db: finish sql commands

README.md

@@ -421,27 +421,28 @@ The following basic use cases are to be implemented at the first time.
 
 - [X] A user signs up
 - [X] A user logs in
-- [X] A user lists their events (pagination)
+- [ ] A user lists their events (pagination)
-- [X] A user sees the detail of an event (description, members, amount)
+- [ ] A user sees the detail of an event (description, members, amount)
-- [] A user sees the expenses of an event (total amount, personal expenses, pagination)
+- [ ] A user sees the expenses of an event (total amount, personal expenses, pagination)
-- [] A user sees the detail of an expense: (time, amount, payers, recipients)
+- [ ] A user sees the detail of an expense: (time, amount, payers, recipients)
-- [] A user adds an expense
+- [ ] A user adds an expense
-- [] A user updates/changes an expense (may handle some extra access control)
+- [ ] A user updates/changes an expense (may handle some extra access control)
-- [] A user deletes an expense (may handle some extra access control)
+- [ ] A user can pay the debt to other members (just a special case of expense)
-- [] A user restore a deleted expense
+- [ ] A user creates an event (and participate to it)
-- [] A user can pay the debt to other members
+- [ ] A user updates the event info
-- [X] A user creates an event (and participate to it)
+- [ ] A user invites another user by sending a mail with a token.
-- [X] A user updates the event info
+- [ ] A user joins an event by accepting an invitation
-- [X] A user invites another user by sending a mail with a token.
+- [ ] A user cannot see other user's information
-- [X] A user joins an event by accepting an invitation
+- [ ] A user cannot see the events that they didn't participated in.
-- [] ~A user quits an event (they cannot actually, but we can make as if they quitted)~ 
-**No we can't quit!**
-- [] A user cannot see other user's information
-- [] A user cannot see the events that they didn't participated in.
 
 For the second stage:
 
-- [] A user can archive an event
+- [ ] A user can archive an event
+- [ ] A user deletes an expense (may handle some extra access control)
+- [ ] A user restore a deleted expense
+- [ ] Audit log for expense updates/deletes
+- [ ] ~A user quits an event (they cannot actually, but we can make as if they
+quitted)~ **No we can't quit!**
 
 With those functionalities, there will be an usable product. And then we can
 work on other aspects. For example:
@@ -491,3 +492,30 @@ GROUP BY
     o.id, o.first_name, o.last_name;
 
 ```
+
+### 2024/10/19
+
+I don't plan to handle deletions at this first stage, but I note down what I
+have thought of.
+
+1. Just delete. But keep a replica at the front end of the object that we are
+deleting. And propose an option to restore (so a new record is added to the DB)
+2. Just delete, but wait. The request is sent to a queue with a timeout of
+several seconds, if the user regrets, they can cancel the request. This can be
+done on the front, but also on the back. I think it is better to do in on the
+front-end.
+3. Never deletes. But keep a state in the DB `deleted`. They will just be
+ignored when counting.
+4. Deletes when doing database cleanup. They lines deleted will be processed
+when we cleanup the DB. And they will be definitely deleted at that time.
+
+I can create a audit log table to log all the critical
+changes in my `expense` table (update or delete).
+
+Finished with the basic SQL commands. Learned a lot from SQL about `JOIN`,
+aggregation and `CTE`. SQL itself has quite amount of things to learn, this
+is on my future learning plan!
