New example: splitwise

Author: lovasoa

README.md

@@ -110,6 +110,13 @@ to the user's browser.
 - Create a file called index.sql with the contents from [this example](./index.sql)
 - Open https://localhost:8080 in your browser
 
+
+## Examples
+
+- [Tiny splitwise clone](./examples/splitwise): a shared expense tracker app
+- [Corporate Conundrum](./examples/corporate-conundrum/): a board game implemented in SQL
+- [SQLPage's own official website and documentation](./examples/official-site/): the website you are currently reading
+
 ## Configuration
 
 SQLPage can be configured through either a configuration file placed in `sqlpage/sqlpage.json`

docs/example-splitwise.png

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+# SQL-only expense tracker app
+
+This is a small web application that allows you to track shared expenses with your friends.
+It is built entirely in SQL using SQLPage.
+
+![screenshot](../../docs/example-splitwise.png)

examples/splitwise/README.md

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+-- Write the name of the group in the title of the page
+SELECT 'title' as component, name as contents FROM expense_group WHERE id = $id;
+
+
+-- Handle the form to add a member to the group (we do it at the top of the page to see it right away)
+INSERT INTO group_member(group_id, name)
+SELECT $id, :new_member_name WHERE :new_member_name IS NOT NULL;
+
+-- List of members of the group
+SELECT 'list' as component, 'Membres' as title;
+SELECT name AS title FROM group_member WHERE group_id = $id;
+
+-- Form to add a new member to the group
+SELECT 'form' as component, 'Ajouter un membre au groupe' as validate;
+SELECT 'Nom du membre' AS 'label', 'new_member_name' AS name;
+
+SELECT 'title' as component, 'Dépenses' as contents
+
+-- Form to add an expense
+SELECT 'form' as component, 'Ajouter une dépense' as title, 'Ajouter' as validate;
+SELECT 'Description' AS name;
+SELECT 'Montant' AS name, 'number' AS type;
+SELECT 'Dépensé par' AS name, 'select' as type,
+    json_group_array(json_object("label", name, "value", id)) as options
+FROM group_member WHERE group_id = $id;
+
+-- Insert the expense posted by the form into the database
+INSERT INTO expense(spent_by, name, amount)
+SELECT :"Dépensé par", :Description, :Montant WHERE :Montant IS NOT NULL;
+
+-- List of expenses of the group
+SELECT 'card' as component, 'Dépenses' as title;
+SELECT expense.name as title,
+    'Par ' || group_member.name || ', le ' || expense.date as description,
+    expense.amount || ' €' as footer,
+    CASE
+        WHEN expense.amount > 100 THEN 'red'
+        WHEN expense.amount > 50 THEN 'orange'
+        ELSE 'blue'
+    END AS color
+FROM expense
+    INNER JOIN group_member on expense.spent_by = group_member.id
+WHERE group_member.group_id = $id;
+
+-- Show the positive and negative debts of each member
+SELECT 'chart' AS component, 'Dette par personne' AS title, 'bar' AS type, TRUE AS horizontal;
+SELECT member_name AS label, is_owed AS value FROM individual_debts
+WHERE group_id = $id ORDER BY is_owed DESC;

examples/splitwise/group.sql

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+
+-- Simple form to create a shared expense account
+SELECT 'form' as component,
+    'Nouveau compte partagé' as title,
+    'Créer le compte de dépenses partagé !' as validate;
+SELECT 'Nom du compte' AS label,
+    'shared_expense_name' AS name;
+
+-- Insert the shared expense account posted by the form into the database
+INSERT INTO expense_group(name)
+SELECT :shared_expense_name
+WHERE :shared_expense_name IS NOT NULL;
+
+-- List of shared expense accounts
+-- (we put it after the insertion because we want to see new accounts right away when they are created)
+SELECT 'list' as component;
+SELECT name AS title,
+    'group.sql?id=' || id AS link
+FROM expense_group;

examples/splitwise/index.sql

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+CREATE TABLE expense_group(
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT
+);
+CREATE TABLE group_member(
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    group_id INTEGER REFERENCES expense_group(id),
+    name TEXT
+);
+CREATE TABLE expense(
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    spent_by INTEGER REFERENCES group_member(id),
+    -- identifiant du membre qui a fait la dépense
+    date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    -- date et heure de la dépense
+    name TEXT,
+    -- intitulé
+    amount DECIMAL -- montant en euros
+);

examples/splitwise/sqlpage/migrations/0000_schema.sql

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+-- A view that shows all the expenses of a group, with at least one line per member
+DROP VIEW IF EXISTS members_with_expenses;
+CREATE VIEW members_with_expenses AS
+SELECT group_member.group_id AS group_id,
+    group_member.id AS spent_by_id,
+    COALESCE(expense.amount, 0) AS amount,
+    group_member.name AS spent_by_name
+FROM group_member
+    LEFT JOIN expense on expense.spent_by = group_member.id;
+-- A view that shows the total amount of expense per person of a group
+DROP VIEW IF EXISTS average_debt_per_person;
+CREATE VIEW average_debt_per_person AS
+SELECT group_id,
+    sum(amount) / count(distinct spent_by_id) AS debt
+FROM members_with_expenses
+GROUP BY group_id;
+-- A view that shows the total amount a person is owed in a group
+DROP VIEW IF EXISTS individual_debts;
+CREATE VIEW individual_debts AS
+SELECT members_with_expenses.group_id AS group_id,
+    spent_by_id AS member_id,
+    spent_by_name AS member_name,
+    sum(members_with_expenses.amount) - average_debt_per_person.debt AS is_owed
+FROM members_with_expenses
+    INNER JOIN average_debt_per_person ON average_debt_per_person.group_id = members_with_expenses.group_id
+GROUP BY spent_by_id
+ORDER BY is_owed DESC;