# FrugalityBot
# Copyright (C) 2026 Eri (csxkdv/nxkdv) nxkdv@thenight.club
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

require 'pg'

class Database
    def initialize
        # Connect once when the bot starts
        @conn = PG.connect(
            host: ENV['DB_HOST'] || 'localhost',
            dbname: ENV['DB_NAME'] || 'fgbot_db',
            user: ENV['DB_USER'] || 'postgres'
        )

        init_tables
    end

    def init_tables
        sql_wallet = <<~SQL
        CREATE TABLE IF NOT EXISTS wallets (
            user_id BIGINT PRIMARY KEY,
            amount BIGINT DEFAULT 0
        );
        SQL

        sql_ledger = <<~SQL
        CREATE TABLE IF NOT EXISTS transactions (
            id SERIAL PRIMARY KEY,
            user_id BIGINT NOT NULL,
            amount BIGINT NOT NULL,
            reason VARCHAR(50),
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        );
        SQL

        sql_index = <<~SQL
        CREATE INDEX IF NOT EXISTS idx_user_history 
        ON transactions(user_id, created_at);
        SQL

        @conn.exec(sql_wallet)
        @conn.exec(sql_ledger)
        @conn.exec(sql_index)

        begin
            @conn.exec("ALTER TABLE wallets ADD COLUMN IF NOT EXISTS locale VARCHAR(5) DEFAULT 'en'")
        rescue PG::Error => e
            puts "Migration note: #{e.message}"
        end

        puts "Database tables have been initialized."
    end

    def get_currency(user_id)
        # Run the query using parameters ($1) to prevent SQL injection
        result = @conn.exec_params("SELECT amount FROM wallets WHERE user_id = $1", [user_id])

        if result.num_tuples.zero?
            return 0 # User has no money/row yet
        else
            return result[0]['amount'].to_i
        end
    end

    def update_balance(user_id, amount, reason = "transaction")
        @conn.transaction do
            @conn.exec_params(
                "INSERT INTO transactions (user_id, amount, reason) VALUES ($1, $2, $3)",
                [user_id, amount, reason]
            )
            
            # We update the user's wallet
            sql_update = <<~SQL
            INSERT INTO wallets (user_id, amount)
            VALUES ($1, $2)
            ON CONFLICT (user_id)
            DO UPDATE SET amount = wallets.amount + $2
            SQL

            @conn.exec_params(sql_update, [user_id, amount])
        end
    end

    def fetch_report(user_id, interval_string)
        sql = <<~SQL
        SELECT
            SUM(CASE WHEN amount > 0 THEN amount ELSE 0 END) as income,
            SUM(CASE WHEN amount < 0 THEN amount ELSE 0 END) as expenses,
            SUM(amount) AS net_change
        FROM transactions
        WHERE user_id = $1
        AND created_at >= NOW() - $2::INTERVAL
        SQL

        result = @conn.exec_params(sql, [user_id, interval_string])
        row = result[0]

        {
            income: row['income'].to_i,
            expenses: row['expenses'].to_i,
            net: row['net_change'].to_i
        }
    end

    def get_language(user_id)
        result = @conn.exec("SELECT locale FROM wallets WHERE user_id = $1", [user_id])

        return nil if result.num_tuples.zero?

        return result[0]['locale']
    end

    def set_language(user_id, locale)
        sql = <<~SQL
            INSERT INTO wallets(user_id, amount, locale)
            VALUES ($1, 0, $2)
            ON CONFLICT (user_id)
            DO UPDATE SET locale = $2
        SQL

        @conn.exec(sql, [user_id, locale])
    end
end