// tools/read.rs — Read file contents

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

use super::ToolDef;

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

fn default_offset() -> usize { 1 }

pub fn tool() -> super::Tool {
    super::Tool { def: definition(), handler: |_a, v| Box::pin(async move { read_file(&v) }) }
}

fn definition() -> ToolDef {
    ToolDef::new(
        "read_file",
        "Read the contents of a file. Returns the file contents with line numbers.",
        json!({
            "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). Optional."
                },
                "limit": {
                    "type": "integer",
                    "description": "Maximum number of lines to read. Optional."
                }
            },
            "required": ["file_path"]
        }),
    )
}

fn read_file(args: &serde_json::Value) -> Result<String> {
    let args: Args = serde_json::from_value(args.clone())
        .context("invalid read_file arguments")?;

    let content = std::fs::read_to_string(&args.file_path)
        .with_context(|| format!("Failed to read {}", args.file_path))?;

    let lines: Vec<&str> = content.lines().collect();
    let offset = args.offset.max(1) - 1;
    let limit = args.limit.unwrap_or(lines.len());

    let mut output = String::new();
    for (i, line) in lines.iter().skip(offset).take(limit).enumerate() {
        output.push_str(&format!("{:>6}\t{}\n", offset + i + 1, line));
    }

    if output.is_empty() {
        output = "(empty file)\n".to_string();
    }

    Ok(output)
}