// oneshot.rs — One-shot agent execution
//
// Runs an agent definition (from agents/*.agent files) through the API:
// build prompt → call LLM with tools → return result. Agents apply
// changes via tool calls during the LLM call — no action parsing needed.
//
// This is distinct from the interactive agent loop in agent/mod.rs:
// oneshot agents run a fixed prompt sequence and exit, while the
// interactive agent has a turn loop with streaming and TUI.

use crate::store::{self, Store};
use crate::subconscious::{defs, prompts};

use std::fs;
use std::path::PathBuf;
use std::sync::atomic::{AtomicPtr, Ordering};

// Global pid path for signal handler cleanup — stored as a leaked CString
// so the signal handler can unlink it without allocation.
static PID_CPATH: AtomicPtr<libc::c_char> = AtomicPtr::new(std::ptr::null_mut());

/// RAII guard that removes the pid file on drop (normal exit, panic).
struct PidGuard;

impl Drop for PidGuard {
    fn drop(&mut self) {
        let ptr = PID_CPATH.swap(std::ptr::null_mut(), Ordering::SeqCst);
        if !ptr.is_null() {
            unsafe { libc::unlink(ptr); }
            // Reclaim the leaked CString
            unsafe { drop(std::ffi::CString::from_raw(ptr)); }
        }
    }
}

/// Register signal handlers to clean up pid file on SIGTERM/SIGINT.
fn register_pid_cleanup(pid_path: &std::path::Path) {
    let c_path = std::ffi::CString::new(pid_path.to_string_lossy().as_bytes())
        .expect("pid path contains null");
    // Leak the CString so the signal handler can access it
    let old = PID_CPATH.swap(c_path.into_raw(), Ordering::SeqCst);
    if !old.is_null() {
        unsafe { drop(std::ffi::CString::from_raw(old)); }
    }
    unsafe {
        libc::signal(libc::SIGTERM, pid_cleanup_handler as *const () as libc::sighandler_t);
        libc::signal(libc::SIGINT, pid_cleanup_handler as *const () as libc::sighandler_t);
    }
}

extern "C" fn pid_cleanup_handler(sig: libc::c_int) {
    let ptr = PID_CPATH.swap(std::ptr::null_mut(), Ordering::SeqCst);
    if !ptr.is_null() {
        unsafe { libc::unlink(ptr); }
        // Don't free — we're in a signal handler, just leak it
    }
    unsafe {
        libc::signal(sig, libc::SIG_DFL);
        libc::raise(sig);
    }
}

// ---------------------------------------------------------------------------
// Agent execution
// ---------------------------------------------------------------------------

/// Result of running a single agent.
pub struct AgentResult {
    pub output: String,
    pub node_keys: Vec<String>,
    /// Directory containing output() files from the agent run.
    pub state_dir: std::path::PathBuf,
}

/// Run a single agent and return the result (no action application — tools handle that).
pub fn run_and_apply(
    store: &mut Store,
    agent_name: &str,
    batch_size: usize,
    llm_tag: &str,
) -> Result<(), String> {
    run_and_apply_with_log(store, agent_name, batch_size, llm_tag, &|_| {})
}

pub fn run_and_apply_with_log(
    store: &mut Store,
    agent_name: &str,
    batch_size: usize,
    llm_tag: &str,
    log: &(dyn Fn(&str) + Sync),
) -> Result<(), String> {
    run_and_apply_excluded(store, agent_name, batch_size, llm_tag, log, &Default::default())
}

/// Like run_and_apply_with_log but with an in-flight exclusion set.
pub fn run_and_apply_excluded(
    store: &mut Store,
    agent_name: &str,
    batch_size: usize,
    llm_tag: &str,
    log: &(dyn Fn(&str) + Sync),
    exclude: &std::collections::HashSet<String>,
) -> Result<(), String> {
    let _result = run_one_agent_excluded(store, agent_name, batch_size, llm_tag, log, exclude)?;
    Ok(())
}

