const frappe = require('frappejs');
const Observable = require('frappejs/utils/observable');

module.exports = class Database extends Observable {
  constructor() {
    super();
    this.initTypeMap();
  }

  async connect() {
    // this.conn
  }

  close() {
    this.conn.close();
  }

  async migrate() {
    for (let doctype in frappe.models) {
      // check if controller module
      let meta = frappe.getMeta(doctype);
      if (!meta.isSingle) {
        if (await this.tableExists(doctype)) {
          await this.alterTable(doctype);
        } else {
          await this.createTable(doctype);
        }
      }
    }
    await this.commit();
  }

  async createTable(doctype, newName = null) {
    let meta = frappe.getMeta(doctype);
    let columns = [];
    let indexes = [];

    for (let field of meta.getValidFields({ withChildren: false })) {
      if (this.typeMap[field.fieldtype]) {
        this.updateColumnDefinition(field, columns, indexes);
      }
    }

    return await this.runCreateTableQuery(newName || doctype, columns, indexes);
  }

  async tableExists(table) {
    // return true if table exists
  }

  async runCreateTableQuery(doctype, columns, indexes) {
    // override
  }

  updateColumnDefinition(field, columns, indexes) {
    // return `${df.fieldname} ${this.typeMap[df.fieldtype]} ${ ? "PRIMARY KEY" : ""} ${df.required && !df.default ? "NOT NULL" : ""} ${df.default ? `DEFAULT ${df.default}` : ""}`
  }

  async alterTable(doctype) {
    // get columns
    let diff = await this.getColumnDiff(doctype);
    let newForeignKeys = await this.getNewForeignKeys(doctype);

    if (diff.added.length) {
      await this.addColumns(doctype, diff.added);
    }

    if (diff.removed.length) {
      await this.removeColumns(doctype, diff.removed);
    }

    if (newForeignKeys.length) {
      await this.addForeignKeys(doctype, newForeignKeys);
    }
  }

  async getColumnDiff(doctype) {
    const tableColumns = await this.getTableColumns(doctype);
    const validFields = frappe.getMeta(doctype).getValidFields({ withChildren: false });
    const diff = { added: [], removed: [] };

    for (let field of validFields) {
      if (!tableColumns.includes(field.fieldname) && this.typeMap[field.fieldtype]) {
        diff.added.push(field);
      }
    }

    const validFieldNames = validFields.map(field => field.fieldname);
    for (let column of tableColumns) {
      if (!validFieldNames.includes(column)) {
        diff.removed.push(column);
      }
    }

    return diff;
  }

  async addColumns(doctype, added) {
    for (let field of added) {
      await this.runAddColumnQuery(doctype, field);
    }
  }

  async removeColumns(doctype, removed) {
    for (let column of removed) {
      await this.runRemoveColumnQuery(doctype, column);
    }
  }


  async getNewForeignKeys(doctype) {
    let foreignKeys = await this.getForeignKeys(doctype);
    let newForeignKeys = [];
    let meta = frappe.getMeta(doctype);
    for (let field of meta.getValidFields({ withChildren: false })) {
      if (field.fieldtype === 'Link' && !foreignKeys.includes(field.fieldname)) {
        newForeignKeys.push(field);
      }
    }
    return newForeignKeys;
  }

  async addForeignKeys(doctype, newForeignKeys) {
    for (let field of newForeignKeys) {
      this.addForeignKey(doctype, field);
    }
  }

  async getForeignKey(doctype, field) {

  }

  async getTableColumns(doctype) {
    return [];
  }

  async runAddColumnQuery(doctype, field) {
    // alter table {doctype} add column ({column_def});
  }

  async get(doctype, name = null, fields = '*') {
    let meta = frappe.getMeta(doctype);
    let doc;
    if (meta.isSingle) {
      doc = await this.getSingle(doctype);
      doc.name = doctype;
    } else {
      if (!name) {
        throw new frappe.errors.ValueError('name is mandatory');
      }
      doc = await this.getOne(doctype, name, fields);
    }
    await this.loadChildren(doc, meta);
    return doc;
  }

  async loadChildren(doc, meta) {
    // load children
    let tableFields = meta.getTableFields();
    for (let field of tableFields) {
      doc[field.fieldname] = await this.getAll({
        doctype: field.childtype,
        fields: ["*"],
        filters: { parent: doc.name },
        orderBy: 'idx',
        order: 'asc'
      });
    }
  }

