//! Write a TODO item.
//!
//! Appends a new unchecked TODO entry to the session's `TODO.md`
//! file with an optional priority marker and emits a
//! `TurnEvent::TodoUpdate` for the TUI.

use crate::tools::{Tool, ToolCtx};
use anyhow::Result;
use serde_json::{json, Value};
use tracing::{info, instrument};

/// Tool that adds an item to the session TODO list.
///
/// Flow: parse item + optional priority → append `- [priority] item\n`
/// to `TODO.md` → write file → push `TurnEvent::TodoUpdate` if events
/// channel exists → confirm addition.
pub struct Todowrite;

impl Tool for Todowrite {
    fn name(&self) -> &'static str {
        "todowrite"
    }

    fn description(&self) -> &'static str {
        "Add an item to the TODO list"
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "item": {
                    "type": "string",
                    "description": "TODO item text"
                },
                "priority": {
                    "type": "string",
                    "enum": ["high", "medium", "low"],
                    "description": "Priority level"
                }
            },
            "required": ["item"]
        })
    }

    #[instrument(skip(self, ctx, args))]
    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let item = crate::tools::arg_str(args, "item")?;
        let priority = args
            .get("priority")
            .and_then(|v| v.as_str())
            .unwrap_or("medium");

        info!(item, priority, "todowrite invoked");

        let todo_line = format!("- [{}] {}\n", priority, item);
        
        let todo_path = ctx.session_dir.join("TODO.md");
        let mut content = std::fs::read_to_string(&todo_path).unwrap_or_default();
        content.push_str(&todo_line);
        
        let _ = std::fs::write(&todo_path, &content);

        if let Some(events) = &ctx.turn_events {
            if let Ok(mut q) = events.lock() {
                q.push_back(crate::TurnEvent::TodoUpdate(content));
            }
        }

        info!(item, priority, "TODO item added");
        Ok(format!("[{}] TODO added: {}", priority, item))
    }
}