Backend: Proof of concept of email templating rev

Author: tristanlabelle

app/backend/src/couchers/email/templating.py

@@ -0,0 +1,146 @@
+from dataclasses import dataclass
+import re
+from typing import Any
+
+from couchers.templates.v2 import template_folder, render_template, Context
+
+@dataclass
+class EmailContent:
+    subject: str
+    preview: str
+    body: list[BodySection]
+    unsubscribe_info: UnsubscribeInfo | None # None if security critical
+
+@dataclass
+class BodySection:
+    """Base class for email sections."""
+    pass
+
+@dataclass
+class TextSection(BodySection):
+    text: str
+
+@dataclass
+class ButtonSection(BodySection):
+    url: str
+    text: str
+
+@dataclass
+class PersonSection(BodySection):
+    name: str
+    age: int
+    city: str
+    avatar_url: str
+    text: str | None
+
+@dataclass
+class QuoteSection(BodySection):
+    text: str
+
+@dataclass
+class UnsubscribeInfo:
+    topic_text: str | None
+    topic_url: str | None
+    topic_action_text: str | None
+    topic_action_url: str | None
+
+@dataclass
+class EmailTemplate:
+    """jinja templates for the different parts of an email."""
+
+    header: str | None
+    footer: str | None
+    text_section: str
+    button_section: str
+    person_section: str
+    quote_section: str
+
+_SECTION_RE = re.compile(r"""
+<!-- begin-section:(?P<name>\w+) -->\s*
+(?P<snippet>[\s\S]*?)
+\s*<!-- end-section:(?P=name) -->
+""".strip(), re.MULTILINE)
+
+def load_html_template() -> EmailTemplate:
+    full_template = (template_folder / "generated_html" / "prototype.html").read_text(encoding="utf8")
+    section_matches = list(_SECTION_RE.finditer(full_template))
+
+    header = full_template[:section_matches[0].start()]
+    footer = full_template[section_matches[-1].end():]
+    sections = { match.group("name"): match.group("snippet") for match in section_matches }
+
+    return EmailTemplate(
+        header=header,
+        footer=footer,
+        text_section=sections["text"],
+        button_section=sections["button"],
+        person_section=sections["person"],
+        quote_section=sections["quote"],
+    )
+
+def load_text_template() -> EmailTemplate:
+    return EmailTemplate(
+        header="",
+        footer=(template_folder / "_footer.txt").read_text("utf8"),
+        text_section="{{ text }}",
+        button_section="{{ label }}: {{ url }}",
+        person_section="{{ name }}, {{ age }}\n{{ city }}",
+        quote_section="> {{ text }}"
+    )
+
+def render_email(content: EmailContent, template: EmailTemplate, context: Context) -> str:
+    email_str = ""
+
+    if template.header:
+        email_str = render_template(template.header, {
+            "header_subject": content.subject,
+            "header_preview": content.preview,
+        }, context)
+
+    email_str += "\n"
+    email_str += "\n"
+
+    for section in content.body:
+        match section:
+            case TextSection():
+                email_str += render_template(template.text_section, {
+                    "text": section.text
+                }, context)
+            case ButtonSection():
+                email_str += render_template(template.button_section, {
+                    "url": section.url,
+                    "label": section.text
+                }, context)
+            case PersonSection():
+                email_str += render_template(template.person_section, {
+                    "name": section.name,
+                    "age": section.age,
+                    "city": section.city,
+                    "avatar_url": section.avatar_url
+                }, context)
+            case QuoteSection():
+                email_str += render_template(template.quote_section, {
+                    "text": section.text
+                }, context)
+            case _:
+                assert False, "Unexpected section!"
+
+        email_str += "\n"
+        email_str += "\n"
+
+    if template.footer:
+        footer_args: dict[str, Any] = {
+            "footer_email_is_critical": content.unsubscribe_info is None
+        }
+        # if content.unsubscribe_info:
+        #     footer_args["footer_manage_notifications_link"] = urls.notification_settings_link()
+        #     footer_args["footer_notification_topic_action"] = rendered.topic_action_unsubscribe_text
+        #     footer_args["footer_notification_topic_action_link"] = generate_unsub_topic_action(notification)
+        #     footer_args["footer_notification_topic_key"] = rendered.topic_key_unsubscribe_text
+        #     footer_args["footer_notification_topic_key_link"] = generate_unsub_topic_key(notification)
+        #     footer_args["footer_do_not_email_link"] = generate_do_not_email(user)
+
+        email_str += render_template(template.footer, footer_args, context)
+
+    return email_str
+

app/backend/src/tests/test_email_templating.py

@@ -0,0 +1,38 @@
+import logging
+from pathlib import Path
+
+from couchers.email.templating import EmailContent, EmailTemplate, TextSection, ButtonSection, QuoteSection, load_html_template, load_text_template, render_email
+from couchers.templates.v2 import Context, template_folder
+
+logger = logging.getLogger(__name__)
+
+def test_email_templating() -> None:
+    email = EmailContent(
+        subject="New host request from Bob",
+        preview="Preview",
+        body=[
+            TextSection(text="You received a request from Bob"),
+            QuoteSection(text="Yo can you host me?"),
+            ButtonSection(url="https://foo", text="Accept"),
+            TextSection(text="Yours truly, Couchers"),
+        ],
+        unsubscribe_info=None
+    )
+
+    html_template = load_html_template()
+    html = render_email(email, html_template, Context(timezone=None, locale="en", plaintext=False))
+    Path(__file__ + ".out.html").write_text(html, encoding="utf8")
+
+    plaintext_template = EmailTemplate(
+        header="",
+        footer=(template_folder / "_footer.txt").read_text("utf8"),
+        text_section="{{ text }}",
+        button_section="{{ label }}: {{ url }}",
+        person_section="{{ name }}, {{ age }}\n{{ city }}",
+        quote_section="> {{ text }}"
+    )
+
+    plaintext_template = load_text_template()
+    plaintext = render_email(email, plaintext_template, Context(timezone=None, locale="en", plaintext=True))
+    Path(__file__ + ".out.txt").write_text(plaintext, encoding="utf8")
+