+
+_I found it quite interesting that simply with SQL, we can simulate the most
+business logic. It is a must-have competence for software design and
+development._

internal/howmuch/adapter/repo/sqlc/expense.sql

@@ -0,0 +1,72 @@
+-- name: InsertExpense :one
+INSERT INTO "expense" (
+    created_at, updated_at, amount, currency, event_id, name, place
+) VALUES ( $1, $2, $3, $4, $5, $6, $7 )
+RETURNING *;
+
+-- name: DeleteExpense :exec
+DELETE FROM "expense" WHERE id = $1;
+
+-- name: DeleteTransactionsOfExpenseID :exec
+DELETE FROM "transaction" WHERE transaction.expense_id = $1;
+
+-- name: UpdateExpenseByID :one
+UPDATE "expense"
+SET updated_at = $2, amount = $3, currency = $4, name = $5, place = $6
+WHERE id = $1
+RETURNING *;
+
+-- name: ListExpensesByEventID :many
+SELECT
+    ex.id, ex.created_at, ex.updated_at, ex.amount, ex.currency, ex.event_id,
+    ex.name, ex.place
+FROM "expense" ex
+JOIN "event" ev ON ev.id = ex.event_id
+WHERE ev.id = $1;
+
+-- name: ListExpensesByEventIDByUserID :many
+SELECT
+    ex.id, ex.created_at, ex.updated_at, ex.amount, ex.currency, ex.event_id,
+    ex.name, ex.place
+FROM "expense" ex
+JOIN "event" ev ON ev.id = ex.event_id
+WHERE ev.id = $1;
+
+-- name: GetExpenseByID :one
+WITH payer_transaction as (
+    SELECT pt.expense_id,
+        json_agg(json_build_object(
+            'payer_id', p.id,
+            'payer_first_name', p.first_name,
+            'payer_last_name', p.last_name,
+            'amount', pt.amount,
+            'currency', pt.currency
+        )) AS payments
+    FROM "transaction" pt
+    JOIN "user" p ON p.id = pt.user_id
+    WHERE pt.is_income = FALSE
+    GROUP BY pt.expense_id
+), -- For each expense, aggregate payment info
+recipient_transaction as (
+    SELECT rt.expense_id,
+        json_agg(json_build_object(
+            'recipient_id', p.id,
+            'recipient_first_name', p.first_name,
+            'recipient_last_name', p.last_name,
+            'amount', rt.amount,
+            'currency', rt.currency
+        )) AS benefits
+    FROM "transaction" rt
+    JOIN "user" p ON p.id = rt.user_id
+    WHERE rt.is_income = TRUE
+    GROUP BY rt.expense_id
+) -- For each expense, aggregate benefits info
+SELECT
+    ex.id, ex.created_at, ex.updated_at, ex.amount, ex.currency, ex.event_id,
+    ex.name, ex.place,
+    COALESCE(pt.payments, '[]') AS payments,
+    COALESCE(rt.benefits, '[]') AS benefits
+FROM "expense" ex
+LEFT JOIN "payer_transaction" pt ON pt.expense_id = ex.id
+LEFT JOIN "recipient_transaction" rt ON rt.expense_id = ex.id
+WHERE ex.id = $1;

internal/howmuch/adapter/repo/sqlc/expense.sql.go

@@ -0,0 +1,264 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.27.0
+// source: expense.sql
+
+package sqlc
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"time"
+)
+
+const deleteExpense = `-- name: DeleteExpense :exec
+DELETE FROM "expense" WHERE id = $1
+`
+
+func (q *Queries) DeleteExpense(ctx context.Context, id int32) error {
+	_, err := q.db.ExecContext(ctx, deleteExpense, id)
+	return err
+}
+
+const deleteTransactionsOfExpenseID = `-- name: DeleteTransactionsOfExpenseID :exec
+DELETE FROM "transaction" WHERE transaction.expense_id = $1
+`
+
+func (q *Queries) DeleteTransactionsOfExpenseID(ctx context.Context, expenseID int32) error {
+	_, err := q.db.ExecContext(ctx, deleteTransactionsOfExpenseID, expenseID)
+	return err
+}
+
+const getExpenseByID = `-- name: GetExpenseByID :one
+WITH payer_transaction as (
+    SELECT pt.expense_id,
+        json_agg(json_build_object(
+            'payer_id', p.id,
+            'payer_first_name', p.first_name,
+            'payer_last_name', p.last_name,
+            'amount', pt.amount,
+            'currency', pt.currency
+        )) AS payments
+    FROM "transaction" pt
+    JOIN "user" p ON p.id = pt.user_id
+    WHERE pt.is_income = FALSE
+    GROUP BY pt.expense_id
