// memory-search: combined hook for session context loading + ambient memory retrieval
//
// Modes:
//   --hook     Run as Claude Code UserPromptSubmit hook (reads stdin, injects into conversation)
//   --debug    Replay last stashed input, dump every stage to stdout
//   --seen     Show the seen set for current session
//   (default)  No-op (future: manual search modes)

use clap::Parser;
use poc_memory::search::{self, AlgoStage};
use poc_memory::store;
use std::collections::{BTreeMap, HashSet};
use std::fs;
use std::io::{self, Read, Write};
use std::path::{Path, PathBuf};
use std::process::Command;
use std::time::{Duration, SystemTime};

#[derive(Parser)]
#[command(name = "memory-search")]
struct Args {
    /// Run as Claude Code hook (reads stdin, outputs for injection)
    #[arg(long)]
    hook: bool,

    /// Debug mode: replay last stashed input, dump every stage
    #[arg(short, long)]
    debug: bool,

    /// Show the seen set and returned memories for this session
    #[arg(long)]
    seen: bool,

    /// Show full seen set (list all keys)
    #[arg(long)]
    seen_full: bool,

    /// Max results to return
    #[arg(long, default_value = "5")]
    max_results: usize,

    /// Algorithm pipeline stages: e.g. spread spectral,k=20 spread,max_hops=4
    /// Default: spread.
    pipeline: Vec<String>,
}

const STASH_PATH: &str = "/tmp/claude-memory-search/last-input.json";
/// Max bytes per context chunk (hook output limit is ~10K chars)
const CHUNK_SIZE: usize = 9000;

fn main() {
    // Daemon agent calls set POC_AGENT=1 — skip memory search.
    if std::env::var("POC_AGENT").is_ok() {
        return;
    }

    let args = Args::parse();

    if args.seen || args.seen_full {
        show_seen();
        return;
    }

    let input = if args.hook {
        // Hook mode: read from stdin, stash for later debug runs
        let mut buf = String::new();
        io::stdin().read_to_string(&mut buf).unwrap_or_default();
        fs::create_dir_all("/tmp/claude-memory-search").ok();
        fs::write(STASH_PATH, &buf).ok();
        buf
    } else {
        // All other modes: replay stashed input
        fs::read_to_string(STASH_PATH).unwrap_or_else(|_| {
            eprintln!("No stashed input at {}", STASH_PATH);
            std::process::exit(1);
        })
    };

    let debug = args.debug || !args.hook;

    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 session_id.is_empty() {
        return;
    }

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

    // Detect post-compaction reload via mmap backward scan
    let transcript_path = json["transcript_path"].as_str().unwrap_or("");
    let is_compaction = poc_memory::transcript::detect_new_compaction(
        &state_dir, session_id, transcript_path,
    );

    // First prompt or post-compaction: load full context
    let cookie_path = state_dir.join(format!("cookie-{}", session_id));
    let is_first = !cookie_path.exists();

    if is_first || is_compaction {
        // Reset seen set to keys that load-context will inject
        let seen_path = state_dir.join(format!("seen-{}", session_id));
        fs::remove_file(&seen_path).ok();
    }

    if debug {
        println!("[memory-search] session={} is_first={} is_compaction={}", session_id, is_first, is_compaction);
    }

    if is_first || is_compaction {
        // Create/touch the cookie
        let cookie = if is_first {
            let c = generate_cookie();
            fs::write(&cookie_path, &c).ok();
            c
        } else {
            fs::read_to_string(&cookie_path).unwrap_or_default().trim().to_string()
        };

        if debug { println!("[memory-search] loading full context"); }

        // Load full memory context, chunk it, print first chunk, save rest
        if let Ok(output) = Command::new("poc-memory").args(["load-context"]).output() {
            if output.status.success() {
                let ctx = String::from_utf8_lossy(&output.stdout).to_string();
                if !ctx.trim().is_empty() {
                    // Extract keys from all chunks for seen set
                    for line in ctx.lines() {
                        if line.starts_with("--- ") && line.ends_with(" ---") {
                            let inner = &line[4..line.len() - 4];
                            if let Some(paren) = inner.rfind(" (") {
                                let key = inner[..paren].trim();
                                mark_seen(&state_dir, session_id, key);
                            }
                        }
                    }

                    let chunks = chunk_context(&ctx, CHUNK_SIZE);
                    if debug {
                        println!("[memory-search] context: {} bytes, {} chunks",
                            ctx.len(), chunks.len());
                    }

