Comment PRs with updated schedule information (#1576)

This adds a GH action to add a comment to every PR giving the updated
course schedule with the PR merged.

To accomplish this, I broke `mdbook-course` into a library and two
binaries, allowing the mdbook content to be loaded dynamically outside
of an `mdbook build` invocation.

I think this is a net benefit, but possible improvements include:
* diffing the "before" and "after" schedules and only making the comment
when those are not the same (or replacing the comment with "no schedule
changes")
* including per-segment timing behind `<details>` (with a few minutes
effort I couldn't get this to play nicely with the markdown lists)

---------

Co-authored-by: Martin Geisler <mgeisler@google.com>

.github/workflows/course-schedule.yml

@@ -0,0 +1,27 @@
+name: "Course Schedule Updates"
+on:
+  pull_request:
+    paths:
+      - "src/**.md"
+
+jobs:
+  course-schedule:
+    runs-on: ubuntu-latest
+    name: Make Course Schedule Comment
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Setup Rust cache
+        uses: ./.github/workflows/setup-rust-cache
+
+      - name: Generate Schedule
+        run: cargo run -p mdbook-course --bin course-schedule > course-schedule.md
+
+      - name: Comment PR
+        uses: thollander/actions-comment-pull-request@v2
+        with:
+          filePath: course-schedule.md
+          comment_tag: course-schedule

mdbook-course/README.md

@@ -13,6 +13,7 @@ below:
 
 ```yaml
 minutes: NNN
+target_minutes: NNN
 course: COURSE NAME
 session: SESSION NAME
 ```
@@ -59,6 +60,9 @@ require in the `minutes` field. This information is summed, with breaks
 automatically added between segments, to give time estimates for segments,
 sessions, and courses.
 
+Each session should list a `target_minutes` that is the target duration of the
+session.
+
 ## Directives
 
 Within the course material, the following directives can be used:
@@ -73,3 +77,9 @@ Within the course material, the following directives can be used:
 These will be replaced with a markdown outline of the current segment, session,
 or course. The last directive can refer to another course by name and is used in
 the "Running the Course" section.
+
+# Course-Schedule Comments
+
+The `course-schedule` binary generates Markdown output that is included in a
+GitHub pull request comment, based on the information provided in the above
+format.

mdbook-course/src/bin/course-schedule.rs

@@ -0,0 +1,61 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use mdbook::MDBook;
+use mdbook_course::course::{Course, Courses};
+use mdbook_course::markdown::duration;
+
+fn main() {
+    pretty_env_logger::init();
+    let root_dir = ".";
+    let mdbook = MDBook::load(root_dir).expect("Unable to load the book");
+    let (courses, _) = Courses::extract_structure(mdbook.book)
+        .expect("Unable to extract course structure");
+
+    println!("## Course Schedule");
+    println!("With this pull request applied, the course schedule is as follows:");
+    for course in &courses {
+        print_summary(course);
+    }
+}
+
+fn timediff(actual: u64, target: u64, slop: u64) -> String {
+    if actual > target + slop {
+        format!(
+            "{} (\u{23f0} *{} too long*)",
+            duration(actual),
+            duration(actual - target),
+        )
+    } else if actual < target - slop {
+        format!("{}: ({} short)", duration(actual), duration(target - actual),)
+    } else {
+        format!("{}", duration(actual))
+    }
+}
+
+fn print_summary(course: &Course) {
+    if course.target_minutes() == 0 {
+        return;
+    }
+    println!("### {}", course.name);
+    println!("_{}_", timediff(course.minutes(), course.target_minutes(), 15));
+
+    for session in course {
+        println!(
+            "* {} - _{}_",
+            session.name,
+            timediff(session.minutes(), session.target_minutes(), 5)
+        );
+    }
+}

mdbook-course/src/bin/mdbook-course.rs

@@ -12,17 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-mod course;
-mod frontmatter;
-mod markdown;
-mod replacements;
-mod timing_info;
-
-use crate::course::{Course, Courses};
-use crate::markdown::duration;
 use clap::{Arg, Command};
 use mdbook::book::BookItem;
 use mdbook::preprocess::CmdPreprocessor;
+use mdbook_course::course::Courses;
+use mdbook_course::{replacements, timing_info};
 use std::io::{stdin, stdout};
 use std::process;
 
@@ -46,47 +40,9 @@ fn main() {
     }
 }
 
-fn timediff(actual: u64, target: u64) -> String {
-    if actual > target {
-        format!(
-            "{}: {} OVER TARGET {}",
-            duration(actual),
-            duration(actual - target),
-            duration(target)
-        )
-    } else if actual < target {
-        format!(
-            "{}: {} shorter than target {}",
-            duration(actual),
-            duration(target - actual),
-            duration(target)
-        )
-    } else {
-        format!("{}: right on time", duration(actual))
-    }
-}
-
-fn print_summary(fundamentals: &Course) {
-    eprintln!("Fundamentals: {}", timediff(fundamentals.minutes(), 8 * 3 * 60));
-
-    eprintln!("Sessions:");
-    for session in fundamentals {
-        eprintln!("  {}: {}", session.name, timediff(session.minutes(), 3 * 60));
-        for segment in session {
-            eprintln!("    {}: {}", segment.name, duration(segment.minutes()));
-        }
-    }
-}
-
 fn preprocess() -> anyhow::Result<()> {
-    let (ctx, book) = CmdPreprocessor::parse_input(stdin())?;
+    let (_, book) = CmdPreprocessor::parse_input(stdin())?;
     let (courses, mut book) = Courses::extract_structure(book)?;
-    let verbose = ctx
-        .config
-        .get_preprocessor("course")
-        .and_then(|t| t.get("verbose"))
-        .and_then(|v| v.as_bool())
-        .unwrap_or_default();
 