+), -- For each expense, aggregate payment info
+recipient_transaction as (
+    SELECT rt.expense_id,
+        json_agg(json_build_object(
+            'recipient_id', p.id,
+            'recipient_first_name', p.first_name,
+            'recipient_last_name', p.last_name,
+            'amount', rt.amount,
+            'currency', rt.currency
+        )) AS benefits
+    FROM "transaction" rt
+    JOIN "user" p ON p.id = rt.user_id
+    WHERE rt.is_income = TRUE
+    GROUP BY rt.expense_id
+) -- For each expense, aggregate benefits info
+SELECT
+    ex.id, ex.created_at, ex.updated_at, ex.amount, ex.currency, ex.event_id,
+    ex.name, ex.place,
+    COALESCE(pt.payments, '[]') AS payments,
+    COALESCE(rt.benefits, '[]') AS benefits
+FROM "expense" ex
+LEFT JOIN "payer_transaction" pt ON pt.expense_id = ex.id
+LEFT JOIN "recipient_transaction" rt ON rt.expense_id = ex.id
+WHERE ex.id = $1
+`
+
+type GetExpenseByIDRow struct {
+	ID        int32
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	Amount    int32
+	Currency  string
+	EventID   int32
+	Name      sql.NullString
+	Place     sql.NullString
+	Payments  json.RawMessage
+	Benefits  json.RawMessage
+}
+
+func (q *Queries) GetExpenseByID(ctx context.Context, id int32) (GetExpenseByIDRow, error) {
+	row := q.db.QueryRowContext(ctx, getExpenseByID, id)
+	var i GetExpenseByIDRow
+	err := row.Scan(
+		&i.ID,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+		&i.Amount,
+		&i.Currency,
+		&i.EventID,
+		&i.Name,
+		&i.Place,
+		&i.Payments,
+		&i.Benefits,
+	)
+	return i, err
+}
+
+const insertExpense = `-- name: InsertExpense :one
+INSERT INTO "expense" (
+    created_at, updated_at, amount, currency, event_id, name, place
+) VALUES ( $1, $2, $3, $4, $5, $6, $7 )
+RETURNING id, created_at, updated_at, amount, currency, event_id, name, place
+`
+
+type InsertExpenseParams struct {
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	Amount    int32
+	Currency  string
+	EventID   int32
+	Name      sql.NullString
+	Place     sql.NullString
+}
+
+func (q *Queries) InsertExpense(ctx context.Context, arg InsertExpenseParams) (Expense, error) {
+	row := q.db.QueryRowContext(ctx, insertExpense,
+		arg.CreatedAt,
+		arg.UpdatedAt,
+		arg.Amount,
+		arg.Currency,
+		arg.EventID,
+		arg.Name,
+		arg.Place,
+	)
+	var i Expense
+	err := row.Scan(
+		&i.ID,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+		&i.Amount,
+		&i.Currency,
+		&i.EventID,
+		&i.Name,
+		&i.Place,
+	)
+	return i, err
+}
+
+const listExpensesByEventID = `-- name: ListExpensesByEventID :many
+SELECT
+    ex.id, ex.created_at, ex.updated_at, ex.amount, ex.currency, ex.event_id,
+    ex.name, ex.place
+FROM "expense" ex
+JOIN "event" ev ON ev.id = ex.event_id
+WHERE ev.id = $1
+`
+
+func (q *Queries) ListExpensesByEventID(ctx context.Context, id int32) ([]Expense, error) {
+	rows, err := q.db.QueryContext(ctx, listExpensesByEventID, id)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Expense
+	for rows.Next() {
+		var i Expense
+		if err := rows.Scan(
+			&i.ID,
+			&i.CreatedAt,
+			&i.UpdatedAt,
+			&i.Amount,
+			&i.Currency,
+			&i.EventID,
+			&i.Name,
+			&i.Place,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listExpensesByEventIDByUserID = `-- name: ListExpensesByEventIDByUserID :many
+SELECT
+    ex.id, ex.created_at, ex.updated_at, ex.amount, ex.currency, ex.event_id,
+    ex.name, ex.place
+FROM "expense" ex
+JOIN "event" ev ON ev.id = ex.event_id
+WHERE ev.id = $1
+`
+
+func (q *Queries) ListExpensesByEventIDByUserID(ctx context.Context, id int32) ([]Expense, error) {
+	rows, err := q.db.QueryContext(ctx, listExpensesByEventIDByUserID, id)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Expense
+	for rows.Next() {
+		var i Expense
+		if err := rows.Scan(
+			&i.ID,
+			&i.CreatedAt,
+			&i.UpdatedAt,
+			&i.Amount,
+			&i.Currency,