/// Run an agent with explicit target keys, bypassing the agent's query.
pub fn run_one_agent_with_keys(
    store: &mut Store,
    agent_name: &str,
    keys: &[String],
    count: usize,
    llm_tag: &str,
    log: &(dyn Fn(&str) + Sync),
) -> Result<AgentResult, String> {
    let def = defs::get_def(agent_name)
        .ok_or_else(|| format!("no .agent file for {}", agent_name))?;

    let (state_dir, pid_path, _guard) = setup_agent_state(agent_name, &def)?;

    log(&format!("targeting: {}", keys.join(", ")));
    let graph = store.build_graph();
    let mut resolved_steps = Vec::new();
    let mut all_keys: Vec<String> = keys.to_vec();
    for step in &def.steps {
        let (prompt, extra_keys) = defs::resolve_placeholders(
            &step.prompt, store, &graph, keys, count,
        );
        all_keys.extend(extra_keys);
        resolved_steps.push(prompts::ResolvedStep {
            prompt,
            phase: step.phase.clone(),
        });
    }
    let agent_batch = prompts::AgentBatch { steps: resolved_steps, node_keys: all_keys };

    // Record visits eagerly so concurrent agents pick different seeds
    if !agent_batch.node_keys.is_empty() {
        store.record_agent_visits(&agent_batch.node_keys, agent_name).ok();
    }

    run_one_agent_inner(store, agent_name, &def, agent_batch, state_dir, pid_path, llm_tag, log)
}

pub fn run_one_agent(
    store: &mut Store,
    agent_name: &str,
    batch_size: usize,
    llm_tag: &str,
    log: &(dyn Fn(&str) + Sync),
) -> Result<AgentResult, String> {
    run_one_agent_excluded(store, agent_name, batch_size, llm_tag, log, &Default::default())
}

/// Like run_one_agent but excludes nodes currently being worked on by other agents.
pub fn run_one_agent_excluded(
    store: &mut Store,
    agent_name: &str,
    batch_size: usize,
    llm_tag: &str,
    log: &(dyn Fn(&str) + Sync),
    exclude: &std::collections::HashSet<String>,
) -> Result<AgentResult, String> {
    let def = defs::get_def(agent_name)
        .ok_or_else(|| format!("no .agent file for {}", agent_name))?;

    // Set up output dir and write pid file BEFORE prompt building
    let (state_dir, pid_path, _guard) = setup_agent_state(agent_name, &def)?;

    log("building prompt");
    let effective_count = def.count.unwrap_or(batch_size);
    let agent_batch = defs::run_agent(store, &def, effective_count, exclude)?;

    run_one_agent_inner(store, agent_name, &def, agent_batch, state_dir, pid_path, llm_tag, log)
}

/// Set up agent state dir, write initial pid file, register cleanup handlers.
/// Returns (state_dir, pid_path, guard). The guard removes the pid file on drop.
fn setup_agent_state(
    agent_name: &str,
    def: &defs::AgentDef,
) -> Result<(PathBuf, PathBuf, PidGuard), String> {
    let state_dir = std::env::var("POC_AGENT_OUTPUT_DIR")
        .map(PathBuf::from)
        .unwrap_or_else(|_| store::memory_dir().join("agent-output").join(agent_name));
    fs::create_dir_all(&state_dir)
        .map_err(|e| format!("create state dir: {}", e))?;
    unsafe { std::env::set_var("POC_AGENT_OUTPUT_DIR", &state_dir); }

    // Clean up stale pid files from dead processes
    scan_pid_files(&state_dir, 0);

    let pid = std::process::id();
    let pid_path = state_dir.join(format!("pid-{}", pid));
    let first_phase = def.steps.first()
        .map(|s| s.phase.as_str())
        .unwrap_or("step-0");
    fs::write(&pid_path, first_phase).ok();

