//! Collect resident-injection candidates from the workspace.
//!
//! Walks `<workspace>/knowledge/*.md`, returns the records whose
//! frontmatter has `model_invokation: true` as `(slug, description)`
//! pairs sorted by slug. The Pod system-prompt assembler appends them
//! into the trailing section so descriptions sit next to the scope
//! summary and AGENTS.md.
//!
//! Files that fail to read or parse are skipped silently — the Linter
//! enforces shape on write, so a malformed file here means external
//! tampering and we'd rather degrade than panic.

use crate::schema::{KnowledgeFrontmatter, split_frontmatter};
use crate::workspace::WorkspaceLayout;

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ResidentKnowledgeEntry {
    pub slug: String,
    pub description: String,
}

/// Walk `<workspace>/knowledge/*.md` and return entries whose
/// frontmatter has `model_invokation: true`, sorted by slug. A missing
/// `knowledge/` directory yields an empty vec.
pub fn collect_resident_knowledge(layout: &WorkspaceLayout) -> Vec<ResidentKnowledgeEntry> {
    let dir = layout.knowledge_dir();
    let entries = match std::fs::read_dir(&dir) {
        Ok(it) => it,
        Err(_) => return Vec::new(),
    };

    let mut out: Vec<ResidentKnowledgeEntry> = Vec::new();
    for entry in entries.flatten() {
        let path = entry.path();
        if !path.is_file() {
            continue;
        }
        let name = match path.file_name().and_then(|n| n.to_str()) {
            Some(n) => n,
            None => continue,
        };
        let slug = match name.strip_suffix(".md") {
            Some(s) => s.to_string(),
            None => continue,
        };
        let raw = match std::fs::read_to_string(&path) {
            Ok(s) => s,
            Err(_) => continue,
        };
        let (yaml, _body) = match split_frontmatter(&raw) {
            Ok(v) => v,
            Err(_) => continue,
        };
        let fm: KnowledgeFrontmatter = match serde_yaml::from_str(yaml) {
            Ok(f) => f,
            Err(_) => continue,
        };
        if fm.model_invokation {
            out.push(ResidentKnowledgeEntry {
                slug,
                description: fm.description,
            });
        }
    }
    out.sort_by(|a, b| a.slug.cmp(&b.slug));
    out
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::Utc;
    use std::path::Path;
    use tempfile::TempDir;

    fn now() -> String {
        Utc::now().to_rfc3339()
    }

    fn write_knowledge(
        dir: &Path,
        slug: &str,
        description: &str,
        model_invokation: bool,
        body: &str,
    ) {
        let path = dir.join(".insomnia/knowledge").join(format!("{slug}.md"));
        let content = format!(
            "---\ncreated_at: {n}\nupdated_at: {n}\nkind: policy\ndescription: \"{description}\"\nmodel_invokation: {flag}\nuser_invocable: true\nlast_sources: []\n---\n{body}",
            n = now(),
            flag = model_invokation,
        );
        std::fs::write(path, content).unwrap();
    }

    fn setup() -> (TempDir, WorkspaceLayout) {
        let dir = TempDir::new().unwrap();
        std::fs::create_dir_all(dir.path().join(".insomnia/knowledge")).unwrap();
        let layout = WorkspaceLayout::new(dir.path().to_path_buf());
        (dir, layout)
    }

    #[test]
    fn missing_knowledge_dir_returns_empty() {
        let dir = TempDir::new().unwrap();
        // No knowledge/ directory at all.
        let layout = WorkspaceLayout::new(dir.path().to_path_buf());
        assert!(collect_resident_knowledge(&layout).is_empty());
    }

    #[test]
    fn picks_only_model_invokation_true() {
        let (dir, layout) = setup();
        write_knowledge(dir.path(), "alpha", "alpha desc", true, "body\n");
        write_knowledge(dir.path(), "beta", "beta desc", false, "body\n");
        write_knowledge(dir.path(), "gamma", "gamma desc", true, "body\n");

        let got = collect_resident_knowledge(&layout);
        assert_eq!(got.len(), 2);
        assert_eq!(got[0].slug, "alpha");
        assert_eq!(got[0].description, "alpha desc");
        assert_eq!(got[1].slug, "gamma");
        assert_eq!(got[1].description, "gamma desc");
    }

    #[test]
    fn entries_are_sorted_by_slug() {
        let (dir, layout) = setup();
        write_knowledge(dir.path(), "zeta", "z", true, "");
        write_knowledge(dir.path(), "alpha", "a", true, "");
        write_knowledge(dir.path(), "mu", "m", true, "");

        let got = collect_resident_knowledge(&layout);
        let slugs: Vec<&str> = got.iter().map(|e| e.slug.as_str()).collect();
        assert_eq!(slugs, vec!["alpha", "mu", "zeta"]);
    }

    #[test]
    fn malformed_frontmatter_is_skipped() {
        let (dir, layout) = setup();
        write_knowledge(dir.path(), "good", "ok", true, "");
        // Garbage in frontmatter — must be skipped, not panic.
        std::fs::write(
            dir.path().join(".insomnia/knowledge/bad.md"),
            "---\nthis is not yaml: : :\n---\nbody\n",
        )
        .unwrap();

        let got = collect_resident_knowledge(&layout);
        assert_eq!(got.len(), 1);
        assert_eq!(got[0].slug, "good");
    }

    #[test]
    fn non_md_files_ignored() {
        let (dir, layout) = setup();
        write_knowledge(dir.path(), "good", "ok", true, "");
        std::fs::write(
            dir.path().join(".insomnia/knowledge/note.txt"),
            "not markdown\n",
        )
        .unwrap();

        let got = collect_resident_knowledge(&layout);
        assert_eq!(got.len(), 1);
    }
}