Function merge_items_into_section

atomic-agent/src/learnings.rs:526–602

Merge new items into existing section headings without duplicating headings. If `### Repo` already exists in the section, new repo items are appended under the existing heading. If a heading doesn't exist yet, it's created.

(
    existing_content: &str,
    new_items: &HashMap<String, Vec<String>>,
)

/// If `### Repo` already exists in the section, new repo items are appended
/// under the existing heading. If a heading doesn't exist yet, it's created.
fn merge_items_into_section(
    existing_content: &str,
    new_items: &HashMap<String, Vec<String>>,
) -> String {
    let start_idx = match existing_content.find(SECTION_START) {
        Some(idx) => idx + SECTION_START.len(),
        None => return existing_content.to_string(),
    };

    let end_marker_idx = match existing_content[start_idx..].find(SECTION_END) {
        Some(idx) => start_idx + idx,
        None => return existing_content.to_string(),
    };

    let before_section = &existing_content[..start_idx];
    let section_body = &existing_content[start_idx..end_marker_idx];
    let after_section = &existing_content[end_marker_idx..];

    // Parse existing section into heading → items
    let mut sections: Vec<(String, Vec<String>)> = Vec::new();
    let mut current_heading: Option<String> = None;
    let mut current_items: Vec<String> = Vec::new();

    for line in section_body.lines() {
        let trimmed = line.trim();
        if trimmed.starts_with("### ") {
            // Save previous heading if any
            if let Some(heading) = current_heading.take() {
                sections.push((heading, std::mem::take(&mut current_items)));
            }
            current_heading = Some(trimmed.to_string());
        } else if trimmed.starts_with("- ") {
            current_items.push(trimmed.to_string());
        }
    }
    if let Some(heading) = current_heading {
        sections.push((heading, current_items));
    }

    // Merge new items into existing headings or append new headings
    let mut merged_headings: std::collections::HashSet<String> = std::collections::HashSet::new();
    for (heading, items) in sections.iter_mut() {
        if let Some(new) = new_items.get(heading) {
            items.extend(new.iter().cloned());
            merged_headings.insert(heading.clone());
        }
    }

    // Add headings that didn't exist yet
    // Use a stable order: Repo first, then Workflow
    for heading in &["### Repo", "### Workflow"] {
        let heading = heading.to_string();
        if !merged_headings.contains(&heading) {
            if let Some(items) = new_items.get(&heading) {
                sections.push((heading, items.clone()));
            }
        }
    }