truth-mirror 0.2.0

//! Ground-truth constraints and conversation-trajectory context fed into review.
//!
//! Ground truth = inviolable constraints discovered from `TRUTH.md`/`AGENTS.md`/
//! `CLAUDE.md` at any nested level plus OpenSpec specs. Trajectory = a bounded
//! window of recent user/agent messages so the reviewer judges direction, not
//! just the isolated diff.

use std::{
    fs,
    path::{Path, PathBuf},
};

use anyhow::{Context, Result};
use serde::Deserialize;

use crate::config::{GroundTruthConfig, HistoryConfig};

/// Directories never walked for ground-truth files.
const SKIP_DIRS: &[&str] = &[".git", "target", "node_modules", ".truth-mirror"];

/// Collect ground-truth constraints from the repo, shallowest (repo-root) first,
/// bounded by `max_bytes`. Deterministic ordering (by depth then path) for tests.
pub fn collect_ground_truth(repo_root: &Path, config: &GroundTruthConfig) -> Result<String> {
    if !config.enabled {
        return Ok(String::new());
    }

    let mut hits: Vec<(usize, PathBuf)> = Vec::new();
    collect_files(repo_root, repo_root, config, 0, &mut hits)?;
    // Shallowest first, then lexicographic — root AGENTS.md/TRUTH.md win the budget.
    hits.sort_by(|(depth_a, path_a), (depth_b, path_b)| {
        depth_a.cmp(depth_b).then_with(|| path_a.cmp(path_b))
    });

    let mut out = String::new();
    for (_, path) in hits {
        let rel = path.strip_prefix(repo_root).unwrap_or(&path);
        let body = match fs::read_to_string(&path) {
            Ok(body) => body,
            Err(_) => continue,
        };
        let section = format!("### {}\n{}\n\n", rel.display(), body.trim());
        if out.len() + section.len() > config.max_bytes {
            let remaining = config.max_bytes.saturating_sub(out.len());
            out.push_str(&truncate_on_char_boundary(&section, remaining));
            break;
        }
        out.push_str(&section);
    }

    Ok(out.trim_end().to_owned())
}

fn collect_files(
    repo_root: &Path,
    dir: &Path,
    config: &GroundTruthConfig,
    depth: usize,
    hits: &mut Vec<(usize, PathBuf)>,
) -> Result<()> {
    let entries = match fs::read_dir(dir) {
        Ok(entries) => entries,
        Err(_) => return Ok(()),
    };

    for entry in entries.flatten() {
        let path = entry.path();
        let name = entry.file_name().to_string_lossy().into_owned();
        let file_type = match entry.file_type() {
            Ok(file_type) => file_type,
            Err(_) => continue,
        };

        if file_type.is_dir() {
            if SKIP_DIRS.contains(&name.as_str()) {
                continue;
            }
            collect_files(repo_root, &path, config, depth + 1, hits)?;
        } else if is_ground_truth_file(repo_root, &path, &name, config) {
            hits.push((depth, path));
        }
    }

    Ok(())
}

fn is_ground_truth_file(
    repo_root: &Path,
    path: &Path,
    name: &str,
    config: &GroundTruthConfig,
) -> bool {
    if config.file_names.iter().any(|wanted| wanted == name) {
        return true;
    }

    if config.include_openspec_specs
        && name.ends_with(".md")
        && let Ok(rel) = path.strip_prefix(repo_root)
    {
        let rel = rel.to_string_lossy();
        return rel.starts_with("openspec/specs/");
    }

    false
}

#[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq)]
#[serde(rename_all = "lowercase")]
pub enum Role {
    User,
    Agent,
}

#[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
pub struct TranscriptMessage {
    pub role: Role,
    pub text: String,
}

/// Yields recent conversation messages (oldest-first).
pub trait TrajectoryProvider {
    fn messages(&self) -> Result<Vec<TranscriptMessage>>;
}

/// Reads a `{"role":"user|agent","text":"..."}`-per-line transcript.
#[derive(Clone, Debug)]
pub struct JsonlTranscriptProvider {
    pub path: PathBuf,
}

impl TrajectoryProvider for JsonlTranscriptProvider {
    fn messages(&self) -> Result<Vec<TranscriptMessage>> {
        let contents = match fs::read_to_string(&self.path) {
            Ok(contents) => contents,
            Err(error) if error.kind() == std::io::ErrorKind::NotFound => return Ok(Vec::new()),
            Err(error) => {
                return Err(error)
                    .with_context(|| format!("reading transcript {}", self.path.display()));
            }
        };

        contents
            .lines()
            .filter(|line| !line.trim().is_empty())
            .map(|line| {
                serde_json::from_str::<TranscriptMessage>(line)
                    .with_context(|| "parsing transcript line".to_string())
            })
            .collect()
    }
}

