use std::{env, process::Command};

fn main() {
    for variable in [
        "LATCHD_VERSION",
        "LATCHD_COMMIT",
        "LATCHD_BUILD_TIME",
        "SOURCE_DATE_EPOCH",
    ] {
        println!("cargo:rerun-if-env-changed={variable}");
    }

    let version = env::var("LATCHD_VERSION")
        .ok()
        .filter(|value| !value.is_empty())
        .unwrap_or_else(|| env!("CARGO_PKG_VERSION").to_owned());
    let commit = env::var("LATCHD_COMMIT")
        .ok()
        .filter(|value| !value.is_empty())
        .or_else(|| git_value(["rev-parse", "--short=12", "HEAD"]))
        .unwrap_or_else(|| "unknown".to_owned());
    let build_time = env::var("LATCHD_BUILD_TIME")
        .ok()
        .filter(|value| !value.is_empty())
        .or_else(|| env::var("SOURCE_DATE_EPOCH").ok())
        .unwrap_or_else(|| "unknown".to_owned());

    println!("cargo:rustc-env=LATCHD_VERSION={version}");
    println!("cargo:rustc-env=LATCHD_COMMIT={commit}");
    println!("cargo:rustc-env=LATCHD_BUILD_TIME={build_time}");
}

fn git_value<const N: usize>(arguments: [&str; N]) -> Option<String> {
    let output = Command::new("git").args(arguments).output().ok()?;
    if !output.status.success() {
        return None;
    }
    let value = String::from_utf8(output.stdout).ok()?;
    let value = value.trim();
    (!value.is_empty()).then(|| value.to_owned())
}