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

/************************************************************************
 * Holder : table commune à tous les titulaires
 * bigint : entier sur 64 bits
 * primary key : clé primaire, identification unique de l'enregistrement
 * generated always as identity : numéro incrément automatique 1, 2, 3 ...
 * Le type est forcé aux 3 valeurs de l'énumération holder_type
 * current_timestamp date et heure courante. Version moderne de now()
 ************************************************************************/
create type holder_type as enum ('BANK', 'PERSON', 'COMPANY');

create table holder (
  "id" bigint primary key generated always as identity,          
  "type" holder_type not null,
  "created_at" timestamp not null default current_timestamp
);

/************************************************************************
 * Bank
 * Liée par références à titulaire (holder) pas d'incrément automatique
 * puisque c'est celui de titulaire
 ************************************************************************/
create table bank (
  "id" bigint primary key references holder(id),
  "name" text not null
);

/************************************************************************
 * Person
 * Liée par références à titulaire (holder) pas d'incrément automatique
 * on delete cascade : Lors de la suppression du titualaire, person est
 * supprimé aussi. Sans cela la suppression est interdite.
 ************************************************************************/
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 check (birthdate <= current_date - interval '15 years')
);

/************************************************************************
 * 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
);

/************************************************************************
 * Company
 * 
 ************************************************************************/
create table currency (
  "code" text primary key
);

/************************************************************************
 * Exchange Rate
 * La clé primaire est sur les deux colonnes currency_code et date
 * Il n'y a qu'un seul taux de change par monnaie ET par jour
 ************************************************************************/
create table exchange_rate (
  "currency_code" text references currency(code) on delete cascade,
  "date" date ,
  "rate" decimal not null,
  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,
  "currency_code" text not null 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) not null 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 not null default current_timestamp,
  amount decimal not null check (amount > 0)
);

create table operation (
  "id" bigint primary key generated always as identity,
  "transaction_id" bigint not null references transaction(id),
  "account_id" bigint not null references account(id),
  amount decimal not null check (amount > 0),
  direction text not null check (direction in ('DEBIT', 'CREDIT'))
);