use portable_pty::{CommandBuilder, PtySize, native_pty_system};
use std::io::{BufRead, BufReader};
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use tokio::sync::watch;

use crate::llm::types::CompletionResponse;

/// Manages a Claude Code session via a pseudo-terminal.
///
/// Spawns `claude -p` in a PTY so isatty() returns true (which may
/// influence billing), while using `--output-format stream-json` to
/// get clean, structured NDJSON output instead of TUI escape sequences.
///
/// Supports session resumption: if a `session_id` is provided, passes
/// `--resume <id>` so Claude Code loads the prior conversation transcript
/// from disk and continues with full context.
pub struct ClaudeCodeProvider;

impl ClaudeCodeProvider {
    pub fn new() -> Self {
        Self
    }

    pub async fn chat_stream<F>(
        &self,
        user_message: &str,
        project_root: &str,
        session_id: Option<&str>,
        cancel_rx: &mut watch::Receiver<bool>,
        mut on_token: F,
    ) -> Result<CompletionResponse, String>
    where
        F: FnMut(&str) + Send,
    {
        let message = user_message.to_string();
        let cwd = project_root.to_string();
        let resume_id = session_id.map(|s| s.to_string());
        let cancelled = Arc::new(AtomicBool::new(false));
        let cancelled_clone = cancelled.clone();

        let mut cancel_watch = cancel_rx.clone();
        tokio::spawn(async move {
            while cancel_watch.changed().await.is_ok() {
                if *cancel_watch.borrow() {
                    cancelled_clone.store(true, Ordering::Relaxed);
                    break;
                }
            }
        });

        let (token_tx, mut token_rx) = tokio::sync::mpsc::unbounded_channel::<String>();
        let (sid_tx, sid_rx) = tokio::sync::oneshot::channel::<String>();

        let pty_handle = tokio::task::spawn_blocking(move || {
            run_pty_session(&message, &cwd, resume_id.as_deref(), cancelled, token_tx, sid_tx)
        });

        let mut full_output = String::new();
        while let Some(token) = token_rx.recv().await {
            full_output.push_str(&token);
            on_token(&token);
        }

        pty_handle
            .await
            .map_err(|e| format!("PTY task panicked: {e}"))??;

        let captured_session_id = sid_rx.await.ok();

        Ok(CompletionResponse {
            content: Some(full_output),
            tool_calls: None,
            session_id: captured_session_id,
        })
    }
}

/// Run `claude -p` with stream-json output inside a PTY.
///
/// The PTY makes isatty() return true. The `-p` flag gives us
/// single-shot non-interactive mode with structured output.
fn run_pty_session(
    user_message: &str,
    cwd: &str,
    resume_session_id: Option<&str>,
    cancelled: Arc<AtomicBool>,
    token_tx: tokio::sync::mpsc::UnboundedSender<String>,
    sid_tx: tokio::sync::oneshot::Sender<String>,
) -> Result<(), String> {
    let pty_system = native_pty_system();

    let pair = pty_system
        .openpty(PtySize {
            rows: 50,
            cols: 200,
            pixel_width: 0,
            pixel_height: 0,
        })
        .map_err(|e| format!("Failed to open PTY: {e}"))?;

    let mut cmd = CommandBuilder::new("claude");
    cmd.arg("-p");
    cmd.arg(user_message);
    if let Some(sid) = resume_session_id {
        cmd.arg("--resume");
        cmd.arg(sid);
    }
    cmd.arg("--output-format");
    cmd.arg("stream-json");
    cmd.arg("--verbose");
    cmd.cwd(cwd);
    // Keep TERM reasonable but disable color
    cmd.env("NO_COLOR", "1");
    // Allow nested spawning when the server itself runs inside Claude Code
    cmd.env("CLAUDECODE", "");

    eprintln!(
        "[pty-debug] Spawning: claude -p \"{}\" {} --output-format stream-json --verbose",
        user_message,
        resume_session_id
            .map(|s| format!("--resume {s}"))
            .unwrap_or_default()
    );

    let mut child = pair
        .slave
        .spawn_command(cmd)
        .map_err(|e| format!("Failed to spawn claude: {e}"))?;

    eprintln!(
        "[pty-debug] Process spawned, pid: {:?}",
        child.process_id()
    );
    drop(pair.slave);

    let reader = pair
        .master
        .try_clone_reader()
        .map_err(|e| format!("Failed to clone PTY reader: {e}"))?;

