typeof(t[1]) != 'string')
            {
                throw new Error('Can only update/delete from real tables, not sub-select, sub-join or VALUES');
            }
            first = k;
        }
        else if (i == 1)
        {
            is_next_inner = !(t instanceof Array) || t[0].toLowerCase() == 'inner';
        }
        else
        {
            break;
        }
        i++;
    }
    let what, moreWhere;
    if (is_next_inner)
    {
        what = tables_builder({ [first]: tables[first] });
        delete tables[first];
        moreWhere = what.moreWhere;
        what.moreWhere = null;
    }
    else
    {
        what = tables_builder({ ["_"+first]: tables[first] });
        const cond = '_'+first+'.ctid='+(/^\d+$/.exec(first) ? tables[first] : first)+'.ctid';
        moreWhere = what.moreWhere
            ? { sql: what.moreWhere.sql+' AND '+cond, bind: what.moreWhere.bind }
            : { sql: cond, bind: [] };
        what.moreWhere = null;
    }
    return { what, using: Object.keys(tables).length > 0 ? tables : null, moreWhere };
}

function _positional(sql)
{
    let i = 0;
    sql = sql.replace(/'(?:[^\']*|\'\')*'|"(?:[^\"]*|\"\")*"|(\?)/g, (m, m1) => (m1 ? '$'+(++i) : m));
    console.log('> '+sql);
    return sql;
}

function _inline(sql, bind)
{
    if (!pg_escape)
    {
        pg_escape = require('pg-escape');
    }
    let i = 0;
    sql = sql.replace(/'(?:[^\']*|\'\')*'|"(?:[^\"]*|\"\")*"|(\?)/g, (m, m1) => (m1 ? '\''+pg_escape.string(bind[i++])+'\'' : m));
    return sql;
}

// dbh = node-postgres.Client
async function select(dbh, tables, fields, where, options, format)
{
    let { sql, bind } = select_builder(tables, fields, where, options);
    let data = await dbh.query(_positional(sql), bind);
    if ((format & MS_LIST) || (format & MS_COL))
        data = data.rows.map(r => Object.values(r));
    else
        data = data.rows;
    if (format & MS_ROW)
        data = data[0];
    if (data && (format & MS_COL))
        data = data[0];
    return data;
}

async function insert(dbh, table, rows, options)
{
    if (!(rows instanceof Array))
    {
        rows = [ rows ];
    }
    if (!rows.length)
    {
        return null;
    }
    const keys = Object.keys(rows[0]);
    let sql = 'insert into '+table+' ('+keys.join(', ')+') values ';
    const bind = [];
    let i = 0;
    for (const row of rows)
    {
        sql += (i > 0 ? ', (' : '(') + keys.map(() => '$'+(++i)).join(', ')+')';
        bind.push.apply(bind, keys.map(k => row[k]));
    }
    if (options && options.returning)
    {
        sql += ' returning '+options.returning;
        return (await dbh.query(sql, bind)).rows;
    }
    return await dbh.query(sql, bind);
}

async function _delete(dbh, table, where, options)
{
    where = where_builder(where);
    const split = split_using(table);
    if (split.using)
    {
        split.using = tables_builder(split.using);
    }
    let sql = 'delete from '+split.what.sql+
        (split.using ? ' using '+split.using.sql : '')+
        ' where '+(where.sql || '1=1')+(split.moreWhere ? ' and '+split.moreWhere.sql : '');
    let bind = [ ...split.what.bind, ...where.bind, ...(split.moreWhere ? split.moreWhere.bind : []) ];
    if (options && options.returning)
    {
        sql += ' returning '+options.returning;
        return (await dbh.query(_positional(sql), bind)).rows;
    }
    return await dbh.query(_positional(sql), bind);
}

async function update(dbh, table, set, where, options)
{
    set = where_or_set(set, false);
    where = where_builder(where);
    const split = split_using(table);
    if (split.using)
    {
        split.using = tables_builder(split.using);
    }
    let sql = 'update '+split.what.sql+' set '+set.sql+
        (split.using ? ' from '+split.using.sql : '')+
        ' where '+(where.sql || '1=1')+(split.moreWhere ? ' and '+split.moreWhere.sql : '');
    let bind = [
        ...split.what.bind,
        ...set.bind,
        ...(split.using ? split.using.bind : []),
        ...where.bind,
        ...(split.moreWhere ? split.moreWhere.bind : [])
    ];
    if (options && options.returning)
    {
        sql += ' returning '+options.returning;
        return (await dbh.query(_positional(sql), bind)).rows;
    }
    return await dbh.query(_positional(sql), bind);
}

function values(rows)
{
    return new Pg_Values(Object.keys(rows[0]), rows);
}

class Pg_Values
{
    constructor(keys, rows)
    {
        this.keys = keys;
        this.rows = rows;
    }
}

class Text
{
    constructor(sql, bind)
    {
        this.sql = sql;
        this.bind = bind || [];
    }

    toString()
    {
        return _inline(this.sql, this.bind);
    }

    concat(text)
    {
        return new Text(this.sql+text.sql, [ ...this.bind, ...text.bind ]);
    }
}

module.exports = {
    select_builder,
    where_builder,
    quote_into: _inline,
    quote_positional: _positional,
    select,
    insert,
    delete: _delete,
    update,
    values,
    Text,
    MS_HASH,
    MS_LIST,
    MS_ROW,
    MS_COL,
    MS_VALUE,
};