/// Recent commit subjects as agent messages — a universal trajectory proxy when
/// no explicit transcript is configured.
#[derive(Clone, Debug)]
pub struct GitLogProvider {
    pub repo_root: PathBuf,
    pub count: usize,
}

impl TrajectoryProvider for GitLogProvider {
    fn messages(&self) -> Result<Vec<TranscriptMessage>> {
        let output = std::process::Command::new("git")
            .arg("-C")
            .arg(&self.repo_root)
            .args(["log", &format!("-n{}", self.count), "--format=%s"])
            .output()
            .context("running git log for trajectory")?;
        if !output.status.success() {
            return Ok(Vec::new());
        }
        let text = String::from_utf8_lossy(&output.stdout);
        // git log is newest-first; reverse to oldest-first for chronological order.
        let mut messages: Vec<TranscriptMessage> = text
            .lines()
            .filter(|line| !line.trim().is_empty())
            .map(|line| TranscriptMessage {
                role: Role::Agent,
                text: format!("committed: {}", line.trim()),
            })
            .collect();
        messages.reverse();
        Ok(messages)
    }
}

/// Pick a trajectory provider: the configured JSONL transcript if present, else
/// recent commits.
pub fn trajectory_provider(
    repo_root: &Path,
    history: &HistoryConfig,
) -> Box<dyn TrajectoryProvider> {
    if let Some(rel) = &history.transcript_path {
        let path = repo_root.join(rel);
        if path.is_file() {
            return Box::new(JsonlTranscriptProvider { path });
        }
    }
    Box::new(GitLogProvider {
        repo_root: repo_root.to_path_buf(),
        count: history.window_user + history.window_agent + 5,
    })
}

/// Keep the last `window_user` user messages and last `window_agent` agent
/// messages, preserving chronological order, then trim oldest to `max_bytes`.
pub fn window_trajectory(
    messages: &[TranscriptMessage],
    window_user: usize,
    window_agent: usize,
    max_bytes: usize,
) -> Vec<TranscriptMessage> {
    let mut users = 0;
    let mut agents = 0;
    let mut kept: Vec<TranscriptMessage> = Vec::new();

    for message in messages.iter().rev() {
        let keep = match message.role {
            Role::User if users < window_user => {
                users += 1;
                true
            }
            Role::Agent if agents < window_agent => {
                agents += 1;
                true
            }
            _ => false,
        };
        if keep {
            kept.push(message.clone());
        }
    }
    kept.reverse();

    // Byte budget: drop oldest until under budget.
    let mut total: usize = kept.iter().map(|message| message.text.len()).sum();
    let mut start = 0;
    while start < kept.len() && total > max_bytes {
        total -= kept[start].text.len();
        start += 1;
    }
    kept[start..].to_vec()
}

pub fn render_trajectory(messages: &[TranscriptMessage]) -> String {
    if messages.is_empty() {
        return String::new();
    }
    let mut out = String::new();
    for message in messages {
        let who = match message.role {
            Role::User => "USER",
            Role::Agent => "AGENT",
        };
        out.push_str(&format!("{who}: {}\n", message.text.trim()));
    }
    out.trim_end().to_owned()
}

/// Build the combined review-context block (constraints + trajectory).
pub fn build_review_context(
    repo_root: &Path,
    ground_truth: &GroundTruthConfig,
    history: &HistoryConfig,
    provider: Option<&dyn TrajectoryProvider>,
) -> Result<String> {
    let mut out = String::new();

    let constraints = collect_ground_truth(repo_root, ground_truth)?;
    if !constraints.is_empty() {
        out.push_str(
            "INVIOLABLE CONSTRAINTS (ground truth — a change that violates these is a REJECT):\n",
        );
        out.push_str(&constraints);
        out.push_str("\n\n");
    }

    if let Some(provider) = provider {
        let messages = provider.messages()?;
        let windowed = window_trajectory(
            &messages,
            history.window_user,
            history.window_agent,
            history.max_bytes,
        );
        let rendered = render_trajectory(&windowed);
        if !rendered.is_empty() {
            out.push_str("RECENT TRAJECTORY (judge the direction of work, not just this diff):\n");
            out.push_str(&rendered);
            out.push_str("\n\n");
        }
    }

    Ok(out.trim_end().to_owned())
}

fn truncate_on_char_boundary(value: &str, max: usize) -> String {
    if value.len() <= max {
        return value.to_owned();
    }
    let mut end = max;
    while end > 0 && !value.is_char_boundary(end) {
        end -= 1;
    }
    value[..end].to_owned()
}

#[cfg(test)]
mod tests {
    use super::{
        JsonlTranscriptProvider, Role, TrajectoryProvider, TranscriptMessage, build_review_context,
        collect_ground_truth, render_trajectory, window_trajectory,
    };
    use crate::config::{GroundTruthConfig, HistoryConfig};

    fn msg(role: Role, text: &str) -> TranscriptMessage {
        TranscriptMessage {
            role,
            text: text.to_owned(),
        }
    }

