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::{FunctionCall, Message, Role, ToolCall};

/// Result from a Claude Code session containing structured messages.
pub struct ClaudeCodeResult {
    /// The conversation messages produced by Claude Code, including assistant
    /// turns (with optional tool_calls) and tool result turns.
    pub messages: Vec<Message>,
    /// Session ID for conversation resumption on subsequent requests.
    pub session_id: Option<String>,
}

/// 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<ClaudeCodeResult, 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 (msg_tx, msg_rx) = std::sync::mpsc::channel::<Message>();
        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,
                msg_tx,
                sid_tx,
            )
        });

        while let Some(token) = token_rx.recv().await {
            on_token(&token);
        }

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

        let captured_session_id = sid_rx.await.ok();
        let structured_messages: Vec<Message> = msg_rx.try_iter().collect();

        Ok(ClaudeCodeResult {
            messages: structured_messages,
            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.
///
/// Sends streaming text tokens via `token_tx` for real-time display, and
/// complete structured `Message` values via `msg_tx` for the final message
/// history (assistant turns with tool_calls, and tool result turns).
fn run_pty_session(
    user_message: &str,
    cwd: &str,
    resume_session_id: Option<&str>,
    cancelled: Arc<AtomicBool>,
    token_tx: tokio::sync::mpsc::UnboundedSender<String>,
    msg_tx: std::sync::mpsc::Sender<Message>,
    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 — used for real-time text display only
                        "stream_event" => {
                            if let Some(event) = json.get("event") {
                                handle_stream_event(event, &token_tx);
                            }
                        }
                        // Complete assistant message — extract text and tool_use blocks
                        "assistant" => {
                            if let Some(message) = json.get("message")
                                && let Some(content) =
                                    message.get("content").and_then(|c| c.as_array())
                            {
                                parse_assistant_message(content, &msg_tx);
                            }
                        }
                        // User message containing tool results from Claude Code's own execution
                        "user" => {
                            if let Some(message) = json.get("message")
                                && let Some(content) =
                                    message.get("content").and_then(|c| c.as_array())
                            {
                                parse_tool_results(content, &msg_tx);
                            }
                        }
                        // Final result with usage stats
                        "result" => {
                            got_result = true;
                        }
                        // System init — log billing info via streaming display
                        "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 — surface briefly in streaming display
                        "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_type) =
                                json.get("type").and_then(|t| t.as_str())
                        {
                            match event_type {
                                "stream_event" => {
                                    if let Some(event) = json.get("event") {
                                        handle_stream_event(event, &token_tx);
                                    }
                                }
                                "assistant" => {
                                    if let Some(message) = json.get("message")
                                        && let Some(content) = message
                                            .get("content")
                                            .and_then(|c| c.as_array())
                                    {
                                        parse_assistant_message(content, &msg_tx);
                                    }
                                }
                                "user" => {
                                    if let Some(message) = json.get("message")
                                        && let Some(content) = message
                                            .get("content")
                                            .and_then(|c| c.as_array())
                                    {
                                        parse_tool_results(content, &msg_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(())
}

/// Parse a complete `assistant` message content array.
///
/// Extracts text blocks into `content` and tool_use blocks into `tool_calls`,
/// then sends a single `Message { role: Assistant }` via `msg_tx`.
/// This is the authoritative source for the final message structure — streaming
/// text deltas (via `handle_stream_event`) are only used for the live display.
fn parse_assistant_message(
    content: &[serde_json::Value],
    msg_tx: &std::sync::mpsc::Sender<Message>,
) {
    let mut text = String::new();
    let mut tool_calls: Vec<ToolCall> = Vec::new();

    for block in content {
        match block.get("type").and_then(|t| t.as_str()) {
            Some("text") => {
                if let Some(t) = block.get("text").and_then(|t| t.as_str()) {
                    text.push_str(t);
                }
            }
            Some("tool_use") => {
                let id = block
                    .get("id")
                    .and_then(|v| v.as_str())
                    .map(|s| s.to_string());
                let name = block
                    .get("name")
                    .and_then(|v| v.as_str())
                    .unwrap_or("")
                    .to_string();
                let input = block
                    .get("input")
                    .cloned()
                    .unwrap_or(serde_json::Value::Object(serde_json::Map::new()));
                let arguments = serde_json::to_string(&input).unwrap_or_default();
                tool_calls.push(ToolCall {
                    id,
                    function: FunctionCall { name, arguments },
                    kind: "function".to_string(),
                });
            }
            _ => {}
        }
    }

    let msg = Message {
        role: Role::Assistant,
        content: text,
        tool_calls: if tool_calls.is_empty() {
            None
        } else {
            Some(tool_calls)
        },
        tool_call_id: None,
    };
    let _ = msg_tx.send(msg);
}