+			&i.EventID,
+			&i.Name,
+			&i.Place,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const updateExpenseByID = `-- name: UpdateExpenseByID :one
+UPDATE "expense"
+SET updated_at = $2, amount = $3, currency = $4, name = $5, place = $6
+WHERE id = $1
+RETURNING id, created_at, updated_at, amount, currency, event_id, name, place
+`
+
+type UpdateExpenseByIDParams struct {
+	ID        int32
+	UpdatedAt time.Time
+	Amount    int32
+	Currency  string
+	Name      sql.NullString
+	Place     sql.NullString
+}
+
+func (q *Queries) UpdateExpenseByID(ctx context.Context, arg UpdateExpenseByIDParams) (Expense, error) {
+	row := q.db.QueryRowContext(ctx, updateExpenseByID,
+		arg.ID,
+		arg.UpdatedAt,
+		arg.Amount,
+		arg.Currency,
+		arg.Name,
+		arg.Place,
+	)
+	var i Expense
+	err := row.Scan(
+		&i.ID,
+		&i.CreatedAt,
+		&i.UpdatedAt,
+		&i.Amount,
+		&i.Currency,
+		&i.EventID,
+		&i.Name,
+		&i.Place,
+	)
+	return i, err
+}

internal/howmuch/adapter/repo/sqlc/models.go

@@ -27,6 +27,17 @@ type Event struct {
 	TotalAmount     sql.NullInt32
 }
 
+type Expense struct {
+	ID        int32
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	Amount    int32
+	Currency  string
+	EventID   int32
+	Name      sql.NullString
+	Place     sql.NullString
+}
+
 type Participation struct {
 	ID              int32
 	UserID          int32
@@ -36,6 +47,17 @@ type Participation struct {
 	UpdatedAt       time.Time
 }
 
+type Transaction struct {
+	ID        int32
+	ExpenseID int32
+	UserID    int32
+	Amount    int32
+	Currency  string
+	IsIncome  bool
+	CreatedAt time.Time
+	UpdatedAt time.Time
+}
+
 type User struct {
 	ID        int32
 	Email     string

internal/howmuch/adapter/repo/sqlc/transaction.sql

@@ -0,0 +1,5 @@
+-- name: InsertTransaction :exec
+INSERT INTO "transaction" (
+    created_at, updated_at, amount, currency, expense_id, user_id, is_income
+) VALUES ( $1, $2, $3, $4, $5, $6, $7 )
+RETURNING *;

internal/howmuch/adapter/repo/sqlc/transaction.sql.go

@@ -0,0 +1,41 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.27.0
+// source: transaction.sql
+
+package sqlc
+
+import (
+	"context"
+	"time"
+)
+
+const insertTransaction = `-- name: InsertTransaction :exec
+INSERT INTO "transaction" (
+    created_at, updated_at, amount, currency, expense_id, user_id, is_income
+) VALUES ( $1, $2, $3, $4, $5, $6, $7 )
+RETURNING id, expense_id, user_id, amount, currency, is_income, created_at, updated_at
+`
+
+type InsertTransactionParams struct {
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	Amount    int32
+	Currency  string
+	ExpenseID int32
+	UserID    int32
+	IsIncome  bool
+}
+
+func (q *Queries) InsertTransaction(ctx context.Context, arg InsertTransactionParams) error {
+	_, err := q.db.ExecContext(ctx, insertTransaction,
+		arg.CreatedAt,
+		arg.UpdatedAt,
+		arg.Amount,
+		arg.Currency,
+		arg.ExpenseID,
+		arg.UserID,
+		arg.IsIncome,
+	)
+	return err
+}

internal/howmuch/model/expense.go

@@ -24,16 +24,44 @@ package model
 
 import "time"
 
+// {{{ Requrest
+
 type ExpenseRequest struct {
-	Amount       Money         `json:"money"         binding:"required,number"`
+	Amount   Money         `json:"money"    binding:"required"`
-	PayerIDs     []int         `json:"payer_ids"     binding:"required"`
+	Payments []Payment     `json:"payments" binding:"required"`
-	RecipientIDs []int         `json:"recipient_ids" binding:"required"`
+	Benefits []Benefit     `json:"benefits" binding:"required"`
 	EventID  int           `json:"event_id" binding:"required"`
 	Detail   ExpenseDetail `json:"detail"`
 }
 
+// }}}
+// {{{ Response
+
+type ExpensesListResponse struct {
+	ID        int       `json:"id"`
+	CreatedAt time.Time `json:"created_at"`
+	UpdatedAt time.Time `json:"updated_at"`
+
+	Amount  Money `json:"money"`
+	EventID int   `json:"event_id"`
+
+	Detail ExpenseDetail `json:"detail"`
+}
+
