# SPDX-License-Identifier: Apache-2.0
# Copyright (C) 2021-2022 OKTET Labs Ltd. All rights reserved.

#
# Class DataMapper for Diary Management Application.
#

require 'mysql2'

class DataMapper
    @@mapper = Hash.new
    @@database = nil

    def initialize(table, key = "id")
        @key = key
        @table = table
        @@mapper[@table] = self
        @cache = Hash.new
        @columns = @@database.query("select column_name from information_schema.columns where table_name='%s'" % @table).collect{ |col| col["column_name"] } - [@key]
    end
    def self.setup(args)
        raise "Database parameters is not a hash" unless args.is_a? Hash
        @@database = Mysql2::Client.new(:host => args[:host], :username => args[:username], :password => args[:password], :database => args[:database])
    end
    def self.database
        @@database
    end

    def pick(row)
        row_data = row.to_h
        id = row_data[@key]
        return @cache[id] if @cache.has_key?(id)
        @cache[id] = instantiate(id, row_data)
    end

    def find(id)
        return @cache[id] if @cache.has_key?(id)
        row = @@database.query("select * from #{@table} where #{@key} = '%s' LIMIT 1" % id).first
        return nil unless row
        pick(row)
    end

    def where(clause, *args)
        cmd = "select * from #{@table} where " + clause % args
        @@database.query(cmd).collect { |row| pick(row) }
    end

    def all(args)
        # TODO: args == nil
        raise ArgumentError unless args.is_a?(Hash)
        query_clause = Array.new
        query_args = Array.new
        args.each do |tag, value|
            next unless @columns.include?(tag.to_s) or tag.to_s == @key
            if value.is_a?(Array)
                if value.length > 0
                    query_clause << "#{tag.to_s} " +
                                    "IN (#{value.collect {"'%s'"}.join(",")})"
                    query_args = query_args + value
                end
            elsif value.is_a?(Range)
                query_clause << "#{tag.to_s} >= '%s' AND #{tag.to_s} <= '%s'"
                query_args << value.first << value.last
            else
                query_clause << "#{tag.to_s} = '%s'"
                query_args << value
            end
        end
#        raise "#{MyCGI.dump(query_clause)} : #{MyCGI.dump(query_args)}"
        cmd = "select * from #{@table}" + (query_clause.empty? ? "" :  " where " + query_clause.join(" and ")) % query_args
        @@database.query(cmd).collect { |row| pick(row) }
    end

    def insert(obj)
        raise ArgumentError unless obj.id.nil?
        fields = @columns & obj.attributes.keys
        @@database.do("insert into #{@table} (" + fields.join(",") +
                      ") values (" + fields.collect {"?"}.join(",") + ")",
                      *(fields.collect {|field| obj[field]}))
        obj.id = @@database.query("select last_insert_id() as id").first["id"]
        @@cache[obj.id] = obj
    end

    def update(obj)
        raise ArgumentError if obj.id.nil?
        fields = @columns & obj.attributes.keys
        @@database.do("update #{@table} set " +
                      fields.collect {|field| field + " = ?"}.join(",") +
                      " where #{@key} = ?",
                      *(fields.collect {|field| obj[field]} << obj.id))
    end

    def delete(obj)
        raise ArgumentError if obj.id.nil?
        @@database.do("delete from #{@table} where #{@key} = ?", obj.id)
        @@cache.delete(obj.id)
        obj.id = nil
    end

    def self.[](table)
        @@mapper[table]
    end
end