    // Register for cleanup on signals and normal exit
    register_pid_cleanup(&pid_path);

    Ok((state_dir, pid_path, PidGuard))
}

/// Check for live agent processes in a state dir. Returns (phase, pid) pairs.
/// Cleans up stale pid files and kills timed-out processes.
pub fn scan_pid_files(state_dir: &std::path::Path, timeout_secs: u64) -> Vec<(String, u32)> {
    let mut live = Vec::new();
    let Ok(entries) = fs::read_dir(state_dir) else { return live };
    for entry in entries.flatten() {
        let name = entry.file_name();
        let name_str = name.to_string_lossy();
        if !name_str.starts_with("pid-") { continue; }
        let pid: u32 = name_str.strip_prefix("pid-")
            .and_then(|s| s.parse().ok())
            .unwrap_or(0);
        if pid == 0 { continue; }

        if unsafe { libc::kill(pid as i32, 0) } != 0 {
            fs::remove_file(entry.path()).ok();
            continue;
        }

        if timeout_secs > 0 {
            if let Ok(meta) = entry.metadata() {
                if let Ok(modified) = meta.modified() {
                    if modified.elapsed().unwrap_or_default().as_secs() > timeout_secs {
                        unsafe { libc::kill(pid as i32, libc::SIGTERM); }
                        fs::remove_file(entry.path()).ok();
                        continue;
                    }
                }
            }
        }

        let phase = fs::read_to_string(entry.path())
            .unwrap_or_default()
            .trim().to_string();
        live.push((phase, pid));
    }
    live
}

/// Spawn an agent asynchronously. Writes the pid file before returning
/// so the caller immediately sees the agent as running.
pub struct SpawnResult {
    pub child: std::process::Child,
    pub log_path: PathBuf,
}

pub fn spawn_agent(
    agent_name: &str,
    state_dir: &std::path::Path,
    session_id: &str,
) -> Option<SpawnResult> {
    let def = defs::get_def(agent_name)?;
    let first_phase = def.steps.first()
        .map(|s| s.phase.as_str())
        .unwrap_or("step-0");

    let log_dir = dirs::home_dir().unwrap_or_default()
        .join(format!(".consciousness/logs/{}", agent_name));
    fs::create_dir_all(&log_dir).ok();
    let log_path = log_dir.join(format!("{}.log", store::compact_timestamp()));
    let agent_log = fs::File::create(&log_path)
        .unwrap_or_else(|_| fs::File::create("/dev/null").unwrap());

    let child = std::process::Command::new("poc-memory")
        .args(["agent", "run", agent_name, "--count", "1", "--local",
               "--state-dir", &state_dir.to_string_lossy()])
        .env("POC_SESSION_ID", session_id)
        .stdout(agent_log.try_clone().unwrap_or_else(|_| fs::File::create("/dev/null").unwrap()))
        .stderr(agent_log)
        .spawn()
        .ok()?;

    let pid = child.id();
    let pid_path = state_dir.join(format!("pid-{}", pid));
    fs::write(&pid_path, first_phase).ok();
    Some(SpawnResult { child, log_path })
}

fn run_one_agent_inner(
    _store: &mut Store,
    agent_name: &str,
    def: &defs::AgentDef,
    agent_batch: prompts::AgentBatch,
    state_dir: std::path::PathBuf,
    pid_path: std::path::PathBuf,
    _llm_tag: &str,
    log: &(dyn Fn(&str) + Sync),
) -> Result<AgentResult, String> {
    // Filter tools based on agent def specification
    let all_tools = super::tools::memory_and_journal_tools();
    let effective_tools: Vec<super::tools::Tool> = if def.tools.is_empty() {
        all_tools.to_vec()
    } else {
        all_tools.into_iter()
            .filter(|t| def.tools.iter().any(|w| w == &t.name))
            .collect()
    };
    let tools_desc = effective_tools.iter().map(|t| t.name).collect::<Vec<_>>().join(", ");
    let n_steps = agent_batch.steps.len();

    for key in &agent_batch.node_keys {
        log(&format!("  node: {}", key));
    }

