//! Tool for marking tasks as finished in the session's todo list.

use serde_json::{json, Value};
use anyhow::{Result, anyhow};
use std::path::PathBuf;
use super::super::{Tool, ToolCtx};

/// Tool that marks tasks as finished in the session's todo.md.
pub struct Todofinish;

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

    fn description(&self) -> &'static str {
        "Mark tasks as finished in the session todo list (todo.md). You can mark all tasks as finished by leaving the 'task_index' empty, or specify a 1-based index to finish a specific task."
    }

    fn parameters(&self) -> Value {
        json!({
            "type": "object",
            "properties": {
                "task_index": {
                    "type": "integer",
                    "description": "Optional 1-based index of the task to mark as finished. If omitted, ALL unfinished tasks will be marked as finished."
                }
            }
        })
    }

    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
        let path: PathBuf = ctx.session_dir.join("todo.md");
        if !path.exists() {
            return Ok("No todo.md found in session directory. Nothing to finish.".to_string());
        }

        let content = std::fs::read_to_string(&path)
            .map_err(|e| anyhow!("failed to read todo.md: {}", e))?;

        let task_index = args.get("task_index").and_then(|v| v.as_i64());

        let mut new_content = String::new();
        let mut task_count = 0;
        let mut modified = false;

        for line in content.lines() {
            if line.trim_start().starts_with("- [ ]") {
                task_count += 1;
                if let Some(target) = task_index {
                    if task_count == target {
                        new_content.push_str(&line.replacen("- [ ]", "- [x]", 1));
                        modified = true;
                    } else {
                        new_content.push_str(line);
                    }
                } else {
                    // Mark all as finished
                    new_content.push_str(&line.replacen("- [ ]", "- [x]", 1));
                    modified = true;
                }
            } else {
                new_content.push_str(line);
            }
            new_content.push('\n');
        }

        if !modified {
            return Ok("No unfinished tasks found or index out of bounds.".to_string());
        }

        std::fs::write(&path, new_content)
            .map_err(|e| anyhow!("failed to write to todo.md: {}", e))?;

        if let Some(idx) = task_index {
            Ok(format!("Successfully marked task {} as finished.", idx))
        } else {
            Ok("Successfully marked ALL tasks as finished.".to_string())
        }
    }
}