use std::collections::HashMap;
use std::sync::Arc;
use std::time::Duration;

use crate::client_common::tools::ToolSpec;
use crate::codex::Session;
use crate::codex::TurnContext;
use crate::config::Config;
use crate::exec_env::create_env;
use crate::features::Feature;
use crate::function_tool::FunctionCallError;
use crate::tools::ToolRouter;
use crate::tools::code_mode_description::code_mode_tool_reference;
use crate::tools::context::FunctionToolOutput;
use crate::tools::context::SharedTurnDiffTracker;
use crate::tools::context::ToolPayload;
use crate::tools::js_repl::resolve_compatible_node;
use crate::tools::router::ToolCall;
use crate::tools::router::ToolCallSource;
use crate::truncate::TruncationPolicy;
use crate::truncate::formatted_truncate_text_content_items_with_policy;
use crate::truncate::truncate_function_output_items_with_policy;
use crate::unified_exec::resolve_max_tokens;
use codex_protocol::models::FunctionCallOutputContentItem;
use serde::Deserialize;
use serde::Serialize;
use serde_json::Value as JsonValue;
use tokio::io::AsyncBufReadExt;
use tokio::io::AsyncReadExt;
use tokio::io::AsyncWriteExt;
use tokio::io::BufReader;

const CODE_MODE_RUNNER_SOURCE: &str = include_str!("code_mode_runner.cjs");
const CODE_MODE_BRIDGE_SOURCE: &str = include_str!("code_mode_bridge.js");
pub(crate) const PUBLIC_TOOL_NAME: &str = "exec";

#[derive(Clone)]
struct ExecContext {
    session: Arc<Session>,
    turn: Arc<TurnContext>,
    tracker: SharedTurnDiffTracker,
}

#[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq, Serialize)]
#[serde(rename_all = "snake_case")]
enum CodeModeToolKind {
    Function,
    Freeform,
}

#[derive(Clone, Debug, Serialize)]
struct EnabledTool {
    tool_name: String,
    namespace: Vec<String>,
    name: String,
    kind: CodeModeToolKind,
}

#[derive(Serialize)]
#[serde(tag = "type", rename_all = "snake_case")]
enum HostToNodeMessage {
    Init {
        enabled_tools: Vec<EnabledTool>,
        stored_values: HashMap<String, JsonValue>,
        source: String,
    },
    Response {
        id: String,
        code_mode_result: JsonValue,
    },
}

#[derive(Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
enum NodeToHostMessage {
    ToolCall {
        id: String,
        name: String,
        #[serde(default)]
        input: Option<JsonValue>,
    },
    Result {
        content_items: Vec<JsonValue>,
        stored_values: HashMap<String, JsonValue>,
        #[serde(default)]
        error_text: Option<String>,
        #[serde(default)]
        max_output_tokens_per_exec_call: Option<usize>,
    },
}

pub(crate) fn instructions(config: &Config) -> Option<String> {
    if !config.features.enabled(Feature::CodeMode) {
        return None;
    }

    let mut section = String::from("## Exec\n");
    section.push_str(&format!(
        "- Use `{PUBLIC_TOOL_NAME}` for JavaScript execution in a Node-backed `node:vm` context.\n",
    ));
    section.push_str(&format!(
        "- `{PUBLIC_TOOL_NAME}` is a freeform/custom tool. Direct `{PUBLIC_TOOL_NAME}` calls must send raw JavaScript tool input. Do not wrap code in JSON, quotes, or markdown code fences.\n",
    ));
    section.push_str(&format!(
        "- Direct tool calls remain available while `{PUBLIC_TOOL_NAME}` is enabled.\n",
    ));
    section.push_str(&format!(
        "- `{PUBLIC_TOOL_NAME}` uses the same Node runtime resolution as `js_repl`. If needed, point `js_repl_node_path` at the Node binary you want Codex to use.\n",
    ));
    section.push_str("- Import nested tools from `tools.js`, for example `import { exec_command } from \"tools.js\"` or `import { tools } from \"tools.js\"`. Namespaced tools are also available from `tools/<namespace...>.js`; MCP tools use `tools/mcp/<server>.js`, for example `import { append_notebook_logs_chart } from \"tools/mcp/ologs.js\"`. `tools[name]` and identifier wrappers like `await exec_command(args)` remain available for compatibility. Nested tool calls resolve to their code-mode result values.\n");
    section.push_str(&format!(
        "- Import `{{ output_text, output_image, set_max_output_tokens_per_exec_call, store, load }}` from `@openai/code_mode` (or `\"openai/code_mode\"`). `output_text(value)` surfaces text back to the model and stringifies non-string objects with `JSON.stringify(...)` when possible. `output_image(imageUrl)` appends an `input_image` content item for `http(s)` or `data:` URLs. `store(key, value)` persists JSON-serializable values across `{PUBLIC_TOOL_NAME}` calls in the current session, and `load(key)` returns a cloned stored value or `undefined`. `set_max_output_tokens_per_exec_call(value)` sets the token budget used to truncate the final Rust-side result of the current `{PUBLIC_TOOL_NAME}` execution; the default is `10000`. This guards the overall `{PUBLIC_TOOL_NAME}` output, not individual nested tool invocations. The returned content starts with a separate `Script completed` or `Script failed` text item that includes wall time. When truncation happens, the final text may include `Total output lines:` and the usual `…N tokens truncated…` marker.\n",
    ));
    section.push_str(
        "- Function tools require JSON object arguments. Freeform tools require raw strings.\n",
    );
    section.push_str("- `add_content(value)` remains available for compatibility. It is synchronous and accepts a content item, an array of content items, or a string. Structured nested-tool results should be converted to text first, for example with `JSON.stringify(...)`.\n");
    section
        .push_str("- Only content passed to `output_text(...)`, `output_image(...)`, or `add_content(value)` is surfaced back to the model.");
    Some(section)
}

