drop schema if exists bank cascade;
create schema bank;
set search_path TO bank;

/*
 * Holder : table commune à tous les titulaires
 */
create type holder_type as enum ('BANK', 'PERSON', 'COMPANY');

create table holder (
  "id" bigint primary key generated always as identity,          -- identifiant unique
  "type" holder_type  not null,
  "created_at" timestamp not null default current_timestamp      -- date et heure de création
);

/*
 * Bank
 */
create table bank (
  "id" bigint primary key references holder(id),          -- identifiant unique
  "name" text not null                 
);

/*
 * Person
 */
create table person (
  "id" bigint primary key references holder(id) on delete cascade,
  "firstname" text not null,
  "lastname" text not null,
  "birthdate" date not null
);

/*
 * Company
 */
create table company (
  "id" bigint primary key references holder(id) on delete cascade,
  "name" text not null,
  "registration_number" text unique not null,
  "created_at" date not null
);

create table currency (
  "code" text primary key
);

create table exchange_rate (
  "currency_code" text references currency(code) on delete cascade,
  "date" date,
  "rate" decimal,
  primary key (currency_code, date)
);
/*
 * Account
 * La contrainte check (balance >= 0) empêche les soldes négatifs
 */
create table account (
  "id" bigint primary key generated always as identity,
  "opened_at" date not null default current_date,
  "balance" numeric(18,6) not null default 0 check (balance >= 0),
  "currency_code" text references currency (code)
);

/*
 * Account -> Holder
 * Cette table établit la relation n–n entre account et holder.
 * Un compte joint correspond donc à plusieurs lignes dans cette table.
 * La contrainte share assure que les parts sont comprises entre 0 et 1.
 */
create table account_holder (
  "account_id" int not null references account(id) on delete cascade,
  "holder_id" int not null references holder(id) on delete cascade,
  "share" decimal(4,3) default 1 check (share > 0 and share <= 1),
  primary key (account_id, holder_id)
);




create table transaction (
  "id" bigint primary key generated always as identity,
  "transaction_date" timestamp default current_timestamp,
  amount decimal check (amount > 0)
);

create table operation (
  "id" bigint primary key generated always as identity,
  "transaction_id" bigint references transaction(id),
  "account_id" bigint references account(id),
  amount decimal check (amount > 0),
  direction text check (direction in ('DEBIT', 'CREDIT'))
);