netsky-core 0.1.5

//! Prompt loading, templating, and addendum layering.
//!
//! Base prompt + per-agent stanza are embedded at compile time via
//! `include_str!` from the top-level `prompts/` directory. The cwd
//! addendum is read at runtime. Everything is strictly appended — no
//! overrides. See `briefs/netsky-rewrite-v1.md` for the contract.
//!
//! Templating is intentionally minimal: we substitute a small set of
//! named variables (`{{ n }}`, `{{ agent_name }}`, `{{ cwd }}`). No
//! conditionals, no loops. After substitution we assert no `{{`
//! remains — an unsubstituted placeholder is a render bug, not a
//! silent passthrough.

use std::path::Path;

use crate::agent::AgentId;
use crate::consts::{CWD_ADDENDUM_AGENT0, CWD_ADDENDUM_AGENTINFINITY, CWD_ADDENDUM_CLONE_EXT};

// Relative path is resolved against the file doing the `include_str!`
// (this file, at src/crates/netsky-core/src/prompt.rs). The `../../../../`
// backs out to the repo root, where `prompts/` lives.
const BASE_TEMPLATE: &str = include_str!("../prompts/base.md");
const AGENT0_STANZA: &str = include_str!("../prompts/agent0.md");
const CLONE_STANZA: &str = include_str!("../prompts/clone.md");
const AGENTINFINITY_STANZA: &str = include_str!("../prompts/agentinfinity.md");

const SEPARATOR: &str = "\n\n---\n\n";

/// Template variables made available to the render layer.
#[derive(Debug, Clone)]
pub struct PromptContext {
    pub agent: AgentId,
    pub cwd: String,
}

impl PromptContext {
    pub fn new(agent: AgentId, cwd: impl Into<String>) -> Self {
        Self {
            agent,
            cwd: cwd.into(),
        }
    }

    /// Each template variable paired with its rendered value. Stringified
    /// uniformly (including `n`) to avoid the arithmetic-on-string trap
    /// that Tera-style typed contexts enabled.
    fn bindings(&self) -> Vec<(&'static str, String)> {
        vec![
            ("agent_name", self.agent.name()),
            ("n", self.agent.env_n()),
            ("cwd", self.cwd.clone()),
        ]
    }
}

#[derive(Debug)]
pub enum PromptError {
    Io(std::io::Error),
    UnsubstitutedPlaceholders { count: usize, preview: String },
}

impl std::fmt::Display for PromptError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Io(e) => write!(f, "io error reading addendum: {e}"),
            Self::UnsubstitutedPlaceholders { count, preview } => write!(
                f,
                "template render left {count} unsubstituted placeholder(s): {preview}"
            ),
        }
    }
}

impl std::error::Error for PromptError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            Self::Io(e) => Some(e),
            _ => None,
        }
    }
}

impl From<std::io::Error> for PromptError {
    fn from(e: std::io::Error) -> Self {
        Self::Io(e)
    }
}

fn stanza_for(agent: AgentId) -> &'static str {
    match agent {
        AgentId::Agent0 => AGENT0_STANZA,
        AgentId::Clone(_) => CLONE_STANZA,
        AgentId::Agentinfinity => AGENTINFINITY_STANZA,
    }
}

/// Return the filename of the cwd addendum for `agent`: `0.md`,
/// `agentinfinity.md`, or `<N>.md` for clones.
fn cwd_addendum_filename(agent: AgentId) -> String {
    match agent {
        AgentId::Agent0 => CWD_ADDENDUM_AGENT0.to_string(),
        AgentId::Agentinfinity => CWD_ADDENDUM_AGENTINFINITY.to_string(),
        AgentId::Clone(n) => format!("{n}{CWD_ADDENDUM_CLONE_EXT}"),
    }
}

/// Resolve which addendum file to read for `agent`. Consults
/// `netsky.toml` `[addendum]` first; falls back to the conventional
/// filename (`0.md` / `<N>.md` / `agentinfinity.md`) at the root of
/// `cwd`. The TOML path is interpreted relative to `cwd` unless it
/// starts with `/` (absolute) or `~/` (home-relative).
///
/// Per `briefs/netsky-config-design.md` section 3, this lets the owner
/// split per-machine context out of the repo-tracked `0.md` (which is
/// shared across machines) into machine-specific files under `addenda/`
/// without touching code. Missing TOML or missing field = today's
/// behavior unchanged.
fn resolve_addendum_path(agent: AgentId, cwd: &Path) -> std::path::PathBuf {
    use crate::config::Config;

    let configured = Config::load_from(&cwd.join("netsky.toml"))
        .ok()
        .flatten()
        .and_then(|cfg| cfg.addendum)
        .and_then(|a| match agent {
            AgentId::Agent0 => a.agent0,
            AgentId::Agentinfinity => a.agentinfinity,
            AgentId::Clone(_) => a.clone_default,
        });

    match configured {
        Some(p) if p.starts_with('/') => std::path::PathBuf::from(p),
        Some(p) if p.starts_with("~/") => {
            if let Some(home) = dirs::home_dir() {
                home.join(p.trim_start_matches("~/"))
            } else {
                cwd.join(p)
            }
        }
        Some(p) => cwd.join(p),
        None => cwd.join(cwd_addendum_filename(agent)),
    }
}

