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

#
# SQL class for Diary Management Application
#

class SQL_Cache < Hash
    def initialize(sql, table, string_expr)
        @sql = sql
        @name = table
        @string_expr = string_expr
        @lists = Hash.new
        @fields = @sql.columns(@name).collect { |col| col["name"] }
        super(0)
    end

    attr_reader :sql, :name
    attr_accessor :string_expr

    def search(where)
        list = Array.new
        @sql.select_all("select * from #{@name} where #{where} order by id") do |row|
            self[row["id"]] = row.to_h
            list.push(self[row["id"]])
        end
        list
    end
    private :search

    def list(where)
        if not @lists[where]
            @lists[where] = search(where).collect do |entry|
                string = @string_expr.dup
                entry.each do |field, value|
                    string.gsub!(/#\{#{field}\}/, value.to_s) if value
                end
                [entry["id"].to_s, string]
            end
        end
        @lists[where]
    end

    def [](id)
        id = id.to_i
        if super(id) == 0
            if search("id = #{id}").length != 1
                self[id] = nil
            end
        end
        super(id)
    end

    def create(data)
        fields = data.keys & @fields
        @sql.do("insert into #{@name} (" +
                fields.join(", ") +
                ") values (" + fields.collect do "?" end.join(", ") +
                ")",
                *(fields.collect do |field| data[field] end))
        @sql.select_one("select last_insert_id()")[0]
    end

    def modify(id, data)
        fields = (@fields & self[id].keys) - ["id"]
        changes = fields.inject([]) do |ch, field|
            if data.has_key?(field) and data[field] != self[id][field]
                ch.push(field)
            else
                ch
            end
        end
        @sql.do("update #{@name} set " +
            changes.collect do |field|
                field + " = ?"
            end.join(", ") + " where id = #{id}",
            *(changes.collect do |field| data[field] end)
        ) if changes.length > 0
    end

    def delete(id)
        @sql.do("delete from #{@name} where id = #{id}")
        super(id)
    end
end