Split bills function and basic template.

budget/models.py

@@ -45,10 +45,57 @@ class Project(db.Model):
 
         for person in self.members:
             balance = should_receive[person] - should_pay[person]
-            balances[person.id] = round(balance, 2)
+            balances[person] = round(balance, 2)
 
         return balances
 
+    def settle_bill(self):
+        """Return a list of transactions that could be made to settle the bill"""
+        balances = self.balance
+        credits, debts = list(), list()
+        transactions = list()
+        # Create lists of credits and debts
+        for person in balances.keys():
+            if balances[person] > 0:
+                credits.append({"person": person, "balance": balances[person]})
+            elif balances[person] < 0:
+                debts.append({"person": person, "balance": -balances[person]})
+        # Try and find exact matches
+        for credit in credits:
+            match = self.exactmatch(credit["balance"], debts)
+            if match:
+                for m in match:
+                    transactions.append({"ower": m["person"], "payer": credit["person"], "amount": m["balance"]})
+                    debts.remove(m)
+                credits.remove(credit)
+        # Split any remaining debts & credits
+        while credits and debts:
+            if credits[0]["balance"] > debts[0]["balance"]:
+                transactions.append({"ower": debts[0]["person"], "payer": credits[0]["person"], "amount": debts[0]["balance"]})
+                credits[0]["balance"] = credits[0]["balance"] - debts[0]["balance"]
+                del debts[0]
+            else:
+                transactions.append({"ower": debts[0]["person"], "payer": credits[0]["person"], "amount": credits[0]["balance"]})
+                debts[0]["balance"] = debts[0]["balance"] - credits[0]["balance"]
+                del credits[0]
+        return transactions
+
+    def exactmatch(self, credit, debts):
+        """Recursively try and find subsets of 'debts' whose sum is equal to credit"""
+        if not debts:
+            return []
+        if debts[0]["balance"] > credit:
+            return self.exactmatch(credit, debts[1:])
+        elif debts[0]["balance"] == credit:
+            return [debts[0]]
+        else:
+            match = self.exactmatch(credit-debts[0]["balance"], debts[1:])
+            if match:
+                match.append(debts[0])
+            else:
+                match = self.exactmatch(credit, debts[1:])
+            return match
+
     def has_bills(self):
         """return if the project do have bills or not"""
         return self.get_bills().count() > 0

budget/templates/layout.html

@@ -54,7 +54,10 @@
     <h3><a class="logo" href="{{ url_for(".home") }}">#! money?</a></h3>
     {% if g.project %}
     <ul class="menu">
+    {% block navbar %}
         <li class="active"><a href="{{ url_for(".list_bills") }}">{{ _("Bills") }}</a></li>
+        <li><a href="{{ url_for(".settle_bill") }}">{{ _("Settle") }}</a></li>
+    {% endblock %}
     </ul>
     <ul class="nav secondary-nav">
       <li class="menu">

budget/templates/list_bills.html

@@ -76,15 +76,15 @@
     <div id="table_overflow">
     <table class="balance">
     {% set balance = g.project.balance %}
-    {% for member in g.project.members | sort(attribute='name') if member.activated or balance[member.id] != 0 %}
-    <tr id="bal-member-{{ member.id }}" action={% if member.activated %}delete{% else %}reactivate{% endif %}>
+    {% for member in g.project.members | sort(attribute='name') if member.activated or balance[member] != 0 %}
+    <tr id="bal-member-{{ member }}" action={% if member.activated %}delete{% else %}reactivate{% endif %}>
         <td class="balance-name">{{ member.name }}</td>
-        <td class="balance-value {% if balance[member.id] > 0 %}positive{% elif balance[member.id] < 0 %}negative{% endif %}">
-            {% if balance[member.id] > 0 %}+{% endif %}{{ balance[member.id] }}
+        <td class="balance-value {% if balance[member] > 0 %}positive{% elif balance[member] < 0 %}negative{% endif %}">
+            {% if balance[member] > 0 %}+{% endif %}{{ balance[member] }}
         </td>
         {% if member.activated %}
         <td class="action delete">
-            <form action="{{ url_for(".remove_member", member_id=member.id) }}" method="POST">
+            <form action="{{ url_for(".remove_member", member_id=member) }}" method="POST">
                 <button type="submit">{{ _("delete") }}</button></form></td>
         {% else %}
         <td class="action reactivate">

budget/templates/settle_bill.html

@@ -0,0 +1,35 @@
+{% extends "layout.html" %}
+
+{% block head %}
+    <script src="{{ url_for("static", filename="js/jquery-ui.js") }}"></script>
+    {% if g.lang != "en" %}
+    <script src="{{ url_for("static", filename="js/i18n/jquery.ui.datepicker-%s.js" % g.lang ) }}"></script>
+    {% endif %}
+{% endblock %}
+{% block js %}
+    $('#cancel-form').click(function(){location.href={{ url_for(".list_bills") }};});
+    $.datepicker.setDefaults({'dateFormat': 'yy-mm-dd'});
+    $(".datepicker").datepicker($.datepicker.regional['{{ g.lang }}']);
+
+{% endblock %}
+{% block navbar %}
+    <li><a href="{{ url_for(".list_bills") }}">{{ _("Bills") }}</a></li>
+    <li class="active"><a href="{{ url_for(".settle_bill") }}">{{ _("Settle") }}</a></li>
+{% endblock %}
+
+
+{% block content %}
+    <table id="bill_table" class="split_bills common-table zebra-striped">
+        <thead><tr><th>{{ _("Who pays?") }}</th><th>{{ _("To whom?") }}</th><th>{{ _("How much?") }}</th></tr></thead>
+    <tbody>
+    {% for bill in bills %}
+    <tr class="{{ loop.cycle("odd", "even") }}" owers={{bill.owers|join(',','id')}} payer={{bill.payer.id}}>
+            <td>{{ bill.ower }}</td>
+            <td>{{ bill.payer }}</td>
+            <td>{{ "%0.2f"|format(bill.amount) }}</td>
+    </tr>
+    {% endfor %}
+    </tbody>
+    </table>
+
+{% endblock %}

budget/web.py

@@ -382,10 +382,11 @@ def change_lang(lang):
     return redirect(request.headers.get('Referer') or url_for('.home'))
 
 
-@main.route("/<project_id>/compute")
-def compute_bills():
+@main.route("/<project_id>/settle_bill")
+def settle_bill():
     """Compute the sum each one have to pay to each other and display it"""
-    return render_template("compute_bills.html")
+    bills = g.project.settle_bill()
+    return render_template("settle_bill.html", bills=bills)
 
 
 @main.route("/<project_id>/archives/create")