  async getSingle(doctype) {
    let values = await this.getAll({
      doctype: 'SingleValue',
      fields: ['fieldname', 'value'],
      filters: { parent: doctype },
      orderBy: 'fieldname',
      order: 'asc'
    });
    let doc = {};
    for (let row of values) {
      doc[row.fieldname] = row.value;
    }
    return doc;
  }

  async getOne(doctype, name, fields = '*') {
    // select {fields} form {doctype} where name = ?
  }

  prepareFields(fields) {
    if (fields instanceof Array) {
      fields = fields.join(", ");
    }
    return fields;
  }

  triggerChange(doctype, name) {
    this.trigger(`change:${doctype}`, { name }, 500);
    this.trigger(`change`, { doctype, name }, 500);
  }

  async insert(doctype, doc) {
    let meta = frappe.getMeta(doctype);

    // insert parent
    if (meta.isSingle) {
      await this.updateSingle(meta, doc, doctype);
    } else {
      await this.insertOne(doctype, doc);
    }

    // insert children
    await this.insertChildren(meta, doc, doctype);

    this.triggerChange(doctype, doc.name);

    return doc;
  }


  async insertChildren(meta, doc, doctype) {
    let tableFields = meta.getTableFields();
    for (let field of tableFields) {
      let idx = 0;
      for (let child of (doc[field.fieldname] || [])) {
        this.prepareChild(doctype, doc.name, child, field, idx);
        await this.insertOne(field.childtype, child);
        idx++;
      }
    }
  }

  async insertOne(doctype, doc) {
    // insert into {doctype} ({fields}) values ({values})
  }

  async update(doctype, doc) {
    let meta = frappe.getMeta(doctype);

    // update parent
    if (meta.isSingle) {
      await this.updateSingle(meta, doc, doctype);
    } else {
      await this.updateOne(doctype, doc);
    }

    // insert or update children
    await this.updateChildren(meta, doc, doctype);

    this.triggerChange(doctype, doc.name);

    return doc;
  }

  async updateChildren(meta, doc, doctype) {
    let tableFields = meta.getTableFields();
    for (let field of tableFields) {
      // first key is "parent" - for SQL params
      let added = [doc.name];
      for (let child of (doc[field.fieldname] || [])) {
        this.prepareChild(doctype, doc.name, child, field, added.length - 1);
        if (await this.exists(field.childtype, child.name)) {
          await this.updateOne(field.childtype, child);
        }
        else {
          await this.insertOne(field.childtype, child);
        }
        added.push(child.name);
      }
      await this.runDeleteOtherChildren(field, added);
    }
  }

  async updateOne(doctype, doc) {
    // update {doctype} set {field=value} where name=?
  }

  async runDeleteOtherChildren(field, added) {
    // delete from doctype where parent = ? and name not in (?, ?, ?)
  }

  async updateSingle(meta, doc, doctype) {
    await this.deleteSingleValues(doctype);
    for (let field of meta.getValidFields({ withChildren: false })) {
      let value = doc[field.fieldname];
      if (value) {
        let singleValue = frappe.newDoc({
          doctype: 'SingleValue',
          parent: doctype,
          fieldname: field.fieldname,
          value: value
        })
        await singleValue.insert();
      }
    }
  }

  async deleteSingleValues(name) {
    // await frappe.db.run('delete from SingleValue where parent=?', name)
  }

  prepareChild(parenttype, parent, child, field, idx) {
    if (!child.name) {
      child.name = frappe.getRandomString();
    }
    child.parent = parent;
    child.parenttype = parenttype;
    child.parentfield = field.fieldname;
    child.idx = idx;
  }

  getKeys(doctype) {
    return frappe.getMeta(doctype).getValidFields({ withChildren: false });
  }

  getFormattedValues(fields, doc) {
    let values = fields.map(field => {
      let value = doc[field.fieldname];
      return this.getFormattedValue(field, value);
    });
    return values;
  }

  getFormattedValue(field, value) {
    if (value instanceof Date) {
      if (field.fieldtype === 'Date') {
        // date
        return value.toISOString().substr(0, 10);
      } else {
        // datetime
        return value.toISOString();
      }
    } else if (field.fieldtype === 'Link' && !value) {
      // empty value must be null to satisfy
      // foreign key constraint
      return null;
    } else {
      return value;
    }
  }

  async deleteMany(doctype, names) {
    for (const name of names) {
      await this.delete(doctype, name);
    }
  }

  async delete(doctype, name) {
    await this.deleteOne(doctype, name);

