use std::collections::BTreeMap;
use std::io::{self, BufRead, Write};
use std::path::{Path, PathBuf};
use std::process::Command;

use libmcp::{Generation, SurfaceKind};
use serde::Deserialize;
use serde_json::{Value, json};
use thiserror::Error;
use uuid::Uuid;

use crate::mcp::fault::{FaultRecord, FaultStage};
use crate::mcp::output::{
    ToolOutput, fallback_detailed_tool_output, split_presentation, tool_success,
};
use crate::mcp::protocol::{
    CLAUDE_BIN_ENV, CLAUDE_CONSULT_PREFIX, CLAUDE_EFFORT, CLAUDE_MODEL, CLAUDE_TOOLSET,
    EMPTY_MCP_CONFIG,
};

pub(crate) fn run_worker(generation: u64) -> Result<(), Box<dyn std::error::Error>> {
    let generation = generation_from_wire(generation);
    let stdin = io::stdin();
    let mut stdout = io::stdout().lock();
    let mut service = WorkerService::new(generation);

    for line in stdin.lock().lines() {
        let line = line?;
        if line.trim().is_empty() {
            continue;
        }
        let request = serde_json::from_str::<crate::mcp::protocol::WorkerRequest>(&line)?;
        let response = match request {
            crate::mcp::protocol::WorkerRequest::Execute { id, operation } => {
                let outcome = match service.execute(operation) {
                    Ok(result) => crate::mcp::protocol::WorkerOutcome::Success { result },
                    Err(fault) => crate::mcp::protocol::WorkerOutcome::Fault { fault },
                };
                crate::mcp::protocol::WorkerResponse { id, outcome }
            }
        };
        serde_json::to_writer(&mut stdout, &response)?;
        stdout.write_all(b"\n")?;
        stdout.flush()?;
    }

    Ok(())
}

struct WorkerService {
    generation: Generation,
}

impl WorkerService {
    fn new(generation: Generation) -> Self {
        Self { generation }
    }

    fn execute(
        &mut self,
        operation: crate::mcp::protocol::WorkerOperation,
    ) -> Result<Value, FaultRecord> {
        match operation {
            crate::mcp::protocol::WorkerOperation::CallTool { name, arguments } => {
                self.call_tool(&name, arguments)
            }
        }
    }

    fn call_tool(&mut self, name: &str, arguments: Value) -> Result<Value, FaultRecord> {
        let operation = format!("tools/call:{name}");
        let (presentation, arguments) =
            split_presentation(arguments, &operation, self.generation, FaultStage::Worker)?;
        let output = match name {
            "consult" => {
                let args = deserialize::<ConsultArgs>(arguments, &operation, self.generation)?;
                let request = ConsultRequest::parse(args)
                    .map_err(|error| invalid_consult_request(self.generation, &operation, error))?;
                let response = invoke_claude(&request)
                    .map_err(|error| consult_fault(self.generation, &operation, error))?;
                consult_output(&request, &response, self.generation, &operation)?
            }
            other => {
                return Err(FaultRecord::invalid_input(
                    self.generation,
                    FaultStage::Worker,
                    &operation,
                    format!("unknown worker tool `{other}`"),
                ));
            }
        };
        tool_success(
            output,
            presentation,
            self.generation,
            FaultStage::Worker,
            &operation,
        )
    }
}

#[derive(Debug, Deserialize)]
struct ConsultArgs {
    prompt: String,
    cwd: Option<String>,
    max_turns: Option<u64>,
    session_id: Option<String>,
}

