feat: show release notes after updates

1 files changed, 154 insertions, 0 deletions

diff --git a/src/release_notes.rs b/src/release_notes.rs
new file mode 100644
index 00000000..fcee9a41
--- /dev/null
+++ b/src/release_notes.rs
@@ -0,0 +1,154 @@
+use std::fs;
+use std::path::{Path, PathBuf};
+
+use serde::{Deserialize, Serialize};
+
+const PENDING_RELEASE_NOTES_PATH: &str = "release-notes.json";
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ReleaseNotes {
+    pub version: String,
+    pub body: String,
+    pub preview: bool,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+struct StoredReleaseNotes {
+    version: String,
+    body: String,
+}
+
+pub fn pending_path() -> PathBuf {
+    let mut path = crate::config::config_path();
+    path.set_file_name(PENDING_RELEASE_NOTES_PATH);
+    path
+}
+
+pub fn save_pending(version: &str, body: &str) -> std::io::Result<()> {
+    save_pending_to_path(&pending_path(), version, body)
+}
+
+fn save_pending_to_path(path: &Path, version: &str, body: &str) -> std::io::Result<()> {
+    let body = normalize_body(body);
+    if body.is_empty() {
+        return clear_pending_at(path);
+    }
+
+    if let Some(parent) = path.parent() {
+        fs::create_dir_all(parent)?;
+    }
+
+    let stored = StoredReleaseNotes {
+        version: version.to_string(),
+        body,
+    };
+    let json = serde_json::to_string_pretty(&stored).map_err(std::io::Error::other)?;
+    let tmp_path = path.with_extension(format!("json.tmp.{}", std::process::id()));
+    fs::write(&tmp_path, json)?;
+    if let Err(err) = fs::rename(&tmp_path, path) {
+        let _ = fs::remove_file(&tmp_path);
+        return Err(err);
+    }
+    Ok(())
+}
+
+pub fn load_pending_for_current_version() -> Option<ReleaseNotes> {
+    load_pending_from_path(&pending_path(), env!("CARGO_PKG_VERSION"))
+}
+
+fn load_pending_from_path(path: &Path, current_version: &str) -> Option<ReleaseNotes> {
+    let content = fs::read_to_string(path).ok()?;
+    let stored: StoredReleaseNotes = serde_json::from_str(&content).ok()?;
+    if stored.version != current_version {
+        return None;
+    }
+
+    let body = normalize_body(&stored.body);
+    if body.is_empty() {
+        return None;
+    }
+
+    Some(ReleaseNotes {
+        version: stored.version,
+        body,
+        preview: false,
+    })
+}
+
+pub fn clear_pending() -> std::io::Result<()> {
+    clear_pending_at(&pending_path())
+}
+
+fn clear_pending_at(path: &Path) -> std::io::Result<()> {
+    if path.exists() {
+        fs::remove_file(path)
+    } else {
+        Ok(())
+    }
+}
+
+pub fn load_preview_from_local_changelog(version: &str) -> Option<ReleaseNotes> {
+    let path = Path::new("CHANGELOG.md");
+    let content = fs::read_to_string(path).ok()?;
+    let body = extract_version_section(&content, version)?;
+    Some(ReleaseNotes {
+        version: version.to_string(),
+        body: normalize_body(&body),
+        preview: true,
+    })
+}
+
+fn extract_version_section(content: &str, version: &str) -> Option<String> {
+    let header = format!("## [{version}]");
+    let mut collecting = false;
+    let mut lines = Vec::new();
+
+    for line in content.lines() {
+        if !collecting {
+            if line.starts_with(&header) {
+                collecting = true;
+            }
+            continue;
+        }
+
+        if line.starts_with("## [") {
+            break;
+        }
+
+        lines.push(line);
+    }
+
+    let body = lines.join("\n").trim().to_string();
+    (!body.is_empty()).then_some(body)
+}
+
+pub fn normalize_body(body: &str) -> String {
+    body.lines()
+        .map(str::trim_end)
+        .collect::<Vec<_>>()
+        .join("\n")
+        .trim()
+        .to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn extracts_version_section() {
+        let changelog = "# Changelog\n\n## [0.2.3] - 2026-03-31\n\n### Changed\n- One\n\n## [0.2.2] - 2026-03-30\n\n### Fixed\n- Two\n";
+        assert_eq!(
+            extract_version_section(changelog, "0.2.3").as_deref(),
+            Some("### Changed\n- One")
+        );
+    }
+
+    #[test]
+    fn preserves_headings() {
+        assert_eq!(
+            normalize_body("### Changed\n- One\n\n### Fixed\n- Two"),
+            "### Changed\n- One\n\n### Fixed\n- Two"
+        );
+    }
+}