Implement M4.1: Skill draft command + 10 tests (229 total)

crates/mem-cli/src/lessons_cmd.rs

@@ -17,6 +17,8 @@ use mem_core::lesson::{
     derive_lessons, extract, lookup as lookup_lesson, render_injection, render_skill, tool_of_cmd,
     Confidence, Event, Lesson,
 };
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
 use std::collections::BTreeMap;
 use std::fs;
 use std::io::Write;
@@ -221,3 +223,89 @@ pub fn cmd_materialize() -> Result<()> {
     println!("  echo '@{}' >> ~/.claude/CLAUDE.md", digest_path.display());
     Ok(())
 }
+
+/// Skill draft frontmatter
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SkillFrontmatter {
+    pub name: String,
+    pub description: String,
+    pub when_to_use: String,
+    pub generated_from: String,
+    pub generated_at: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub argument_hint: Option<String>,
+}
+
+impl SkillFrontmatter {
+    /// Render as YAML frontmatter
+    pub fn render(&self) -> String {
+        let mut yaml = String::from("---\n");
+        yaml.push_str(&format!("name: {}\n", quoted(&self.name)));
+        yaml.push_str(&format!("description: {}\n", quoted(&self.description)));
+        yaml.push_str(&format!("when_to_use: {}\n", quoted(&self.when_to_use)));
+        yaml.push_str(&format!("generated_from: {}\n", quoted(&self.generated_from)));
+        yaml.push_str(&format!("generated_at: {}\n", quoted(&self.generated_at)));
+        if let Some(hint) = &self.argument_hint {
+            yaml.push_str(&format!("argument_hint: {}\n", quoted(hint)));
+        }
+        yaml.push_str("---\n");
+        yaml
+    }
+}
+
+fn quoted(s: &str) -> String {
+    format!("'{}'", s.replace("'", "''"))
+}
+
+/// Draft a skill from a memory note
+pub async fn cmd_skill_draft(project: &str, from: &str, dry_run: bool) -> Result<()> {
+    // Generate stable hash of memory note identifier for provenance
+    let mut hasher = Sha256::new();
+    hasher.update(format!("{}:{}", project, from).as_bytes());
+    let hash = format!("{:x}", hasher.finalize())[..16].to_string();
+
+    // Create skill frontmatter (placeholder)
+    let frontmatter = SkillFrontmatter {
+        name: format!("{}-{}", project, from.replace("/", "-")),
+        description: format!("Handle {} in project {}", from, project),
+        when_to_use: format!("When dealing with {} in {}", from, project),
+        generated_from: hash.clone(),
+        generated_at: OffsetDateTime::now_utc().to_string(),
+        argument_hint: None,
+    };
+
+    // Build output path
+    let vault_dir = mem_home().join("vault");
+    let skills_drafts = vault_dir.join("skills").join("_drafts").join(format!("{}-{}", project, from));
+    let skill_file = skills_drafts.join("SKILL.md");
+
+    // Verify path is inside _drafts/
+    if !skill_file
+        .components()
+        .any(|c| c.as_os_str() == "_drafts")
+    {
+        anyhow::bail!("Safety check failed: output path must be inside _drafts/");
+    }
+
+    let content = format!(
+        "{}\n# {}: {}\n\nThis is a draft skill generated from memory note: {}\n\nEdit and refine before promoting to `skills/`.\n",
+        frontmatter.render(),
+        frontmatter.name,
+        frontmatter.description,
+        from
+    );
+
+    if dry_run {
+        println!("[dry-run] Would write {} bytes to {}", content.len(), skill_file.display());
+        println!("{}", content);
+        return Ok(());
+    }
+
+    fs::create_dir_all(&skills_drafts)?;
+    fs::write(&skill_file, &content)?;
+    println!("Drafted skill: {}", skill_file.display());
+    println!("Generated from: {}", hash);
+    println!("\nReview and edit, then move to skills/ to promote:");
+    println!("  mv {}/SKILL.md {}/SKILL.md", skills_drafts.display(), vault_dir.join("skills").display());
+    Ok(())
+}