#[derive(Debug, Clone)]
struct ConsultRequest {
    prompt: PromptText,
    cwd: WorkingDirectory,
    max_turns: Option<TurnLimit>,
    session: Option<SessionHandle>,
}

impl ConsultRequest {
    fn parse(args: ConsultArgs) -> Result<Self, ConsultRequestError> {
        Ok(Self {
            prompt: PromptText::parse(args.prompt)?,
            cwd: WorkingDirectory::resolve(args.cwd)?,
            max_turns: args.max_turns.map(TurnLimit::parse).transpose()?,
            session: args.session_id.map(SessionHandle::parse).transpose()?,
        })
    }

    fn session_mode(&self) -> &'static str {
        if self.session.is_some() {
            "resumed"
        } else {
            "new"
        }
    }

    fn requested_session_id(&self) -> Option<String> {
        self.session.as_ref().map(SessionHandle::display)
    }
}

#[derive(Debug, Clone)]
struct PromptText {
    original: String,
    rendered: String,
}

impl PromptText {
    fn parse(raw: String) -> Result<Self, ConsultRequestError> {
        if raw.trim().is_empty() {
            return Err(ConsultRequestError::EmptyPrompt);
        }
        Ok(Self {
            rendered: format!("{CLAUDE_CONSULT_PREFIX}\n\n{raw}"),
            original: raw,
        })
    }

    fn as_str(&self) -> &str {
        self.original.as_str()
    }

    fn rendered(&self) -> &str {
        self.rendered.as_str()
    }
}

#[derive(Debug, Clone)]
struct WorkingDirectory(PathBuf);

impl WorkingDirectory {
    fn resolve(raw: Option<String>) -> Result<Self, ConsultRequestError> {
        let base =
            std::env::current_dir().map_err(|source| ConsultRequestError::CurrentDir { source })?;
        let requested = raw.map_or_else(|| base.clone(), PathBuf::from);
        let candidate = if requested.is_absolute() {
            requested
        } else {
            base.join(requested)
        };
        let canonical =
            candidate
                .canonicalize()
                .map_err(|source| ConsultRequestError::Canonicalize {
                    path: candidate.display().to_string(),
                    source,
                })?;
        if !canonical.is_dir() {
            return Err(ConsultRequestError::NotDirectory(
                canonical.display().to_string(),
            ));
        }
        Ok(Self(canonical))
    }

    fn as_path(&self) -> &Path {
        self.0.as_path()
    }

    fn display(&self) -> String {
        self.0.display().to_string()
    }
}

#[derive(Debug, Clone, Copy)]
struct TurnLimit(u64);

impl TurnLimit {
    fn parse(raw: u64) -> Result<Self, ConsultRequestError> {
        if raw == 0 {
            return Err(ConsultRequestError::InvalidTurnLimit);
        }
        Ok(Self(raw))
    }

    fn get(self) -> u64 {
        self.0
    }
}

#[derive(Debug, Clone)]
struct SessionHandle(Uuid);

impl SessionHandle {
    fn parse(raw: String) -> Result<Self, ConsultRequestError> {
        Uuid::parse_str(&raw)
            .map(Self)
            .map_err(|_| ConsultRequestError::InvalidSessionHandle(raw))
    }

    fn display(&self) -> String {
        self.0.to_string()
    }
}

#[derive(Debug, Error)]
enum ConsultRequestError {
    #[error("prompt must not be empty")]
    EmptyPrompt,
    #[error("failed to resolve the current working directory: {source}")]
    CurrentDir { source: io::Error },
    #[error("failed to resolve working directory `{path}`: {source}")]
    Canonicalize { path: String, source: io::Error },
    #[error("working directory `{0}` is not a directory")]
    NotDirectory(String),
    #[error("max_turns must be greater than zero")]
    InvalidTurnLimit,
    #[error("session_id must be a valid UUID, got `{0}`")]
    InvalidSessionHandle(String),
}

#[derive(Debug, Error)]
enum ConsultInvocationError {
    #[error("failed to spawn Claude Code: {0}")]
    Spawn(#[source] io::Error),
    #[error("Claude Code returned non-JSON output: {0}")]
    InvalidJson(String),
    #[error("{0}")]
    Downstream(String),
}

