// tools/read.rs — Read file contents

use anyhow::{Context, Result};
use serde::Deserialize;

pub fn tool() -> super::Tool {
    super::Tool {
        name: "read_file",
        description: "Read the contents of a file. Returns the file contents with line numbers.",
        parameters_json: r#"{"type":"object","properties":{"file_path":{"type":"string","description":"Absolute path to the file to read"},"offset":{"type":"integer","description":"Line number to start reading from (1-based)"},"limit":{"type":"integer","description":"Maximum number of lines to read"}},"required":["file_path"]}"#,
        handler: Arc::new(|_a, v| Box::pin(async move { read_file(&v)) }),
    }
}

#[derive(Deserialize)]
struct Args {
    file_path: String,
    #[serde(default = "default_offset")]
    offset: usize,
    limit: Option<usize>,
}
fn default_offset() -> usize { 1 }

fn read_file(args: &serde_json::Value) -> Result<String> {
    let a: Args = serde_json::from_value(args.clone()).context("invalid read_file arguments")?;
    let content = std::fs::read_to_string(&a.file_path)
        .with_context(|| format!("Failed to read {}", a.file_path))?;
    let lines: Vec<&str> = content.lines().collect();
    let start = a.offset.saturating_sub(1);
    let end = a.limit.map_or(lines.len(), |l| (start + l).min(lines.len()));
    if start >= lines.len() {
        return Ok(format!("(file has {} lines, offset {} is past end)", lines.len(), a.offset));
    }
    let mut out = String::new();
    for (i, line) in lines[start..end].iter().enumerate() {
        out.push_str(&format!("{}\t{}\n", start + i + 1, line));
    }
    Ok(out)
}