pub(crate) async fn execute(
    session: Arc<Session>,
    turn: Arc<TurnContext>,
    tracker: SharedTurnDiffTracker,
    code: String,
) -> Result<FunctionToolOutput, FunctionCallError> {
    let exec = ExecContext {
        session,
        turn,
        tracker,
    };
    let enabled_tools = build_enabled_tools(&exec).await;
    let stored_values = exec.session.services.code_mode_store.stored_values().await;
    let source = build_source(&code, &enabled_tools).map_err(FunctionCallError::RespondToModel)?;
    execute_node(exec, source, enabled_tools, stored_values)
        .await
        .map_err(FunctionCallError::RespondToModel)
}

async fn execute_node(
    exec: ExecContext,
    source: String,
    enabled_tools: Vec<EnabledTool>,
    stored_values: HashMap<String, JsonValue>,
) -> Result<FunctionToolOutput, String> {
    let node_path = resolve_compatible_node(exec.turn.config.js_repl_node_path.as_deref()).await?;
    let started_at = std::time::Instant::now();

    let env = create_env(&exec.turn.shell_environment_policy, None);
    let mut cmd = tokio::process::Command::new(&node_path);
    cmd.arg("--experimental-vm-modules");
    cmd.arg("--eval");
    cmd.arg(CODE_MODE_RUNNER_SOURCE);
    cmd.current_dir(&exec.turn.cwd);
    cmd.env_clear();
    cmd.envs(env);
    cmd.stdin(std::process::Stdio::piped())
        .stdout(std::process::Stdio::piped())
        .stderr(std::process::Stdio::piped())
        .kill_on_drop(true);

    let mut child = cmd
        .spawn()
        .map_err(|err| format!("failed to start {PUBLIC_TOOL_NAME} Node runtime: {err}"))?;
    let stdout = child
        .stdout
        .take()
        .ok_or_else(|| format!("{PUBLIC_TOOL_NAME} runner missing stdout"))?;
    let stderr = child
        .stderr
        .take()
        .ok_or_else(|| format!("{PUBLIC_TOOL_NAME} runner missing stderr"))?;
    let mut stdin = child
        .stdin
        .take()
        .ok_or_else(|| format!("{PUBLIC_TOOL_NAME} runner missing stdin"))?;

    let stderr_task = tokio::spawn(async move {
        let mut reader = BufReader::new(stderr);
        let mut buf = Vec::new();
        let _ = reader.read_to_end(&mut buf).await;
        String::from_utf8_lossy(&buf).trim().to_string()
    });

    write_message(
        &mut stdin,
        &HostToNodeMessage::Init {
            enabled_tools: enabled_tools.clone(),
            stored_values,
            source,
        },
    )
    .await?;

    let mut stdout_lines = BufReader::new(stdout).lines();
    let mut pending_result = None;
    while let Some(line) = stdout_lines
        .next_line()
        .await
        .map_err(|err| format!("failed to read {PUBLIC_TOOL_NAME} runner stdout: {err}"))?
    {
        if line.trim().is_empty() {
            continue;
        }
        let message: NodeToHostMessage = serde_json::from_str(&line).map_err(|err| {
            format!("invalid {PUBLIC_TOOL_NAME} runner message: {err}; line={line}")
        })?;
        match message {
            NodeToHostMessage::ToolCall { id, name, input } => {
                let response = HostToNodeMessage::Response {
                    id,
                    code_mode_result: call_nested_tool(exec.clone(), name, input).await,
                };
                write_message(&mut stdin, &response).await?;
            }
            NodeToHostMessage::Result {
                content_items,
                stored_values,
                error_text,
                max_output_tokens_per_exec_call,
            } => {
                exec.session
                    .services
                    .code_mode_store
                    .replace_stored_values(stored_values)
                    .await;
                pending_result = Some((
                    output_content_items_from_json_values(content_items)?,
                    error_text,
                    max_output_tokens_per_exec_call,
                ));
                break;
            }
        }
    }