    // We don't need to write anything — -p mode takes prompt as arg
    drop(pair.master);

    // Read NDJSON lines from stdout
    let (line_tx, line_rx) = std::sync::mpsc::channel::<Option<String>>();

    std::thread::spawn(move || {
        let buf_reader = BufReader::new(reader);
        eprintln!("[pty-debug] Reader thread started");
        for line in buf_reader.lines() {
            match line {
                Ok(l) => {
                    eprintln!("[pty-debug] raw line: {}", l);
                    if line_tx.send(Some(l)).is_err() {
                        break;
                    }
                }
                Err(e) => {
                    eprintln!("[pty-debug] read error: {e}");
                    let _ = line_tx.send(None);
                    break;
                }
            }
        }
        eprintln!("[pty-debug] Reader thread done");
        let _ = line_tx.send(None);
    });

    let mut got_result = false;
    let mut sid_tx = Some(sid_tx);

    loop {
        if cancelled.load(Ordering::Relaxed) {
            let _ = child.kill();
            return Err("Cancelled".to_string());
        }

        match line_rx.recv_timeout(std::time::Duration::from_millis(500)) {
            Ok(Some(line)) => {
                let trimmed = line.trim();
                if trimmed.is_empty() {
                    continue;
                }

                eprintln!(
                    "[pty-debug] processing: {}...",
                    &trimmed[..trimmed.len().min(120)]
                );

                // Try to parse as JSON
                if let Ok(json) = serde_json::from_str::<serde_json::Value>(trimmed)
                    && let Some(event_type) = json.get("type").and_then(|t| t.as_str())
                {
                    // Capture session_id from any event that has it
                    if let Some(tx) = sid_tx.take() {
                        if let Some(sid) = json.get("session_id").and_then(|s| s.as_str()) {
                            let _ = tx.send(sid.to_string());
                        } else {
                            // Put it back if this event didn't have a session_id
                            sid_tx = Some(tx);
                        }
                    }

                    match event_type {
                        // Streaming deltas (when --include-partial-messages is used)
                        "stream_event" => {
                            if let Some(event) = json.get("event") {
                                handle_stream_event(event, &token_tx);
                            }
                        }
                        // Complete assistant message
                        "assistant" => {
                            if let Some(message) = json.get("message")
                                && let Some(content) =
                                    message.get("content").and_then(|c| c.as_array())
                            {
                                for block in content {
                                    if let Some(text) =
                                        block.get("text").and_then(|t| t.as_str())
                                    {
                                        let _ = token_tx.send(text.to_string());
                                    }
                                }
                            }
                        }
                        // Final result with usage stats
                        "result" => {
                            if let Some(cost) =
                                json.get("total_cost_usd").and_then(|c| c.as_f64())
                            {
                                let _ =
                                    token_tx.send(format!("\n\n---\n_Cost: ${cost:.4}_\n"));
                            }
                            if let Some(usage) = json.get("usage") {
                                let input = usage
                                    .get("input_tokens")
                                    .and_then(|t| t.as_u64())
                                    .unwrap_or(0);
                                let output = usage
                                    .get("output_tokens")
                                    .and_then(|t| t.as_u64())
                                    .unwrap_or(0);
                                let cached = usage
                                    .get("cache_read_input_tokens")
                                    .and_then(|t| t.as_u64())
                                    .unwrap_or(0);
                                let _ = token_tx.send(format!(
                                    "_Tokens: {input} in / {output} out / {cached} cached_\n"
                                ));
                            }
                            got_result = true;
                        }
                        // System init — log billing info
                        "system" => {
                            let api_source = json
                                .get("apiKeySource")
                                .and_then(|s| s.as_str())
                                .unwrap_or("unknown");
                            let model = json
                                .get("model")
                                .and_then(|s| s.as_str())
                                .unwrap_or("unknown");
                            let _ = token_tx
                                .send(format!("_[{model} | apiKey: {api_source}]_\n\n"));
                        }
                        // Rate limit info
                        "rate_limit_event" => {
                            if let Some(info) = json.get("rate_limit_info") {
                                let status = info
                                    .get("status")
                                    .and_then(|s| s.as_str())
                                    .unwrap_or("unknown");
                                let limit_type = info
                                    .get("rateLimitType")
                                    .and_then(|s| s.as_str())
                                    .unwrap_or("unknown");
                                let _ = token_tx.send(format!(
                                    "_[rate limit: {status} ({limit_type})]_\n\n"
                                ));
                            }
                        }
                        _ => {}
                    }
                }
                // Ignore non-JSON lines (terminal escape sequences)