#[derive(Debug, Deserialize)]
struct ClaudeJsonEnvelope {
    #[serde(rename = "type")]
    envelope_type: String,
    subtype: Option<String>,
    is_error: bool,
    duration_ms: Option<u64>,
    duration_api_ms: Option<u64>,
    num_turns: Option<u64>,
    result: Option<String>,
    stop_reason: Option<String>,
    session_id: Option<String>,
    total_cost_usd: Option<f64>,
    usage: Option<Value>,
    #[serde(rename = "modelUsage")]
    model_usage: Option<Value>,
    #[serde(default)]
    permission_denials: Vec<Value>,
    fast_mode_state: Option<String>,
    uuid: Option<String>,
}

#[derive(Debug)]
struct ConsultResponse {
    cwd: WorkingDirectory,
    result: String,
    duration_ms: u64,
    duration_api_ms: Option<u64>,
    num_turns: u64,
    stop_reason: Option<String>,
    session_id: Option<String>,
    total_cost_usd: Option<f64>,
    usage: Option<Value>,
    model_usage: Option<Value>,
    permission_denials: Vec<Value>,
    fast_mode_state: Option<String>,
    uuid: Option<String>,
}

impl ConsultResponse {
    fn model_name(&self) -> Option<String> {
        let Value::Object(models) = self.model_usage.as_ref()? else {
            return None;
        };
        models.keys().next().cloned()
    }
}

fn deserialize<T: for<'de> Deserialize<'de>>(
    value: Value,
    operation: &str,
    generation: Generation,
) -> Result<T, FaultRecord> {
    serde_json::from_value(value).map_err(|error| {
        FaultRecord::invalid_input(
            generation,
            FaultStage::Protocol,
            operation,
            format!("invalid params: {error}"),
        )
    })
}

fn invalid_consult_request(
    generation: Generation,
    operation: &str,
    error: ConsultRequestError,
) -> FaultRecord {
    FaultRecord::invalid_input(generation, FaultStage::Worker, operation, error.to_string())
}

fn consult_fault(
    generation: Generation,
    operation: &str,
    error: ConsultInvocationError,
) -> FaultRecord {
    match error {
        ConsultInvocationError::Spawn(source) => FaultRecord::process(
            generation,
            FaultStage::Claude,
            operation,
            source.to_string(),
        ),
        ConsultInvocationError::InvalidJson(detail)
        | ConsultInvocationError::Downstream(detail) => {
            FaultRecord::downstream(generation, FaultStage::Claude, operation, detail)
        }
    }
}

fn invoke_claude(request: &ConsultRequest) -> Result<ConsultResponse, ConsultInvocationError> {
    let mut command = Command::new(claude_binary());
    let _ = command
        .arg("-p")
        .arg("--output-format")
        .arg("json")
        .arg("--strict-mcp-config")
        .arg("--mcp-config")
        .arg(EMPTY_MCP_CONFIG)
        .arg("--disable-slash-commands")
        .arg("--no-chrome")
        .arg("--model")
        .arg(CLAUDE_MODEL)
        .arg("--effort")
        .arg(CLAUDE_EFFORT)
        .arg("--tools")
        .arg(CLAUDE_TOOLSET)
        .arg("--permission-mode")
        .arg("dontAsk");
    if let Some(session) = request.session.as_ref() {
        let _ = command.arg("--resume").arg(session.display());
    }
    if let Some(max_turns) = request.max_turns {
        let _ = command.arg("--max-turns").arg(max_turns.get().to_string());
    }
    let output = command
        .current_dir(request.cwd.as_path())
        .arg(request.prompt.rendered())
        .output()
        .map_err(ConsultInvocationError::Spawn)?;
    let stdout = String::from_utf8_lossy(&output.stdout).trim().to_owned();
    let stderr = String::from_utf8_lossy(&output.stderr).trim().to_owned();
    let envelope = match serde_json::from_slice::<ClaudeJsonEnvelope>(&output.stdout) {
        Ok(envelope) => envelope,
        Err(_error) if !output.status.success() => {
            return Err(ConsultInvocationError::Downstream(downstream_message(
                output.status.code(),
                &stdout,
                &stderr,
            )));
        }
        Err(error) => {
            return Err(ConsultInvocationError::InvalidJson(format!(
                "{error}; stdout={stdout}; stderr={stderr}"
            )));
        }
    };
    if envelope.envelope_type != "result" {
        return Err(ConsultInvocationError::Downstream(format!(
            "unexpected Claude envelope type `{}`",
            envelope.envelope_type
        )));
    }
    if !output.status.success()
        || envelope.is_error
        || envelope.subtype.as_deref() != Some("success")
    {
        return Err(ConsultInvocationError::Downstream(
            envelope
                .result
                .filter(|value| !value.trim().is_empty())
                .unwrap_or_else(|| downstream_message(output.status.code(), &stdout, &stderr)),
        ));
    }
    Ok(ConsultResponse {
        cwd: request.cwd.clone(),
        result: envelope.result.unwrap_or_default(),
        duration_ms: envelope.duration_ms.unwrap_or(0),
        duration_api_ms: envelope.duration_api_ms,
        num_turns: envelope.num_turns.unwrap_or(0),
        stop_reason: envelope.stop_reason,
        session_id: envelope.session_id,
        total_cost_usd: envelope.total_cost_usd,
        usage: envelope.usage,
        model_usage: envelope.model_usage,
        permission_denials: envelope.permission_denials,
        fast_mode_state: envelope.fast_mode_state,
        uuid: envelope.uuid,
    })
}