                    // Print first chunk
                    if let Some(first) = chunks.first() {
                        if args.hook {
                            print!("{}", first);
                        }
                    }

                    // Save remaining chunks for drip-feeding
                    save_pending_chunks(&state_dir, session_id, &chunks[1..]);
                }
            }
        }

        let _ = cookie;
    } else {
        // Not first call: drip-feed next pending chunk
        if let Some(chunk) = pop_pending_chunk(&state_dir, session_id) {
            if debug {
                println!("[memory-search] drip-feeding pending chunk: {} bytes", chunk.len());
            }
            if args.hook {
                print!("{}", chunk);
            }
        }
    }

    // Search requires a prompt (PostToolUse events don't have one)
    if prompt.is_empty() {
        return;
    }

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

    let store = match store::Store::load() {
        Ok(s) => s,
        Err(_) => return,
    };

    // Search for node keys in last ~150k tokens of transcript
    if debug { println!("[memory-search] transcript: {}", transcript_path); }
    let mut terms = extract_weighted_terms(transcript_path, 150_000, &store);

    // Also extract terms from the prompt itself (handles fresh sessions
    // and queries about topics not yet mentioned in the transcript)
    let prompt_terms = search::extract_query_terms(prompt, 8);
    if !prompt_terms.is_empty() {
        if debug { println!("[memory-search] prompt terms: {}", prompt_terms); }
        for word in prompt_terms.split_whitespace() {
            let lower = word.to_lowercase();
            // Prompt terms get weight 1.0 (same as direct mention)
            terms.entry(lower).or_insert(1.0);
        }
    }

    if debug {
        println!("[memory-search] {} terms total", terms.len());
        let mut by_weight: Vec<_> = terms.iter().collect();
        by_weight.sort_by(|a, b| b.1.total_cmp(a.1));
        for (term, weight) in by_weight.iter().take(20) {
            println!("  {:.3}  {}", weight, term);
        }
    }

    if terms.is_empty() {
        if debug { println!("[memory-search] no terms found, done"); }
        return;
    }

    // Parse algorithm pipeline
    let pipeline: Vec<AlgoStage> = if args.pipeline.is_empty() {
        // Default: just spreading activation
        vec![AlgoStage::parse("spread").unwrap()]
    } else {
        let mut stages = Vec::new();
        for arg in &args.pipeline {
            match AlgoStage::parse(arg) {
                Ok(s) => stages.push(s),
                Err(e) => {
                    eprintln!("error: {}", e);
                    std::process::exit(1);
                }
            }
        }
        stages
    };

    if debug {
        let names: Vec<String> = pipeline.iter().map(|s| format!("{}", s.algo)).collect();
        println!("[memory-search] pipeline: {}", names.join(" → "));
    }

    // Extract seeds from terms
    let graph = poc_memory::graph::build_graph_fast(&store);
    let (seeds, direct_hits) = search::match_seeds(&terms, &store);

    if seeds.is_empty() {
        if debug { println!("[memory-search] no seeds matched, done"); }
        return;
    }

    if debug {
        println!("[memory-search] {} seeds", seeds.len());
        let mut sorted = seeds.clone();
        sorted.sort_by(|a, b| b.1.total_cmp(&a.1));
        for (key, score) in sorted.iter().take(20) {
            println!("  {:.4}  {}", score, key);
        }
    }

    let max_results = if debug { args.max_results.max(25) } else { args.max_results };
    let raw_results = search::run_pipeline(&pipeline, seeds, &graph, &store, debug, max_results);

    let results: Vec<search::SearchResult> = raw_results.into_iter()
        .map(|(key, activation)| {
            let is_direct = direct_hits.contains(&key);
            search::SearchResult { key, activation, is_direct, snippet: None }
        }).collect();

    if debug {
        println!("[memory-search] {} search results", results.len());
        for r in results.iter().take(10) {
            let marker = if r.is_direct { "→" } else { " " };
            println!("  {} [{:.4}] {}", marker, r.activation, r.key);
        }
    }

    if results.is_empty() {
        if debug { println!("[memory-search] no results, done"); }
        return;
    }

    let seen = load_seen(&state_dir, session_id);
    if debug { println!("[memory-search] {} keys in seen set", seen.len()); }

    // Format results like poc-memory search output
    let search_output = search::format_results(&results);

    let cookie = fs::read_to_string(&cookie_path).unwrap_or_default().trim().to_string();

