// memory-search: hook binary for ambient memory retrieval
//
// Reads JSON from stdin (Claude Code UserPromptSubmit hook format),
// searches memory for relevant entries, outputs results tagged with
// an anti-injection cookie.
//
// This is a thin wrapper that delegates to the poc-memory search
// engine but formats output for the hook protocol.

use std::collections::HashSet;
use std::fs;
use std::io::{self, Read, Write};
use std::path::{Path, PathBuf};
use std::process::Command;
use std::time::{Duration, SystemTime};

fn main() {
    let mut input = String::new();
    io::stdin().read_to_string(&mut input).unwrap_or_default();

    let json: serde_json::Value = match serde_json::from_str(&input) {
        Ok(v) => v,
        Err(_) => return,
    };

    let prompt = json["prompt"].as_str().unwrap_or("");
    let session_id = json["session_id"].as_str().unwrap_or("");

    if prompt.is_empty() || session_id.is_empty() {
        return;
    }

    // Skip short prompts
    let word_count = prompt.split_whitespace().count();
    if word_count < 3 {
        return;
    }

    // Skip system/idle prompts
    for prefix in &["Kent is AFK", "You're on your own", "IRC mention"] {
        if prompt.starts_with(prefix) {
            return;
        }
    }

    // Extract search terms (strip stop words)
    let query = extract_query_terms(prompt, 3);
    if query.is_empty() {
        return;
    }

    // Run poc-memory search
    let output = Command::new("poc-memory")
        .args(["search", &query])
        .output();

    let search_output = match output {
        Ok(o) if o.status.success() => String::from_utf8_lossy(&o.stdout).to_string(),
        _ => return,
    };

    if search_output.trim().is_empty() {
        return;
    }

    // Session state for dedup
    let state_dir = PathBuf::from("/tmp/claude-memory-search");
    fs::create_dir_all(&state_dir).ok();

    // Clean up state files older than 24h (opportunistic, best-effort)
    cleanup_stale_files(&state_dir, Duration::from_secs(86400));

    let cookie = load_or_create_cookie(&state_dir, session_id);
    let seen = load_seen(&state_dir, session_id);

    // Parse search output and filter
    let mut result_output = String::new();
    let mut count = 0;
    let max_entries = 5;

    for line in search_output.lines() {
        if count >= max_entries { break; }

        // Lines starting with → or space+number are results
        let trimmed = line.trim();
        if trimmed.is_empty() { continue; }

        // Extract key from result line like "→ 1. [0.83/0.83] identity.md  (c4)"
        if let Some(key) = extract_key_from_line(trimmed) {
            if seen.contains(&key) { continue; }
            mark_seen(&state_dir, session_id, &key);
            result_output.push_str(line);
            result_output.push('\n');
            count += 1;
        } else if count > 0 {
            // Snippet line following a result
            result_output.push_str(line);
            result_output.push('\n');
        }
    }

    if count == 0 { return; }

    println!("Recalled memories [{}]:", cookie);
    print!("{}", result_output);
}

fn extract_query_terms(text: &str, max_terms: usize) -> String {
    const STOP_WORDS: &[&str] = &[
        "the", "a", "an", "is", "are", "was", "were", "do", "does", "did",
        "have", "has", "had", "will", "would", "could", "should", "can",
        "may", "might", "shall", "been", "being", "to", "of", "in", "for",
        "on", "with", "at", "by", "from", "as", "but", "or", "and", "not",
        "no", "if", "then", "than", "that", "this", "it", "its", "my",
        "your", "our", "we", "you", "i", "me", "he", "she", "they", "them",
        "what", "how", "why", "when", "where", "about", "just", "let",
        "want", "tell", "show", "think", "know", "see", "look", "make",
        "get", "go", "some", "any", "all", "very", "really", "also", "too",
        "so", "up", "out", "here", "there",
    ];

    text.to_lowercase()
        .split(|c: char| !c.is_alphanumeric())
        .filter(|w| !w.is_empty() && w.len() > 2 && !STOP_WORDS.contains(w))
        .take(max_terms)
        .collect::<Vec<_>>()
        .join(" ")
}

fn extract_key_from_line(line: &str) -> Option<String> {
    // Match lines like "→ 1. [0.83/0.83] identity.md  (c4)"
    // or "  1. [0.83/0.83] identity.md  (c4)"
    let after_bracket = line.find("] ")?;
    let rest = &line[after_bracket + 2..];
    // Key is from here until optional "  (c" or end of line
    let key_end = rest.find("  (c").unwrap_or(rest.len());
    let key = rest[..key_end].trim();
    if key.is_empty() || !key.contains('.') {
        None
    } else {
        Some(key.to_string())
    }
}

fn load_or_create_cookie(dir: &Path, session_id: &str) -> String {
    let path = dir.join(format!("cookie-{}", session_id));
    if path.exists() {
        fs::read_to_string(&path).unwrap_or_default().trim().to_string()
    } else {
        let cookie = generate_cookie();
        fs::write(&path, &cookie).ok();
        cookie
    }
}

fn generate_cookie() -> String {
    uuid::Uuid::new_v4().as_simple().to_string()[..12].to_string()
}

fn load_seen(dir: &Path, session_id: &str) -> HashSet<String> {
    let path = dir.join(format!("seen-{}", session_id));
    if path.exists() {
        fs::read_to_string(path)
            .unwrap_or_default()
            .lines()
            .map(|s| s.to_string())
            .collect()
    } else {
        HashSet::new()
    }
}

fn mark_seen(dir: &Path, session_id: &str, key: &str) {
    let path = dir.join(format!("seen-{}", session_id));
    if let Ok(mut f) = fs::OpenOptions::new().create(true).append(true).open(path) {
        writeln!(f, "{}", key).ok();
    }
}

fn cleanup_stale_files(dir: &Path, max_age: Duration) {
    let entries = match fs::read_dir(dir) {
        Ok(e) => e,
        Err(_) => return,
    };
    let cutoff = SystemTime::now() - max_age;
    for entry in entries.flatten() {
        if let Ok(meta) = entry.metadata() {
            if let Ok(modified) = meta.modified() {
                if modified < cutoff {
                    fs::remove_file(entry.path()).ok();
                }
            }
        }
    }
}