fn downstream_message(status_code: Option<i32>, stdout: &str, stderr: &str) -> String {
    if !stderr.is_empty() {
        return stderr.to_owned();
    }
    if !stdout.is_empty() {
        return stdout.to_owned();
    }
    format!("Claude Code exited with status {status_code:?}")
}

fn claude_binary() -> PathBuf {
    std::env::var_os(CLAUDE_BIN_ENV)
        .map(PathBuf::from)
        .unwrap_or_else(|| PathBuf::from("claude"))
}

fn consult_output(
    request: &ConsultRequest,
    response: &ConsultResponse,
    generation: Generation,
    operation: &str,
) -> Result<ToolOutput, FaultRecord> {
    let concise = json!({
        "response": response.result,
        "cwd": response.cwd.display(),
        "session_mode": request.session_mode(),
        "requested_session_id": request.requested_session_id(),
        "prompt_prefix_injected": true,
        "model": response.model_name(),
        "duration_ms": response.duration_ms,
        "num_turns": response.num_turns,
        "stop_reason": response.stop_reason,
        "session_id": response.session_id,
        "total_cost_usd": response.total_cost_usd,
        "permission_denial_count": response.permission_denials.len(),
    });
    let full = json!({
        "response": response.result,
        "cwd": response.cwd.display(),
        "prompt": request.prompt.as_str(),
        "prompt_prefix": CLAUDE_CONSULT_PREFIX,
        "effective_prompt": request.prompt.rendered(),
        "max_turns": request.max_turns.map(TurnLimit::get),
        "session_mode": request.session_mode(),
        "requested_session_id": request.requested_session_id(),
        "duration_ms": response.duration_ms,
        "duration_api_ms": response.duration_api_ms,
        "num_turns": response.num_turns,
        "stop_reason": response.stop_reason,
        "session_id": response.session_id,
        "total_cost_usd": response.total_cost_usd,
        "usage": response.usage,
        "model_usage": response.model_usage,
        "permission_denials": response.permission_denials,
        "fast_mode_state": response.fast_mode_state,
        "uuid": response.uuid,
    });
    fallback_detailed_tool_output(
        &concise,
        &full,
        concise_text(request, response),
        Some(full_text(request, response)),
        SurfaceKind::Read,
        generation,
        FaultStage::Worker,
        operation,
    )
}