    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; }

        let trimmed = line.trim();
        if trimmed.is_empty() { continue; }

        if let Some(key) = extract_key_from_line(trimmed) {
            if seen.contains(&key) { continue; }
            mark_seen(&state_dir, session_id, &key);
            mark_returned(&state_dir, session_id, &key);
            result_output.push_str(line);
            result_output.push('\n');
            count += 1;
        } else if count > 0 {
            result_output.push_str(line);
            result_output.push('\n');
        }
    }

    if count == 0 {
        if debug { println!("[memory-search] all results already seen"); }
        return;
    }

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

    // Clean up stale state files (opportunistic)
    cleanup_stale_files(&state_dir, Duration::from_secs(86400));
}


/// Split context output into chunks of approximately `max_bytes`, breaking
/// at section boundaries ("--- KEY (group) ---" lines).
fn chunk_context(ctx: &str, max_bytes: usize) -> Vec<String> {
    // Split into sections at group boundaries, then merge small adjacent
    // sections into chunks up to max_bytes.
    let mut sections: Vec<String> = Vec::new();
    let mut current = String::new();

    for line in ctx.lines() {
        // Group headers start new sections
        if line.starts_with("--- ") && line.ends_with(" ---") && !current.is_empty() {
            sections.push(std::mem::take(&mut current));
        }
        if !current.is_empty() {
            current.push('\n');
        }
        current.push_str(line);
    }
    if !current.is_empty() {
        sections.push(current);
    }

    // Merge small sections into chunks, respecting max_bytes
    let mut chunks: Vec<String> = Vec::new();
    let mut chunk = String::new();
    for section in sections {
        if !chunk.is_empty() && chunk.len() + section.len() + 1 > max_bytes {
            chunks.push(std::mem::take(&mut chunk));
        }
        if !chunk.is_empty() {
            chunk.push('\n');
        }
        chunk.push_str(&section);
    }
    if !chunk.is_empty() {
        chunks.push(chunk);
    }
    chunks
}

/// Save remaining chunks to disk for drip-feeding on subsequent hook calls.
fn save_pending_chunks(dir: &Path, session_id: &str, chunks: &[String]) {
    let chunks_dir = dir.join(format!("chunks-{}", session_id));
    // Clear any old chunks
    let _ = fs::remove_dir_all(&chunks_dir);
    if chunks.is_empty() { return; }
    fs::create_dir_all(&chunks_dir).ok();
    for (i, chunk) in chunks.iter().enumerate() {
        let path = chunks_dir.join(format!("{:04}", i));
        fs::write(path, chunk).ok();
    }
}

/// Pop the next pending chunk (lowest numbered file). Returns None if no chunks remain.
fn pop_pending_chunk(dir: &Path, session_id: &str) -> Option<String> {
    let chunks_dir = dir.join(format!("chunks-{}", session_id));
    if !chunks_dir.exists() { return None; }

    let mut entries: Vec<_> = fs::read_dir(&chunks_dir).ok()?
        .flatten()
        .filter(|e| e.file_type().map(|t| t.is_file()).unwrap_or(false))
        .collect();
    entries.sort_by_key(|e| e.file_name());

    let first = entries.first()?;
    let content = fs::read_to_string(first.path()).ok()?;
    fs::remove_file(first.path()).ok();

    // Clean up directory if empty
    if fs::read_dir(&chunks_dir).ok().map(|mut d| d.next().is_none()).unwrap_or(true) {
        fs::remove_dir(&chunks_dir).ok();
    }

    Some(content)
}

/// Reverse-scan the transcript JSONL, extracting text from user/assistant
/// messages until we accumulate `max_tokens` tokens of text content.
/// Then search for all node keys as substrings, weighted by position.
fn extract_weighted_terms(
    path: &str,
    max_tokens: usize,
    store: &poc_memory::store::Store,
) -> BTreeMap<String, f64> {
    if path.is_empty() { return BTreeMap::new(); }

    let content = match fs::read_to_string(path) {
        Ok(c) => c,
        Err(_) => return BTreeMap::new(),
    };