    // Guard: reject oversized first prompt (later steps grow via conversation)
    let max_prompt_bytes = 800_000;
    let first_len = agent_batch.steps[0].prompt.len();
    if first_len > max_prompt_bytes {
        let prompt_kb = first_len / 1024;
        let oversize_dir = store::memory_dir().join("llm-logs").join("oversized");
        fs::create_dir_all(&oversize_dir).ok();
        let oversize_path = oversize_dir.join(format!("{}-{}.txt",
            agent_name, store::compact_timestamp()));
        let header = format!("=== OVERSIZED PROMPT ===\nagent: {}\nsize: {}KB (max {}KB)\nnodes: {:?}\n\n",
            agent_name, prompt_kb, max_prompt_bytes / 1024, agent_batch.node_keys);
        fs::write(&oversize_path, format!("{}{}", header, &agent_batch.steps[0].prompt)).ok();
        log(&format!("oversized prompt logged to {}", oversize_path.display()));
        return Err(format!(
            "prompt too large: {}KB (max {}KB) — seed nodes may be oversized",
            prompt_kb, max_prompt_bytes / 1024,
        ));
    }

    let write_pid = |phase: &str| {
        fs::write(&pid_path, phase).ok();
    };

    let phases: Vec<&str> = agent_batch.steps.iter().map(|s| s.phase.as_str()).collect();
    log(&format!("{} step(s) {:?}, {}KB initial, {}, {} nodes, output={}",
        n_steps, phases, first_len / 1024, tools_desc,
        agent_batch.node_keys.len(), state_dir.display()));

    let prompts: Vec<String> = agent_batch.steps.iter()
        .map(|s| s.prompt.clone()).collect();
    let step_phases: Vec<String> = agent_batch.steps.iter()
        .map(|s| s.phase.clone()).collect();
    let step_phases_for_bail = step_phases.clone();

    if std::env::var("POC_AGENT_VERBOSE").is_ok() {
        for (i, s) in agent_batch.steps.iter().enumerate() {
            log(&format!("=== PROMPT {}/{} ({}) ===\n\n{}", i + 1, n_steps, s.phase, s.prompt));
        }
    }
    log("\n=== CALLING LLM ===");

    // Bail check: if the agent defines a bail script, run it between steps.
    // The script receives the pid file path as $1, cwd = state dir.
    let bail_script = def.bail.as_ref().map(|name| {
        let agents_dir = defs::agents_dir();
        agents_dir.join(name)
    });
    let state_dir_for_bail = state_dir.clone();
    let pid_path_for_bail = pid_path.clone();
    let bail_fn = move |step_idx: usize| -> Result<(), String> {
        // Update phase in pid file and provenance tracking
        if step_idx < step_phases_for_bail.len() {
            write_pid(&step_phases_for_bail[step_idx]);
        }
        // Run bail script if defined
        if let Some(ref script) = bail_script {
            let status = std::process::Command::new(script)
                .arg(&pid_path_for_bail)
                .current_dir(&state_dir_for_bail)
                .status()
                .map_err(|e| format!("bail script {:?} failed: {}", script, e))?;
            if !status.success() {
                return Err(format!("bailed at step {}: {:?} exited {}",
                    step_idx + 1, script.file_name().unwrap_or_default(),
                    status.code().unwrap_or(-1)));
            }
        }
        Ok(())
    };

    let output = crate::subconscious::api::call_api_with_tools_sync(
        agent_name, &prompts, &step_phases, def.temperature, def.priority,
        &effective_tools, Some(&bail_fn), log)?;

    Ok(AgentResult {
        output,
        node_keys: agent_batch.node_keys,
        state_dir,
    })
}