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use eosio::*;
use eosio_cdt::*;

#[derive(Read, Write, NumBytes, Copy, Clone)]
pub struct Account {
    pub balance: Asset,
}

impl Table for Account {
    type Row = Self;

    const NAME: TableName = TableName::new(n!("accounts"));

    fn primary_key(row: &Self::Row) -> u64 {
        row.balance.symbol.code().as_u64()
    }
}

#[derive(Read, Write, NumBytes, Copy, Clone)]
pub struct CurrencyStats {
    pub supply: Asset,
    pub max_supply: Asset,
    pub issuer: AccountName,
}

impl Table for CurrencyStats {
    type Row = Self;

    const NAME: TableName = TableName::new(n!("stat"));

    fn primary_key(row: &Self::Row) -> u64 {
        row.supply.symbol.code().as_u64()
    }
}

#[eosio::action]
fn create(issuer: AccountName, max_supply: Asset) {
    let code = current_receiver();
    require_auth(code);

    let symbol = max_supply.symbol;
    assert!(symbol.is_valid(), "invalid symbol name");
    assert!(max_supply.is_valid(), "invalid supply");
    assert!(max_supply.amount > 0, "max-supply must be positive");

    let symbol_code = symbol.code();
    let stats_table = CurrencyStats::table(code, symbol_code);
    assert!(
        stats_table.find(symbol_code).is_none(),
        "token with symbol already exists",
    );

    let stats = CurrencyStats {
        supply: Asset { amount: 0, symbol },
        max_supply,
        issuer,
    };

    stats_table.emplace(code, stats).expect("write");
}

#[eosio::action]
fn issue(to: AccountName, quantity: Asset, memo: String) {
    let symbol = quantity.symbol;
    assert!(symbol.is_valid(), "invalid symbol name");
    assert!(memo.len() <= 256, "memo has more than 256 bytes");

    let code = current_receiver();
    let symbol_code = symbol.code();
    let stats_table = CurrencyStats::table(code, symbol_code);
    let cursor = stats_table
        .find(symbol_code)
        .expect("token with symbol does not exist, create token before issue");

    let mut st = cursor.get().expect("read");
    assert!(
        to == st.issuer,
        "tokens can only be issued to issuer account",
    );
    require_auth(st.issuer);
    assert!(quantity.is_valid(), "invalid quantity");
    assert!(quantity.amount > 0, "must issue positive quantity");
    assert!(
        quantity.symbol == st.supply.symbol,
        "symbol precision mismatch",
    );
    assert!(
        quantity.amount <= st.max_supply.amount - st.supply.amount,
        "quantity exceeds available supply",
    );

    st.supply += quantity;
    cursor.modify(Payer::Same, st).expect("write");

    add_balance(st.issuer, quantity, st.issuer);

    if to != st.issuer {
        let action = Transfer {
            from: st.issuer,
            to,
            quantity,
            memo,
        };
        send_inline_action(&action.to_action(current_receiver(), vec![
            PermissionLevel {
                actor: st.issuer,
                permission: n!("active").into(),
            },
        ]))
        .expect("failed to send inline action");
    }
}

#[eosio::action]
fn retire(quantity: Asset, memo: String) {
    let symbol = quantity.symbol;
    assert!(symbol.is_valid(), "invalid symbol name");
    assert!(memo.len() <= 256, "memo has more than 256 bytes");

    let code = current_receiver();
    let symbol_code = symbol.code();
    let stats_table = CurrencyStats::table(code, symbol_code);
    let cursor = stats_table
        .find(symbol_code)
        .expect("token with symbol does not exist");

    let mut st = cursor.get().expect("error reading stats table");
    require_auth(st.issuer);
    assert!(quantity.is_valid(), "invalid quantity");
    assert!(quantity.amount > 0, "must retire positive quantity");
    assert!(symbol == st.supply.symbol, "symbol precision mismatch");

    st.supply -= quantity;
    cursor.modify(Payer::Same, st).expect("write");
    sub_balance(st.issuer, quantity);
}

#[eosio::action]
fn transfer(from: AccountName, to: AccountName, quantity: Asset, memo: String) {
    assert!(from != to, "cannot transfer to self");
    require_auth(from);
    assert!(is_account(to), "to account does not exist");

    let code = current_receiver();
    let symbol_code = quantity.symbol.code();
    let stats_table = CurrencyStats::table(code, symbol_code);
    let cursor = stats_table
        .find(symbol_code)
        .expect("token with symbol does not exist");
    let st = cursor.get().expect("read");

    require_recipient(from);
    require_recipient(to);

    assert!(quantity.is_valid(), "invalid quantity");
    assert!(quantity.amount > 0, "must transfer positive quantity");
    assert!(
        quantity.symbol == st.supply.symbol,
        "symbol precision mismatch",
    );
    assert!(memo.len() <= 256, "memo has more than 256 bytes");

    let payer = if has_auth(to) { to } else { from };

    sub_balance(from, quantity);
    add_balance(to, quantity, payer);
}

fn sub_balance(owner: AccountName, value: Asset) {
    let code = current_receiver();
    let table = Account::table(code, owner);
    let cursor = table
        .find(value.symbol.code())
        .expect("no balance object found");
    let mut from = cursor.get().expect("read");
    assert!(from.balance.amount >= value.amount, "overdrawn balance");

    from.balance -= value;
    cursor.modify(Payer::Same, from).expect("write");
}

fn add_balance(owner: AccountName, value: Asset, ram_payer: AccountName) {
    let code = current_receiver();
    let accounts_table = Account::table(code, owner);
    let cursor = accounts_table.find(value.symbol.code());
    match cursor {
        Some(cursor) => {
            let mut account = cursor.get().expect("read");
            account.balance += value;
            cursor
                .modify(Payer::New(ram_payer), &account)
                .expect("write");
        }
        None => {
            let account = Account { balance: value };
            accounts_table.emplace(ram_payer, &account).expect("write");
        }
    }
}

#[eosio::action]
fn open(owner: AccountName, symbol: Symbol, ram_payer: AccountName) {
    require_auth(ram_payer);
    assert!(is_account(owner), "owner account does not exist");

    let code = current_receiver();
    let symbol_code = symbol.code();

    let stats_table = CurrencyStats::table(code, symbol_code);
    let st = stats_table
        .find(symbol_code)
        .expect("symbol does not exist")
        .get()
        .expect("read");
    assert!(st.supply.symbol == symbol, "symbol precision mismatch");

    let accts_table = Account::table(code, owner);
    if accts_table.find(symbol_code).is_none() {
        let account = Account {
            balance: Asset { amount: 0, symbol },
        };
        accts_table.emplace(ram_payer, account).expect("write");
    }
}

#[eosio::action]
fn close(owner: AccountName, symbol: Symbol) {
    require_auth(owner);
    let code = current_receiver();
    let accts_table = Account::table(code, owner);
    let accts_cursor = accts_table.find(symbol.code()).expect(
        "Balance row already deleted or never existed. Action won't have any \
         effect.",
    );
    let account = accts_cursor.get().expect("read");
    assert!(
        account.balance.amount == 0,
        "Cannot close because the balance is not zero.",
    );
    accts_cursor.erase().expect("read");
}

eosio::abi!(create, issue, transfer, open, close, retire);