    drop(stdin);

    let status = child
        .wait()
        .await
        .map_err(|err| format!("failed to wait for {PUBLIC_TOOL_NAME} runner: {err}"))?;
    let stderr = stderr_task
        .await
        .map_err(|err| format!("failed to collect {PUBLIC_TOOL_NAME} stderr: {err}"))?;
    let wall_time = started_at.elapsed();
    let success = status.success();

    let Some((mut content_items, error_text, max_output_tokens_per_exec_call)) = pending_result
    else {
        let message = if stderr.is_empty() {
            format!("{PUBLIC_TOOL_NAME} runner exited without returning a result (status {status})")
        } else {
            stderr
        };
        return Err(message);
    };

    if !success {
        let error_text = error_text.unwrap_or_else(|| {
            if stderr.is_empty() {
                format!("Process exited with status {status}")
            } else {
                stderr
            }
        });
        content_items.push(FunctionCallOutputContentItem::InputText {
            text: format!("Script error:\n{error_text}"),
        });
    }

    let mut content_items =
        truncate_code_mode_result(content_items, max_output_tokens_per_exec_call);
    prepend_script_status(&mut content_items, success, wall_time);
    Ok(FunctionToolOutput::from_content(
        content_items,
        Some(success),
    ))
}

async fn write_message(
    stdin: &mut tokio::process::ChildStdin,
    message: &HostToNodeMessage,
) -> Result<(), String> {
    let line = serde_json::to_string(message)
        .map_err(|err| format!("failed to serialize {PUBLIC_TOOL_NAME} message: {err}"))?;
    stdin
        .write_all(line.as_bytes())
        .await
        .map_err(|err| format!("failed to write {PUBLIC_TOOL_NAME} message: {err}"))?;
    stdin
        .write_all(b"\n")
        .await
        .map_err(|err| format!("failed to write {PUBLIC_TOOL_NAME} message newline: {err}"))?;
    stdin
        .flush()
        .await
        .map_err(|err| format!("failed to flush {PUBLIC_TOOL_NAME} message: {err}"))
}

fn prepend_script_status(
    content_items: &mut Vec<FunctionCallOutputContentItem>,
    success: bool,
    wall_time: Duration,
) {
    let wall_time_seconds = ((wall_time.as_secs_f32()) * 10.0).round() / 10.0;
    let header = format!(
        "{}\nWall time {wall_time_seconds:.1} seconds\nOutput:\n",
        if success {
            "Script completed"
        } else {
            "Script failed"
        }
    );
    content_items.insert(0, FunctionCallOutputContentItem::InputText { text: header });
}

fn build_source(user_code: &str, enabled_tools: &[EnabledTool]) -> Result<String, String> {
    let enabled_tools_json = serde_json::to_string(enabled_tools)
        .map_err(|err| format!("failed to serialize enabled tools: {err}"))?;
    Ok(CODE_MODE_BRIDGE_SOURCE
        .replace(
            "__CODE_MODE_ENABLED_TOOLS_PLACEHOLDER__",
            &enabled_tools_json,
        )
        .replace("__CODE_MODE_USER_CODE_PLACEHOLDER__", user_code))
}

fn truncate_code_mode_result(
    items: Vec<FunctionCallOutputContentItem>,
    max_output_tokens_per_exec_call: Option<usize>,
) -> Vec<FunctionCallOutputContentItem> {
    let max_output_tokens = resolve_max_tokens(max_output_tokens_per_exec_call);
    let policy = TruncationPolicy::Tokens(max_output_tokens);
    if items
        .iter()
        .all(|item| matches!(item, FunctionCallOutputContentItem::InputText { .. }))
    {
        let (truncated_items, _) =
            formatted_truncate_text_content_items_with_policy(&items, policy);
        return truncated_items;
    }

    truncate_function_output_items_with_policy(&items, policy)
}

async fn build_enabled_tools(exec: &ExecContext) -> Vec<EnabledTool> {
    let router = build_nested_router(exec).await;
    let mut out = Vec::new();
    for spec in router.specs() {
        let tool_name = spec.name().to_string();
        if tool_name == PUBLIC_TOOL_NAME {
            continue;
        }

        let reference = code_mode_tool_reference(&tool_name);

        out.push(EnabledTool {
            tool_name,
            namespace: reference.namespace,
            name: reference.tool_key,
            kind: tool_kind_for_spec(&spec),
        });
    }
    out.sort_by(|left, right| left.tool_name.cmp(&right.tool_name));
    out.dedup_by(|left, right| left.tool_name == right.tool_name);
    out
}

async fn build_nested_router(exec: &ExecContext) -> ToolRouter {
    let nested_tools_config = exec.turn.tools_config.for_code_mode_nested_tools();
    let mcp_tools = exec
        .session
        .services
        .mcp_connection_manager
        .read()
        .await
        .list_all_tools()
        .await
        .into_iter()
        .map(|(name, tool_info)| (name, tool_info.tool))
        .collect();