    // Collect text from messages, scanning backwards, until token budget hit
    let mut message_texts: Vec<String> = Vec::new();
    let mut token_count = 0;

    for line in content.lines().rev() {
        if token_count >= max_tokens { break; }

        let obj: serde_json::Value = match serde_json::from_str(line) {
            Ok(v) => v,
            Err(_) => continue,
        };

        let msg_type = obj.get("type").and_then(|v| v.as_str()).unwrap_or("");
        if msg_type != "user" && msg_type != "assistant" { continue; }

        let mut msg_text = String::new();
        let msg = obj.get("message").unwrap_or(&obj);
        match msg.get("content") {
            Some(serde_json::Value::String(s)) => {
                msg_text.push_str(s);
            }
            Some(serde_json::Value::Array(arr)) => {
                for block in arr {
                    if block.get("type").and_then(|v| v.as_str()) == Some("text") {
                        if let Some(t) = block.get("text").and_then(|v| v.as_str()) {
                            msg_text.push(' ');
                            msg_text.push_str(t);
                        }
                    }
                }
            }
            _ => {}
        }

        token_count += msg_text.len() / 4;
        message_texts.push(msg_text);
    }

    // Reverse so oldest is first (position weighting: later = more recent = higher)
    message_texts.reverse();
    let all_text = message_texts.join(" ").to_lowercase();
    let text_len = all_text.len();
    if text_len == 0 { return BTreeMap::new(); }

    // Search for each node key as a substring (casefolded), accumulate position-weighted score
    let mut terms = BTreeMap::new();
    for (key, _node) in &store.nodes {
        let key_folded = key.to_lowercase();
        let mut pos = 0;
        while let Some(found) = all_text[pos..].find(&key_folded) {
            let abs_pos = pos + found;
            let weight = (abs_pos + 1) as f64 / text_len as f64;
            *terms.entry(key_folded.clone()).or_insert(0.0) += weight;
            pos = abs_pos + key_folded.len();
        }
    }

    terms
}


fn extract_key_from_line(line: &str) -> Option<String> {
    let after_bracket = line.find("] ")?;
    let rest = &line[after_bracket + 2..];
    let key_end = rest.find("  (c").unwrap_or(rest.len());
    let key = rest[..key_end].trim();
    if key.is_empty() {
        None
    } else {
        Some(key.to_string())
    }
}

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

/// Parse a seen-file line: "TIMESTAMP\tKEY" or legacy "KEY"
fn parse_seen_line(line: &str) -> &str {
    line.split_once('\t').map(|(_, key)| key).unwrap_or(line)
}

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()
            .filter(|s| !s.is_empty())
            .map(|s| parse_seen_line(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) {
        let ts = chrono::Local::now().format("%Y-%m-%dT%H:%M:%S");
        writeln!(f, "{}\t{}", ts, key).ok();
    }
}

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

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

fn show_seen() {
    let state_dir = PathBuf::from("/tmp/claude-memory-search");

    // Read stashed input for session_id
    let input = match fs::read_to_string(STASH_PATH) {
        Ok(s) => s,
        Err(_) => {
            eprintln!("No stashed input at {}", STASH_PATH);
            return;
        }
    };
    let json: serde_json::Value = match serde_json::from_str(&input) {
        Ok(v) => v,
        Err(_) => {
            eprintln!("Failed to parse stashed input");
            return;
        }
    };
    let session_id = json["session_id"].as_str().unwrap_or("");
    if session_id.is_empty() {
        eprintln!("No session_id in stashed input");
        return;
    }

    println!("Session: {}", session_id);

    let cookie_path = state_dir.join(format!("cookie-{}", session_id));
    if let Ok(cookie) = fs::read_to_string(&cookie_path) {
        println!("Cookie: {}", cookie.trim());
    }

    let returned = load_returned(&state_dir, session_id);
    if !returned.is_empty() {
        println!("\nReturned by search ({}):", returned.len());
        for key in &returned {
            println!("  {}", key);
        }
    }

    // Read seen file in insertion order (append-only file)
    let seen_path = state_dir.join(format!("seen-{}", session_id));
    let seen_lines: Vec<String> = fs::read_to_string(&seen_path)
        .unwrap_or_default()
        .lines()
        .filter(|s| !s.is_empty())
        .map(|s| s.to_string())
        .collect();
    let returned_set: HashSet<_> = returned.iter().cloned().collect();
    let pre_seeded = seen_lines.len().saturating_sub(returned.len());
    println!("\nSeen set ({} total, {} pre-seeded):", seen_lines.len(), pre_seeded);

    if Args::parse().seen_full {
        for line in &seen_lines {
            let key = parse_seen_line(line);
            let marker = if returned_set.contains(key) { "→ " } else { "  " };
            // Show timestamp if present, otherwise just key
            if let Some((ts, k)) = line.split_once('\t') {
                println!("  {} {}{}", ts, marker, k);
            } else {
                println!("  (no ts) {}{}", marker, line);
            }
        }
    }
}

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();
                }
            }
        }
    }
}