/// Read the cwd addendum for `agent` from `cwd`. Returns `None` if the
/// file doesn't exist (missing is fine — addenda are optional). Path
/// resolution consults `netsky.toml` `[addendum]` first per
/// [`resolve_addendum_path`].
fn read_cwd_addendum(agent: AgentId, cwd: &Path) -> Result<Option<String>, std::io::Error> {
    let path = resolve_addendum_path(agent, cwd);
    match std::fs::read_to_string(&path) {
        Ok(s) => Ok(Some(s)),
        Err(e) => match e.kind() {
            // Both "no such file" and "cwd isn't even a directory" mean
            // simply: no addendum here. Missing is the common case.
            std::io::ErrorKind::NotFound | std::io::ErrorKind::NotADirectory => Ok(None),
            _ => Err(e),
        },
    }
}

/// Substitute `{{ name }}` (tolerant of inner whitespace) for each
/// binding in `body`. Intentionally does NOT recurse, so replacement
/// values containing `{{ }}` stay literal.
fn apply_bindings(body: &str, bindings: &[(&'static str, String)]) -> String {
    let mut out = body.to_string();
    for (name, value) in bindings {
        // Cover the two spellings we use in templates: `{{ name }}` and
        // `{{name}}`. Tera tolerated arbitrary whitespace; we only need
        // the two canonical forms — pick up the third if anyone ever
        // writes `{{name }}` or `{{ name}}`.
        for placeholder in [
            format!("{{{{ {name} }}}}"),
            format!("{{{{{name}}}}}"),
            format!("{{{{ {name}}}}}"),
            format!("{{{{{name} }}}}"),
        ] {
            out = out.replace(&placeholder, value);
        }
    }
    out
}

/// After render, `{{` should not appear anywhere. If it does, someone
/// added a new template variable without wiring it into PromptContext.
fn assert_fully_rendered(body: &str) -> Result<(), PromptError> {
    let count = body.matches("{{").count();
    if count == 0 {
        return Ok(());
    }
    let preview = body
        .match_indices("{{")
        .take(3)
        .map(|(i, _)| {
            let end = body.len().min(i + 32);
            body[i..end].to_string()
        })
        .collect::<Vec<_>>()
        .join(" | ");
    Err(PromptError::UnsubstitutedPlaceholders { count, preview })
}

/// Render the full system prompt for `agent` from its `cwd`:
/// base + `---` + per-agent stanza + `---` + cwd addendum (if present).
pub fn render_prompt(ctx: PromptContext, cwd: &Path) -> Result<String, PromptError> {
    let agent = ctx.agent;
    let bindings = ctx.bindings();

    let base = apply_bindings(BASE_TEMPLATE, &bindings);
    let stanza = apply_bindings(stanza_for(agent), &bindings);

    let mut out = String::with_capacity(base.len() + stanza.len() + 128);
    out.push_str(base.trim_end());
    out.push_str(SEPARATOR);
    out.push_str(stanza.trim_end());

    if let Some(addendum) = read_cwd_addendum(agent, cwd)? {
        let trimmed = addendum.trim();
        if !trimmed.is_empty() {
            out.push_str(SEPARATOR);
            out.push_str(trimmed);
        }
    }
    out.push('\n');

    assert_fully_rendered(&out)?;
    Ok(out)
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::path::PathBuf;

    fn ctx_for(agent: AgentId) -> PromptContext {
        PromptContext::new(agent, "/tmp/netsky-test")
    }

    #[test]
    fn renders_all_agents_without_addendum() {
        let nowhere = PathBuf::from("/dev/null/does-not-exist");
        for agent in [
            AgentId::Agent0,
            AgentId::Clone(1),
            AgentId::Clone(8),
            AgentId::Agentinfinity,
        ] {
            let out = render_prompt(ctx_for(agent), &nowhere).unwrap();
            assert!(!out.is_empty(), "empty prompt for {agent}");
            assert!(out.contains("---"), "missing separator for {agent}");
            assert!(!out.contains("{{"), "unsubstituted placeholder for {agent}");
        }
    }