/// Parse a `user` message containing tool_result blocks.
///
/// Claude Code injects tool results into the conversation as `user` role
/// messages. Each `tool_result` block becomes a separate `Message { role: Tool }`.
fn parse_tool_results(
    content: &[serde_json::Value],
    msg_tx: &std::sync::mpsc::Sender<Message>,
) {
    for block in content {
        if block.get("type").and_then(|t| t.as_str()) != Some("tool_result") {
            continue;
        }

        let tool_use_id = block
            .get("tool_use_id")
            .and_then(|v| v.as_str())
            .map(|s| s.to_string());

        // `content` in a tool_result can be a plain string or an array of content blocks
        let content_str = match block.get("content") {
            Some(serde_json::Value::String(s)) => s.clone(),
            Some(serde_json::Value::Array(arr)) => {
                // Extract text from content block array
                arr.iter()
                    .filter_map(|b| {
                        if b.get("type").and_then(|t| t.as_str()) == Some("text") {
                            b.get("text").and_then(|t| t.as_str()).map(|s| s.to_string())
                        } else {
                            None
                        }
                    })
                    .collect::<Vec<_>>()
                    .join("\n")
            }
            Some(other) => serde_json::to_string(other).unwrap_or_default(),
            None => String::new(),
        };

        let _ = msg_tx.send(Message {
            role: Role::Tool,
            content: content_str,
            tool_calls: None,
            tool_call_id: tool_use_id,
        });
    }
}

/// Extract text from a stream event and send to the token channel for live display.
///
/// Stream events provide incremental text deltas for real-time rendering.
/// The authoritative final message content comes from complete `assistant` events.
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 — only text_delta, not input_json_delta (tool args)
        "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}"));
                        }
                    }
                    _ => {}
                }
            }
        }
        // Log errors via streaming display
        "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"));
            }
        }
        _ => {}
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;

    fn collect_messages(
        f: impl Fn(&std::sync::mpsc::Sender<Message>),
    ) -> Vec<Message> {
        let (tx, rx) = std::sync::mpsc::channel();
        f(&tx);
        drop(tx);
        rx.try_iter().collect()
    }

    #[test]
    fn parse_assistant_message_text_only() {
        let content = vec![json!({"type": "text", "text": "Hello, world!"})];
        let msgs = collect_messages(|tx| parse_assistant_message(&content, tx));
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].role, Role::Assistant);
        assert_eq!(msgs[0].content, "Hello, world!");
        assert!(msgs[0].tool_calls.is_none());
    }

    #[test]
    fn parse_assistant_message_with_tool_use() {
        let content = vec![
            json!({"type": "text", "text": "I'll read that file."}),
            json!({
                "type": "tool_use",
                "id": "toolu_abc123",
                "name": "Read",
                "input": {"file_path": "/src/main.rs"}
            }),
        ];
        let msgs = collect_messages(|tx| parse_assistant_message(&content, tx));
        assert_eq!(msgs.len(), 1);
        let msg = &msgs[0];
        assert_eq!(msg.role, Role::Assistant);
        assert_eq!(msg.content, "I'll read that file.");
        let tool_calls = msg.tool_calls.as_ref().expect("should have tool calls");
        assert_eq!(tool_calls.len(), 1);
        assert_eq!(tool_calls[0].id.as_deref(), Some("toolu_abc123"));
        assert_eq!(tool_calls[0].function.name, "Read");
        let args: serde_json::Value =
            serde_json::from_str(&tool_calls[0].function.arguments).unwrap();
        assert_eq!(args["file_path"], "/src/main.rs");
    }