    // delete children
    let tableFields = frappe.getMeta(doctype).getTableFields();
    for (let field of tableFields) {
      await this.deleteChildren(field.childtype, name);
    }

    this.triggerChange(doctype, name);
  }

  async deleteOne(doctype, name) {
    // delete from {doctype} where name = ?
  }

  async deleteChildren(parenttype, parent) {
    // delete from {parenttype} where parent = ?
  }

  async exists(doctype, name) {
    return (await this.getValue(doctype, name)) ? true : false;
  }

  async getValue(doctype, filters, fieldname = 'name') {
    if (typeof filters === 'string') {
      filters = { name: filters };
    }

    let row = await this.getAll({
      doctype: doctype,
      fields: [fieldname],
      filters: filters,
      start: 0,
      limit: 1,
      orderBy: 'name',
      order: 'asc'
    });
    return row.length ? row[0][fieldname] : null;
  }

  async setValue(doctype, name, fieldname, value) {
    return await this.setValues(doctype, name, {
      [fieldname]: value
    });
  }

  async setValues(doctype, name, fieldValuePair) {
    //
  }

  getAll({ doctype, fields, filters, start, limit, orderBy = 'modified', order = 'desc' } = {}) {
    // select {fields} from {doctype} where {filters} order by {orderBy} {order} limit {start} {limit}
  }

  getFilterConditions(filters) {
    // {"status": "Open"} => `status = "Open"`

    // {"status": "Open", "name": ["like", "apple%"]}
    // => `status="Open" and name like "apple%"

    // {"date": [">=", "2017-09-09", "<=", "2017-11-01"]}
    // => `date >= 2017-09-09 and date <= 2017-11-01`

    let filtersArray = [];

    for (let key in filters) {
      let value = filters[key];
      let field = key;
      let operator = '=';
      let comparisonValue = value;

      if (Array.isArray(value)) {
        operator = value[0];
        comparisonValue = value[1];
        operator = operator.toLowerCase();

        if (operator === 'includes') {
          operator = 'like';
        }

        if (['like', 'includes'].includes(operator) && !comparisonValue.includes('%')) {
          comparisonValue = `%${comparisonValue}%`;
        }
      }

      filtersArray.push([field, operator, comparisonValue]);

      if (Array.isArray(value) && value.length > 2) {
        // multiple conditions
        let operator = value[2];
        let comparisonValue = value[3];
        filtersArray.push([field, operator, comparisonValue]);
      }
    }

    let conditions = filtersArray.map(filter => {
      const [field, operator, comparisonValue] = filter;

      let placeholder = Array.isArray(comparisonValue) ?
        comparisonValue.map(v => '?').join(', ') :
        '?';

      return `ifnull(${field}, '') ${operator} (${placeholder})`;
    });

    let values = filtersArray.reduce((acc, filter) => {
      const comparisonValue = filter[2];
      if (Array.isArray(comparisonValue)) {
        acc = acc.concat(comparisonValue);
      } else {
        acc.push(comparisonValue);
      }
      return acc;
    }, []);

    return {
      conditions: conditions.length ? conditions.join(" and ") : "",
      values
    };
  }

  async run(query, params) {
    // run query
  }

  async sql(query, params) {
    // run sql
  }

  async commit() {
    // commit
  }

  initTypeMap() {
    this.typeMap = {
      'Autocomplete': 'text'
      , 'Currency': 'real'
      , 'Int': 'integer'
      , 'Float': 'real'
      , 'Percent': 'real'
      , 'Check': 'integer'
      , 'Small Text': 'text'
      , 'Long Text': 'text'
      , 'Code': 'text'
      , 'Text Editor': 'text'
      , 'Date': 'text'
      , 'Datetime': 'text'
      , 'Time': 'text'
      , 'Text': 'text'
      , 'Data': 'text'
      , 'Link': 'text'
      , 'DynamicLink': 'text'
      , 'Password': 'text'
      , 'Select': 'text'
      , 'Read Only': 'text'
      , 'File': 'text'
      , 'Attach': 'text'
      , 'Attach Image': 'text'
      , 'Signature': 'text'
      , 'Color': 'text'
      , 'Barcode': 'text'
      , 'Geolocation': 'text'
    }
  }

}