                if got_result {
                    break;
                }
            }
            Ok(None) => break, // EOF
            Err(std::sync::mpsc::RecvTimeoutError::Timeout) => {
                // Check if child has exited
                if let Ok(Some(_status)) = child.try_wait() {
                    // Drain remaining lines
                    while let Ok(Some(line)) = line_rx.try_recv() {
                        let trimmed = line.trim();
                        if let Ok(json) = serde_json::from_str::<serde_json::Value>(trimmed)
                            && let Some(event) = json
                                .get("type")
                                .filter(|t| t.as_str() == Some("stream_event"))
                                .and_then(|_| json.get("event"))
                        {
                            handle_stream_event(event, &token_tx);
                        }
                    }
                    break;
                }
            }
            Err(std::sync::mpsc::RecvTimeoutError::Disconnected) => break,
        }

        // Don't set got_result here — just let the process finish naturally
        let _ = got_result;
    }

    // Wait briefly for Claude Code to flush its session transcript to disk.
    // The `result` event means the API response is done, but the process
    // still needs to write the conversation to the JSONL session file.
    match child.try_wait() {
        Ok(Some(_)) => {} // Already exited
        _ => {
            // Give it up to 2 seconds to exit cleanly
            for _ in 0..20 {
                std::thread::sleep(std::time::Duration::from_millis(100));
                if let Ok(Some(_)) = child.try_wait() {
                    break;
                }
            }
            // If still running after 2s, kill it
            let _ = child.kill();
        }
    }
    Ok(())
}

/// Extract text from a stream event and send to the token channel.
fn handle_stream_event(
    event: &serde_json::Value,
    token_tx: &tokio::sync::mpsc::UnboundedSender<String>,
) {
    let event_type = event.get("type").and_then(|t| t.as_str()).unwrap_or("");

    match event_type {
        // Text content streaming
        "content_block_delta" => {
            if let Some(delta) = event.get("delta") {
                let delta_type = delta.get("type").and_then(|t| t.as_str()).unwrap_or("");
                match delta_type {
                    "text_delta" => {
                        if let Some(text) = delta.get("text").and_then(|t| t.as_str()) {
                            let _ = token_tx.send(text.to_string());
                        }
                    }
                    "thinking_delta" => {
                        if let Some(thinking) =
                            delta.get("thinking").and_then(|t| t.as_str())
                        {
                            let _ = token_tx.send(format!("[thinking] {thinking}"));
                        }
                    }
                    _ => {}
                }
            }
        }
        // Message complete — log usage info
        "message_delta" => {
            if let Some(usage) = event.get("usage") {
                let output_tokens = usage
                    .get("output_tokens")
                    .and_then(|t| t.as_u64())
                    .unwrap_or(0);
                let _ = token_tx.send(format!("\n[tokens: {output_tokens} output]\n"));
            }
        }
        // Log errors
        "error" => {
            if let Some(error) = event.get("error") {
                let msg = error
                    .get("message")
                    .and_then(|m| m.as_str())
                    .unwrap_or("unknown error");
                let _ = token_tx.send(format!("\n[error: {msg}]\n"));
            }
        }
        _ => {}
    }
}