    #[test]
    fn parse_assistant_message_multiple_tool_uses() {
        let content = vec![
            json!({"type": "tool_use", "id": "id1", "name": "Glob", "input": {"pattern": "*.rs"}}),
            json!({"type": "tool_use", "id": "id2", "name": "Bash", "input": {"command": "cargo test"}}),
        ];
        let msgs = collect_messages(|tx| parse_assistant_message(&content, tx));
        assert_eq!(msgs.len(), 1);
        let tool_calls = msgs[0].tool_calls.as_ref().unwrap();
        assert_eq!(tool_calls.len(), 2);
        assert_eq!(tool_calls[0].function.name, "Glob");
        assert_eq!(tool_calls[1].function.name, "Bash");
    }

    #[test]
    fn parse_tool_results_string_content() {
        let content = vec![json!({
            "type": "tool_result",
            "tool_use_id": "toolu_abc123",
            "content": "fn main() { println!(\"hello\"); }"
        })];
        let msgs = collect_messages(|tx| parse_tool_results(&content, tx));
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].role, Role::Tool);
        assert_eq!(msgs[0].content, "fn main() { println!(\"hello\"); }");
        assert_eq!(msgs[0].tool_call_id.as_deref(), Some("toolu_abc123"));
    }

    #[test]
    fn parse_tool_results_array_content() {
        let content = vec![json!({
            "type": "tool_result",
            "tool_use_id": "toolu_xyz",
            "content": [
                {"type": "text", "text": "Line 1"},
                {"type": "text", "text": "Line 2"}
            ]
        })];
        let msgs = collect_messages(|tx| parse_tool_results(&content, tx));
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].content, "Line 1\nLine 2");
        assert_eq!(msgs[0].tool_call_id.as_deref(), Some("toolu_xyz"));
    }

    #[test]
    fn parse_tool_results_multiple_results() {
        let content = vec![
            json!({"type": "tool_result", "tool_use_id": "id1", "content": "result1"}),
            json!({"type": "tool_result", "tool_use_id": "id2", "content": "result2"}),
        ];
        let msgs = collect_messages(|tx| parse_tool_results(&content, tx));
        assert_eq!(msgs.len(), 2);
        assert_eq!(msgs[0].tool_call_id.as_deref(), Some("id1"));
        assert_eq!(msgs[1].tool_call_id.as_deref(), Some("id2"));
    }

    #[test]
    fn parse_tool_results_ignores_non_tool_result_blocks() {
        let content = vec![
            json!({"type": "text", "text": "not a tool result"}),
            json!({"type": "tool_result", "tool_use_id": "id1", "content": "actual result"}),
        ];
        let msgs = collect_messages(|tx| parse_tool_results(&content, tx));
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].tool_call_id.as_deref(), Some("id1"));
    }

    #[test]
    fn parse_assistant_message_empty_text_with_tool_use() {
        // When a message has only tool_use (no text), content should be empty string
        let content = vec![json!({
            "type": "tool_use",
            "id": "toolu_1",
            "name": "Write",
            "input": {"file_path": "foo.rs", "content": "fn foo() {}"}
        })];
        let msgs = collect_messages(|tx| parse_assistant_message(&content, tx));
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].content, "");
        assert!(msgs[0].tool_calls.is_some());
    }

    #[test]
    fn handle_stream_event_text_delta_sends_token() {
        let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel();
        let event = json!({
            "type": "content_block_delta",
            "delta": {"type": "text_delta", "text": "hello "}
        });
        handle_stream_event(&event, &tx);
        drop(tx);
        let tokens: Vec<_> = {
            let mut v = vec![];
            while let Ok(t) = rx.try_recv() {
                v.push(t);
            }
            v
        };
        assert_eq!(tokens, vec!["hello "]);
    }

    #[test]
    fn handle_stream_event_input_json_delta_not_sent() {
        // Tool argument JSON deltas should NOT be sent as text tokens
        let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel();
        let event = json!({
            "type": "content_block_delta",
            "delta": {"type": "input_json_delta", "partial_json": "{\"path\":"}
        });
        handle_stream_event(&event, &tx);
        drop(tx);
        let tokens: Vec<String> = {
            let mut v = vec![];
            while let Ok(t) = rx.try_recv() {
                v.push(t);
            }
            v
        };
        assert!(tokens.is_empty());
    }
}