    #[test]
    fn collects_nested_constraint_files() {
        let temp = tempfile::tempdir().unwrap();
        let root = temp.path();
        std::fs::write(root.join("AGENTS.md"), "root agents").unwrap();
        std::fs::create_dir_all(root.join("sub/dir")).unwrap();
        std::fs::write(root.join("sub/dir/TRUTH.md"), "nested truth").unwrap();
        std::fs::create_dir_all(root.join("openspec/specs/x")).unwrap();
        std::fs::write(root.join("openspec/specs/x/spec.md"), "a spec").unwrap();
        // Ignored: unrelated file and skip dir.
        std::fs::write(root.join("README.md"), "readme").unwrap();
        std::fs::create_dir_all(root.join(".git")).unwrap();
        std::fs::write(root.join(".git/AGENTS.md"), "should be skipped").unwrap();

        let out = collect_ground_truth(root, &GroundTruthConfig::default()).unwrap();

        assert!(out.contains("root agents"));
        assert!(out.contains("nested truth"));
        assert!(out.contains("a spec"));
        assert!(!out.contains("readme"));
        assert!(!out.contains("should be skipped"));
    }

    #[test]
    fn ground_truth_respects_byte_budget() {
        let temp = tempfile::tempdir().unwrap();
        std::fs::write(temp.path().join("AGENTS.md"), "x".repeat(1000)).unwrap();
        let config = GroundTruthConfig {
            max_bytes: 100,
            ..GroundTruthConfig::default()
        };

        let out = collect_ground_truth(temp.path(), &config).unwrap();

        assert!(out.len() <= 100, "got {} bytes", out.len());
    }

    #[test]
    fn disabled_ground_truth_returns_empty() {
        let temp = tempfile::tempdir().unwrap();
        std::fs::write(temp.path().join("TRUTH.md"), "constraints").unwrap();
        let config = GroundTruthConfig {
            enabled: false,
            ..GroundTruthConfig::default()
        };

        assert!(
            collect_ground_truth(temp.path(), &config)
                .unwrap()
                .is_empty()
        );
    }

    #[test]
    fn window_keeps_last_n_and_m_in_order() {
        let messages = vec![
            msg(Role::User, "u1"),
            msg(Role::Agent, "a1"),
            msg(Role::Agent, "a2"),
            msg(Role::User, "u2"),
            msg(Role::Agent, "a3"),
            msg(Role::User, "u3"),
        ];

        let windowed = window_trajectory(&messages, 2, 2, 10_000);

        // last 2 users (u2,u3), last 2 agents (a2,a3), chronological.
        let texts: Vec<&str> = windowed.iter().map(|m| m.text.as_str()).collect();
        assert_eq!(texts, ["a2", "u2", "a3", "u3"]);
    }

    #[test]
    fn window_never_exceeds_limits() {
        let mut messages = Vec::new();
        for i in 0..50 {
            messages.push(msg(Role::User, &format!("u{i}")));
            messages.push(msg(Role::Agent, &format!("a{i}")));
        }

        let windowed = window_trajectory(&messages, 3, 5, 10_000);

        let users = windowed.iter().filter(|m| m.role == Role::User).count();
        let agents = windowed.iter().filter(|m| m.role == Role::Agent).count();
        assert!(users <= 3);
        assert!(agents <= 5);
    }

    #[test]
    fn jsonl_provider_reads_messages() {
        let temp = tempfile::tempdir().unwrap();
        let path = temp.path().join("t.jsonl");
        std::fs::write(
            &path,
            "{\"role\":\"user\",\"text\":\"do X\"}\n{\"role\":\"agent\",\"text\":\"did Y\"}\n",
        )
        .unwrap();

        let provider = JsonlTranscriptProvider { path };
        let messages = provider.messages().unwrap();

        assert_eq!(messages.len(), 2);
        assert_eq!(messages[0].role, Role::User);
        assert_eq!(messages[1].text, "did Y");
    }

    #[test]
    fn build_context_includes_constraints_and_trajectory() {
        let temp = tempfile::tempdir().unwrap();
        std::fs::write(temp.path().join("TRUTH.md"), "never fake tests").unwrap();
        let transcript = temp.path().join("t.jsonl");
        std::fs::write(
            &transcript,
            "{\"role\":\"user\",\"text\":\"add feature\"}\n",
        )
        .unwrap();
        let provider = JsonlTranscriptProvider { path: transcript };

        let out = build_review_context(
            temp.path(),
            &GroundTruthConfig::default(),
            &HistoryConfig::default(),
            Some(&provider),
        )
        .unwrap();

        assert!(out.contains("INVIOLABLE CONSTRAINTS"));
        assert!(out.contains("never fake tests"));
        assert!(out.contains("RECENT TRAJECTORY"));
        assert!(out.contains("add feature"));
    }

    #[test]
    fn render_trajectory_is_empty_for_no_messages() {
        assert!(render_trajectory(&[]).is_empty());
    }
}