use std::fs;

use crate::{
    generated::bpf_prog_type::BPF_PROG_TYPE_TRACEPOINT, syscalls::perf_event_open_trace_point,
};

use super::{load_program, perf_attach, Link, ProgramData, ProgramError};

#[derive(Debug)]
pub struct TracePoint {
    pub(crate) data: ProgramData,
}

impl TracePoint {
    pub fn load(&mut self) -> Result<(), ProgramError> {
        load_program(BPF_PROG_TYPE_TRACEPOINT, &mut self.data)
    }

    pub fn attach(&mut self, category: &str, name: &str) -> Result<impl Link, ProgramError> {
        let id = read_sys_fs_trace_point_id(category, name)?;
        let fd = perf_event_open_trace_point(id)
            .map_err(|(_code, io_error)| ProgramError::PerfEventOpenFailed { io_error })?
            as i32;

        perf_attach(&mut self.data, fd)
    }
}

fn read_sys_fs_trace_point_id(category: &str, name: &str) -> Result<u32, ProgramError> {
    let file = format!("/sys/kernel/debug/tracing/events/{}/{}/id", category, name);

    let id = fs::read_to_string(&file).map_err(|e| ProgramError::Other {
        message: format!("error parsing {}: {}", file, e),
    })?;
    let id = id.trim().parse::<u32>().map_err(|e| ProgramError::Other {
        message: format!("error parsing {}: {}", file, e),
    })?;

    Ok(id)
}