    #[test]
    fn clone_prompt_substitutes_n() {
        let nowhere = PathBuf::from("/dev/null/does-not-exist");
        let out = render_prompt(ctx_for(AgentId::Clone(5)), &nowhere).unwrap();
        assert!(out.contains("agent5"));
        assert!(!out.contains("{{ n }}"));
    }

    #[test]
    fn cwd_addendum_is_appended() {
        let tmp = tempfile::tempdir().unwrap();
        std::fs::write(tmp.path().join("0.md"), "USER POLICY HERE").unwrap();
        let out = render_prompt(ctx_for(AgentId::Agent0), tmp.path()).unwrap();
        assert!(out.contains("USER POLICY HERE"));
    }

    #[test]
    fn render_rejects_unsubstituted_placeholder() {
        let body = "hello {{ unknown_var }} world";
        let err = assert_fully_rendered(body).unwrap_err();
        match err {
            PromptError::UnsubstitutedPlaceholders { count, .. } => assert_eq!(count, 1),
            _ => panic!("wrong error variant"),
        }
    }

    #[test]
    fn bindings_stringify_uniformly() {
        // agent0 = "0", clone = "5", agentinfinity = "infinity" — all strings.
        let b0 = PromptContext::new(AgentId::Agent0, "/").bindings();
        let b5 = PromptContext::new(AgentId::Clone(5), "/").bindings();
        let binf = PromptContext::new(AgentId::Agentinfinity, "/").bindings();
        assert_eq!(lookup(&b0, "n"), "0");
        assert_eq!(lookup(&b5, "n"), "5");
        assert_eq!(lookup(&binf, "n"), "infinity");
    }

    fn lookup(bindings: &[(&'static str, String)], key: &str) -> String {
        bindings.iter().find(|(k, _)| *k == key).unwrap().1.clone()
    }

    #[test]
    fn netsky_toml_addendum_overrides_default_path() {
        // Owner splits 0.md into addenda/0-personal.md; netsky.toml
        // routes agent0 to the new path. The default 0.md MUST be
        // ignored when the TOML override is set.
        let tmp = tempfile::tempdir().unwrap();
        std::fs::write(tmp.path().join("0.md"), "OLD POLICY").unwrap();
        std::fs::create_dir_all(tmp.path().join("addenda")).unwrap();
        std::fs::write(tmp.path().join("addenda/0-personal.md"), "NEW POLICY").unwrap();
        std::fs::write(
            tmp.path().join("netsky.toml"),
            "schema_version = 1\n[addendum]\nagent0 = \"addenda/0-personal.md\"\n",
        )
        .unwrap();

        let out = render_prompt(ctx_for(AgentId::Agent0), tmp.path()).unwrap();
        assert!(
            out.contains("NEW POLICY"),
            "TOML override should pick up addenda/0-personal.md"
        );
        assert!(
            !out.contains("OLD POLICY"),
            "TOML override should bypass the legacy 0.md fallback"
        );
    }

    #[test]
    fn missing_netsky_toml_falls_back_to_legacy_addendum() {
        // No netsky.toml at all -> read 0.md as before.
        let tmp = tempfile::tempdir().unwrap();
        std::fs::write(tmp.path().join("0.md"), "LEGACY ADDENDUM").unwrap();
        let out = render_prompt(ctx_for(AgentId::Agent0), tmp.path()).unwrap();
        assert!(out.contains("LEGACY ADDENDUM"));
    }

    #[test]
    fn netsky_toml_without_addendum_section_falls_back() {
        // netsky.toml present but no [addendum] section -> still 0.md.
        let tmp = tempfile::tempdir().unwrap();
        std::fs::write(tmp.path().join("0.md"), "FALLBACK POLICY").unwrap();
        std::fs::write(
            tmp.path().join("netsky.toml"),
            "schema_version = 1\n[owner]\nname = \"Alice\"\n",
        )
        .unwrap();
        let out = render_prompt(ctx_for(AgentId::Agent0), tmp.path()).unwrap();
        assert!(
            out.contains("FALLBACK POLICY"),
            "no [addendum] section should fall back to default filename"
        );
    }

    #[test]
    fn netsky_toml_addendum_absolute_path_used_as_is() {
        let tmp = tempfile::tempdir().unwrap();
        let abs_addendum = tmp.path().join("absolute-addendum.md");
        std::fs::write(&abs_addendum, "ABSOLUTE POLICY").unwrap();
        std::fs::write(
            tmp.path().join("netsky.toml"),
            format!(
                "schema_version = 1\n[addendum]\nagent0 = \"{}\"\n",
                abs_addendum.display()
            ),
        )
        .unwrap();
        let out = render_prompt(ctx_for(AgentId::Agent0), tmp.path()).unwrap();
        assert!(out.contains("ABSOLUTE POLICY"));
    }
}