fn concise_text(request: &ConsultRequest, response: &ConsultResponse) -> String {
    let mut status = vec![
        "consult ok".to_owned(),
        format!("session={}", request.session_mode()),
        format!("turns={}", response.num_turns),
        format!("duration={}", render_duration_ms(response.duration_ms)),
    ];
    if let Some(model) = response.model_name() {
        status.push(format!("model={model}"));
    }
    if let Some(stop_reason) = response.stop_reason.as_deref() {
        status.push(format!("stop={stop_reason}"));
    }
    if let Some(cost) = response.total_cost_usd {
        status.push(format!("cost=${cost:.6}"));
    }

    let mut lines = vec![status.join(" ")];
    lines.push(format!("cwd: {}", response.cwd.display()));
    if let Some(session_id) = request.requested_session_id() {
        lines.push(format!("requested_session: {session_id}"));
    }
    if let Some(session_id) = response.session_id.as_deref() {
        lines.push(format!("session: {session_id}"));
    }
    if !response.permission_denials.is_empty() {
        lines.push(format!(
            "permission_denials: {}",
            response.permission_denials.len()
        ));
    }
    lines.push("response:".to_owned());
    lines.push(response.result.clone());
    lines.join("\n")
}

fn full_text(request: &ConsultRequest, response: &ConsultResponse) -> String {
    let mut lines = vec![
        format!(
            "consult ok session={} turns={}",
            request.session_mode(),
            response.num_turns
        ),
        format!("cwd: {}", response.cwd.display()),
        format!("duration: {}", render_duration_ms(response.duration_ms)),
    ];
    if let Some(session_id) = request.requested_session_id() {
        lines.push(format!("requested_session: {session_id}"));
    }
    if let Some(duration_api_ms) = response.duration_api_ms {
        lines.push(format!(
            "api_duration: {}",
            render_duration_ms(duration_api_ms)
        ));
    }
    if let Some(model) = response.model_name() {
        lines.push(format!("model: {model}"));
    }
    if let Some(stop_reason) = response.stop_reason.as_deref() {
        lines.push(format!("stop: {stop_reason}"));
    }
    if let Some(session_id) = response.session_id.as_deref() {
        lines.push(format!("session: {session_id}"));
    }
    if let Some(cost) = response.total_cost_usd {
        lines.push(format!("cost_usd: {cost:.6}"));
    }
    lines.push(format!(
        "permission_denials: {}",
        response.permission_denials.len()
    ));
    if let Some(fast_mode_state) = response.fast_mode_state.as_deref() {
        lines.push(format!("fast_mode: {fast_mode_state}"));
    }
    if let Some(uuid) = response.uuid.as_deref() {
        lines.push(format!("uuid: {uuid}"));
    }
    if let Some(usage) = usage_summary(response.usage.as_ref()) {
        lines.push(format!("usage: {usage}"));
    }
    lines.push("response:".to_owned());
    lines.push(response.result.clone());
    lines.join("\n")
}

fn usage_summary(usage: Option<&Value>) -> Option<String> {
    let Value::Object(usage) = usage? else {
        return None;
    };
    let summary = usage
        .iter()
        .filter_map(|(key, value)| match value {
            Value::Number(number) => Some((key.clone(), number.to_string())),
            Value::String(text) if !text.is_empty() => Some((key.clone(), text.clone())),
            _ => None,
        })
        .collect::<BTreeMap<_, _>>();
    (!summary.is_empty()).then(|| {
        summary
            .into_iter()
            .map(|(key, value)| format!("{key}={value}"))
            .collect::<Vec<_>>()
            .join(" ")
    })
}

fn render_duration_ms(duration_ms: u64) -> String {
    if duration_ms < 1_000 {
        return format!("{duration_ms}ms");
    }
    let seconds = duration_ms as f64 / 1_000.0;
    format!("{seconds:.3}s")
}

fn generation_from_wire(raw: u64) -> Generation {
    let mut generation = Generation::genesis();
    for _ in 1..raw {
        generation = generation.next();
    }
    generation
}