+type ExpenseGetResponse Expense
+
+// }}}
+// {{{ Retrieved
+
+type ExpensesListRetrieved ExpensesListResponse
+
+// }}}
+// {{{ Entity
+
 type ExpenseEntity struct {
 	ID        int
+	CreatedAt time.Time
+	UpdatedAt time.Time
 
 	Amount   int
 	Currency string
@@ -42,30 +70,42 @@ type ExpenseEntity struct {
 	// ExpenseDetail
 	Name  string
 	Place string
-
-	CreatedAt time.Time
-	UpdatedAt time.Time
 }
 
+// }}}
+// {{{ Domain Models
+
 type ExpenseDetail struct {
 	Name  string `json:"name"`
 	Place string `json:"place"`
 }
 
-type Expense struct {
+type Payment struct {
-	ID int
+	PayerID        int    `json:"payer_id"         binding:"required,number"`
-
+	PayerFirstName string `json:"payer_first_name"`
-	Amount Money
+	PayerLastName  string `json:"payer_last_name"`
-
+	Amount         Money  `json:"amount"           binding:"required"`
-	// Lazy aggregate using Transaction join
-	PayerIDs []int
-
-	// Lazy aggregate using Transaction join
-	RecipientIDs []int
-
-	EventID int
-	Detail  ExpenseDetail
-
-	CreatedAt time.Time
-	UpdatedAt time.Time
 }
+
+type Benefit struct {
+	RecipientID        int    `json:"recipient_id"         binding:"required,number"`
+	RecipientFirstName string `json:"recipient_first_name"`
+	RecipientLastName  string `json:"recipient_last_name"`
+	Amount             Money  `json:"amount"               binding:"required"`
+}
+
+type Expense struct {
+	ID        int       `json:"id"`
+	CreatedAt time.Time `json:"created_at"`
+	UpdatedAt time.Time `json:"updated_at"`
+
+	Amount  Money `json:"money"`
+	EventID int   `json:"event_id"`
+
+	Detail ExpenseDetail `json:"detail"`
+
+	Payments []Payment `json:"payments"`
+	Benefits []Benefit `json:"benefits"`
+}
+
+// }}}

internal/howmuch/model/transaction.go

@@ -24,18 +24,25 @@ package model
 
 import "time"
 
+// {{{ Entity
+
 type TransactionEntity Transaction
 
-// Transaction is the association between Expenses and Users
+// }}}
+// {{{ Domain object
+
 type Transaction struct {
 	ID int
 
-	ExpenseID Expense
+	ExpenseID int
 	UserID    int
 	Amount    int
 	Currency  string
-	IsIncome  bool
+	IsIncome  bool // To note that the direction of the money (payment or income)
 
 	CreatedAt time.Time
 	UpdatedAt time.Time
 }
+
+// }}}
+// Transaction is the association between Expenses and Users

migrations/20241019110734_create_transaction_table.postgres.down.sql

@@ -0,0 +1 @@
+

migrations/20241019110734_create_transaction_table.postgres.up.sql

@@ -0,0 +1,14 @@
+CREATE TABLE "transaction" (
+  "id" serial NOT NULL,
+  PRIMARY KEY ("id"),
+  "expense_id" integer NOT NULL,
+  "user_id" integer NOT NULL,
+  "amount" integer NOT NULL,
+  "currency" character varying(255) NOT NULL,
+  "is_income" boolean NOT NULL DEFAULT FALSE,
+  "created_at" date NOT NULL,
+  "updated_at" date NOT NULL
+);
+
+ALTER TABLE "transaction"
+ADD FOREIGN KEY ("user_id") REFERENCES "user" ("id") ON DELETE CASCADE ON UPDATE CASCADE;

migrations/20241019112255_create_expense_table.postgres.down.sql

@@ -0,0 +1 @@
+DROP TABLE "expense";

migrations/20241019112255_create_expense_table.postgres.up.sql

@@ -0,0 +1,14 @@
+CREATE TABLE "expense" (
+  "id" serial NOT NULL,
+  PRIMARY KEY ("id"),
+  "created_at" date NOT NULL,
+  "updated_at" date NOT NULL,
+  "amount" integer NOT NULL,
+  "currency" character varying NOT NULL,
+  "event_id" integer NOT NULL,
+  "name" character varying(255) NULL,
+  "place" character varying(1000) NULL
+);
+
+ALTER TABLE "expense"
+ADD FOREIGN KEY ("event_id") REFERENCES "event" ("id") ON DELETE CASCADE ON UPDATE CASCADE

migrations/20241019112421_fk_transaction_expense.postgres.down.sql

@@ -0,0 +1 @@
+DROP TABLE transaction;

migrations/20241019112421_fk_transaction_expense.postgres.up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "transaction"
+ADD FOREIGN KEY ("expense_id") REFERENCES "expense" ("id") ON DELETE CASCADE ON UPDATE CASCADE