    ToolRouter::from_config(
        &nested_tools_config,
        Some(mcp_tools),
        None,
        exec.turn.dynamic_tools.as_slice(),
    )
}

async fn call_nested_tool(
    exec: ExecContext,
    tool_name: String,
    input: Option<JsonValue>,
) -> JsonValue {
    if tool_name == PUBLIC_TOOL_NAME {
        return JsonValue::String(format!("{PUBLIC_TOOL_NAME} cannot invoke itself"));
    }

    let router = build_nested_router(&exec).await;

    let specs = router.specs();
    let payload = if let Some((server, tool)) = exec.session.parse_mcp_tool_name(&tool_name).await {
        match serialize_function_tool_arguments(&tool_name, input) {
            Ok(raw_arguments) => ToolPayload::Mcp {
                server,
                tool,
                raw_arguments,
            },
            Err(error) => return JsonValue::String(error),
        }
    } else {
        match build_nested_tool_payload(&specs, &tool_name, input) {
            Ok(payload) => payload,
            Err(error) => return JsonValue::String(error),
        }
    };

    let call = ToolCall {
        tool_name: tool_name.clone(),
        call_id: format!("{PUBLIC_TOOL_NAME}-{}", uuid::Uuid::new_v4()),
        payload,
    };
    let result = router
        .dispatch_tool_call_with_code_mode_result(
            Arc::clone(&exec.session),
            Arc::clone(&exec.turn),
            Arc::clone(&exec.tracker),
            call,
            ToolCallSource::CodeMode,
        )
        .await;

    match result {
        Ok(result) => result.code_mode_result(),
        Err(error) => JsonValue::String(error.to_string()),
    }
}

fn tool_kind_for_spec(spec: &ToolSpec) -> CodeModeToolKind {
    if matches!(spec, ToolSpec::Freeform(_)) {
        CodeModeToolKind::Freeform
    } else {
        CodeModeToolKind::Function
    }
}

fn tool_kind_for_name(specs: &[ToolSpec], tool_name: &str) -> Result<CodeModeToolKind, String> {
    specs
        .iter()
        .find(|spec| spec.name() == tool_name)
        .map(tool_kind_for_spec)
        .ok_or_else(|| format!("tool `{tool_name}` is not enabled in {PUBLIC_TOOL_NAME}"))
}

fn build_nested_tool_payload(
    specs: &[ToolSpec],
    tool_name: &str,
    input: Option<JsonValue>,
) -> Result<ToolPayload, String> {
    let actual_kind = tool_kind_for_name(specs, tool_name)?;
    match actual_kind {
        CodeModeToolKind::Function => build_function_tool_payload(tool_name, input),
        CodeModeToolKind::Freeform => build_freeform_tool_payload(tool_name, input),
    }
}

fn build_function_tool_payload(
    tool_name: &str,
    input: Option<JsonValue>,
) -> Result<ToolPayload, String> {
    let arguments = serialize_function_tool_arguments(tool_name, input)?;
    Ok(ToolPayload::Function { arguments })
}

fn serialize_function_tool_arguments(
    tool_name: &str,
    input: Option<JsonValue>,
) -> Result<String, String> {
    match input {
        None => Ok("{}".to_string()),
        Some(JsonValue::Object(map)) => serde_json::to_string(&JsonValue::Object(map))
            .map_err(|err| format!("failed to serialize tool `{tool_name}` arguments: {err}")),
        Some(_) => Err(format!(
            "tool `{tool_name}` expects a JSON object for arguments"
        )),
    }
}

fn build_freeform_tool_payload(
    tool_name: &str,
    input: Option<JsonValue>,
) -> Result<ToolPayload, String> {
    match input {
        Some(JsonValue::String(input)) => Ok(ToolPayload::Custom { input }),
        _ => Err(format!("tool `{tool_name}` expects a string input")),
    }
}

fn output_content_items_from_json_values(
    content_items: Vec<JsonValue>,
) -> Result<Vec<FunctionCallOutputContentItem>, String> {
    content_items
        .into_iter()
        .enumerate()
        .map(|(index, item)| {
            serde_json::from_value(item).map_err(|err| {
                format!("invalid {PUBLIC_TOOL_NAME} content item at index {index}: {err}")
            })
        })
        .collect()
}