use std::{path::PathBuf, process::Command};

fn main() {
    // set what version string to use for the build
    // currently it depends on what git outputs, or if failed use "unknown"
    {
        // paths are relative to the workspace root
        println!("cargo:rerun-if-changed=server/build.rs");
        println!("cargo:rerun-if-changed=.git/HEAD");

        let cargo_toml_version = {
            let version = env!("CARGO_PKG_VERSION");

            if version.is_empty() {
                None
            } else {
                // format is the literal return of what is set in the "Cargo.toml", so to be consistent with git, we modify it to look the same as git (adding "v")
                // also add a inidicator for cargo version
                Some(format!("v{version}[c]"))
            }
        };

        let cargo_toml_or_default = cargo_toml_version.unwrap_or(String::from("unknown"));

        let version = git_version()
            // fallback to Cargo.toml version, if git is unavailable (like having downloaded the source archive)
            .unwrap_or(cargo_toml_or_default);

        println!("cargo:rustc-env=TERMUSIC_VERSION={version}");
    }
}

fn git_version() -> Option<String> {
    let toplevel_dir = Command::new("git")
        .args(["rev-parse", "--show-toplevel"])
        .output()
        .ok()
        .and_then(|v| {
            print_stderr(&v.stderr);

            String::from_utf8(v.stdout).ok()
        })
        .map(|mut v| {
            // remove the ending "\n" that may exist
            v.truncate(v.trim_end().len());

            v
        })
        .map(PathBuf::from)?;

    // not in the termusic repository, but still in a git repo, for example in a AUR build
    // is there maybe a better way to check this?
    if !toplevel_dir.join("Cargo.toml").exists()
        && !toplevel_dir.join("lib").exists()
        && !toplevel_dir.join("tui").exists()
        && !toplevel_dir.join("server").exists()
    {
        return None;
    }

    // How to read the git version, first all the variants:
    // Termusic-server v0.7.11-302-g63396ee5-dirty[g]
    // Termusic-server v0.7.11-302-g63396ee5[g]
    // Termusic-server v0.7.11[g]
    // Termusic-server v0.7.11[c]
    // Termusic-server unknown
    //
    // "Termusic-server" is the binary name
    // "v0.7.11" is the latest tag on the branch
    // "302" is the number of commits since the tag, not always present
    // "g63396ee5" is 2 parts, the "g" in the beginning means "git"
    // the rest "63396ee5" is the abbreviated commit sha
    // "dirty" indicates the build has uncommited changes
    // "[g]" at the end means the version has been gotten from "git" ("[c]" means from "cargo")
    Command::new("git")
        .args(["describe", "--tags", "--always", "--dirty"])
        .output()
        .ok()
        .and_then(|v| {
            print_stderr(&v.stderr);

            String::from_utf8(v.stdout).ok()
        })
        // ignore output if the string gotten is empty
        .and_then(|v| if v.is_empty() { None } else { Some(v) })
        // add a indicator for git version
        .map(|v| format!("{}[g]", v.trim()))
}

/// print stderr for debugging purposes, it will not be shown unless the build.rs panics
fn print_stderr(stderr: &[u8]) {
    if !stderr.is_empty() {
        eprintln!("{}", String::from_utf8_lossy(stderr));
    }
}