     book.for_each_mut(|chapter| {
         if let BookItem::Chapter(chapter) = chapter {
@@ -108,15 +64,6 @@ fn preprocess() -> anyhow::Result<()> {
         }
     });
 
-    // Print a summary of times for the "Fundamentals" course.
-    // Translations with a POT-Creation-Date before 2023-11-29 (when
-    // we merged #1073) will have no frontmatter.
-    if verbose {
-        if let Some(fundamentals) = courses.find_course("Fundamentals") {
-            print_summary(fundamentals);
-        }
-    }
-
     serde_json::to_writer(stdout(), &book)?;
     Ok(())
 }

mdbook-course/src/course.rs

@@ -72,6 +72,7 @@ pub struct Course {
 pub struct Session {
     pub name: String,
     pub segments: Vec<Segment>,
+    target_minutes: u64,
 }
 
 /// A Segment is a collection of slides with a related theme.
@@ -143,6 +144,7 @@ impl Courses {
             {
                 let course = courses.course_mut(course_name);
                 let session = course.session_mut(session_name);
+                session.target_minutes += frontmatter.target_minutes.unwrap_or(0);
                 session.add_segment(frontmatter, chapter)?;
             }
         }
@@ -232,6 +234,15 @@ impl Course {
         self.into_iter().map(|s| s.minutes()).sum()
     }
 
+    /// Return the target duration of this course, as the sum of all segment
+    /// target durations.
+    ///
+    /// This includes breaks between segments, but does not count time between
+    /// sessions.
+    pub fn target_minutes(&self) -> u64 {
+        self.into_iter().map(|s| s.target_minutes()).sum()
+    }
+
     /// Generate a Markdown schedule for this course, for placement at the given
     /// path.
     pub fn schedule(&self, at_source_path: impl AsRef<Path>) -> String {
@@ -333,6 +344,17 @@ impl Session {
             * BREAK_DURATION;
         instructional_time + breaks
     }
+
+    /// Return the target duration of this session.
+    ///
+    /// This includes breaks between segments.
+    pub fn target_minutes(&self) -> u64 {
+        if self.target_minutes > 0 {
+            self.target_minutes
+        } else {
+            self.minutes()
+        }
+    }
 }
 
 impl<'a> IntoIterator for &'a Session {

mdbook-course/src/frontmatter.rs

@@ -20,6 +20,7 @@ use serde::Deserialize;
 #[derive(Deserialize, Debug, Default)]
 pub struct Frontmatter {
     pub minutes: Option<u64>,
+    pub target_minutes: Option<u64>,
     pub course: Option<String>,
     pub session: Option<String>,
 }

mdbook-course/src/lib.rs

@@ -0,0 +1,19 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub mod course;
+pub mod frontmatter;
+pub mod markdown;
+pub mod replacements;
+pub mod timing_info;

src/welcome-day-1-afternoon.md

@@ -1,5 +1,6 @@
 ---
 session: Day 1 Afternoon
+target_minutes: 180
 ---
 
 # Welcome Back

src/welcome-day-1.md

@@ -2,6 +2,7 @@
 minutes: 5
 course: Fundamentals
 session: Day 1 Morning
+target_minutes: 180
 ---
 
 # Welcome to Day 1

src/welcome-day-2-afternoon.md

@@ -1,5 +1,6 @@
 ---
 session: Day 2 Afternoon
+target_minutes: 180
 ---
 
 # Welcome Back

src/welcome-day-2.md

@@ -2,6 +2,7 @@
 minutes: 3
 course: Fundamentals
 session: Day 2 Morning
+target_minutes: 180
 ---
 
 # Welcome to Day 2

src/welcome-day-3-afternoon.md

@@ -1,5 +1,6 @@
 ---
 session: Day 3 Afternoon
+target_minutes: 180
 ---
 
 # Welcome Back

src/welcome-day-3.md

@@ -2,6 +2,7 @@
 minutes: 3
 course: Fundamentals
 session: Day 3 Morning
+target_minutes: 180
 ---
 
 # Welcome to Day 3

src/welcome-day-4-afternoon.md

@@ -1,5 +1,6 @@
 ---
 session: Day 4 Afternoon
+target_minutes: 180
 ---
 
 # Welcome Back

src/welcome-day-4.md

@@ -2,6 +2,7 @@
 minutes: 3
 course: Fundamentals
 session: Day 4 Morning
+target_minutes: 180
 ---
 
 # Welcome to Day 4