use std::path::PathBuf;
use std::process::Command;
use std::str;

/// This macro creates the version string during compilation from the
/// current environment
#[macro_export]
macro_rules! get_version_info {
    () => {{
        let major = std::env!("CARGO_PKG_VERSION_MAJOR").parse::<u8>().unwrap();
        let minor = std::env!("CARGO_PKG_VERSION_MINOR").parse::<u8>().unwrap();
        let patch = std::env!("CARGO_PKG_VERSION_PATCH").parse::<u16>().unwrap();
        let crate_name = String::from(std::env!("CARGO_PKG_NAME"));

        let host_compiler = std::option_env!("RUSTC_RELEASE_CHANNEL").map(str::to_string);
        let commit_hash = std::option_env!("GIT_HASH").map(str::to_string);
        let commit_date = std::option_env!("COMMIT_DATE").map(str::to_string);

        $crate::VersionInfo {
            major,
            minor,
            patch,
            host_compiler,
            commit_hash,
            commit_date,
            crate_name,
        }
    }};
}

/// This macro can be used in `build.rs` to automatically set the needed
/// environment values, namely `GIT_HASH`, `COMMIT_DATE` and
/// `RUSTC_RELEASE_CHANNEL`
#[macro_export]
macro_rules! setup_version_info {
    () => {{
        let _ = $crate::rerun_if_git_changes();
        println!(
            "cargo:rustc-env=GIT_HASH={}",
            $crate::get_commit_hash().unwrap_or_default()
        );
        println!(
            "cargo:rustc-env=COMMIT_DATE={}",
            $crate::get_commit_date().unwrap_or_default()
        );
        println!("cargo:rustc-env=RUSTC_RELEASE_CHANNEL={}", $crate::get_channel());
    }};
}

// some code taken and adapted from RLS and cargo
pub struct VersionInfo {
    pub major: u8,
    pub minor: u8,
    pub patch: u16,
    pub host_compiler: Option<String>,
    pub commit_hash: Option<String>,
    pub commit_date: Option<String>,
    pub crate_name: String,
}

impl std::fmt::Display for VersionInfo {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let hash = self.commit_hash.clone().unwrap_or_default();
        let hash_trimmed = hash.trim();

        let date = self.commit_date.clone().unwrap_or_default();
        let date_trimmed = date.trim();

        if (hash_trimmed.len() + date_trimmed.len()) > 0 {
            write!(
                f,
                "{} {}.{}.{} ({hash_trimmed} {date_trimmed})",
                self.crate_name, self.major, self.minor, self.patch,
            )?;
        } else {
            write!(f, "{} {}.{}.{}", self.crate_name, self.major, self.minor, self.patch)?;
        }

        Ok(())
    }
}

impl std::fmt::Debug for VersionInfo {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "VersionInfo {{ crate_name: \"{}\", major: {}, minor: {}, patch: {}",
            self.crate_name, self.major, self.minor, self.patch,
        )?;
        if self.commit_hash.is_some() {
            write!(
                f,
                ", commit_hash: \"{}\", commit_date: \"{}\" }}",
                self.commit_hash.clone().unwrap_or_default().trim(),
                self.commit_date.clone().unwrap_or_default().trim()
            )?;
        } else {
            write!(f, " }}")?;
        }

        Ok(())
    }
}

#[must_use]
fn get_output(cmd: &str, args: &[&str]) -> Option<String> {
    let output = Command::new(cmd).args(args).output().ok()?;
    let mut stdout = output.status.success().then_some(output.stdout)?;
    // Remove trailing newlines.
    while stdout.last().copied() == Some(b'\n') {
        stdout.pop();
    }
    String::from_utf8(stdout).ok()
}

#[must_use]
pub fn rerun_if_git_changes() -> Option<()> {
    // Make sure we get rerun when the git commit changes.
    // We want to watch two files: HEAD, which tracks which branch we are on,
    // and the file for that branch that tracks which commit is is on.

    // First, find the `HEAD` file. This should work even with worktrees.
    let git_head_file = PathBuf::from(get_output("git", &["rev-parse", "--git-path", "HEAD"])?);
    if git_head_file.exists() {
        println!("cargo::rerun-if-changed={}", git_head_file.display());
    }

    // Determine the name of the current ref.
    // This will quit if HEAD is detached.
    let git_head_ref = get_output("git", &["symbolic-ref", "-q", "HEAD"])?;
    // Ask git where this ref is stored.
    let git_head_ref_file = PathBuf::from(get_output("git", &["rev-parse", "--git-path", &git_head_ref])?);
    // If this ref is packed, the file does not exist. However, the checked-out branch is never (?)
    // packed, so we should always be able to find this file.
    if git_head_ref_file.exists() {
        println!("cargo::rerun-if-changed={}", git_head_ref_file.display());
    }

    Some(())
}

#[must_use]
pub fn get_commit_hash() -> Option<String> {
    let mut stdout = get_output("git", &["rev-parse", "HEAD"])?;
    stdout.truncate(10);
    Some(stdout)
}

#[must_use]
pub fn get_commit_date() -> Option<String> {
    get_output("git", &["log", "-1", "--date=short", "--pretty=format:%cd"])
}

#[must_use]
pub fn get_channel() -> String {
    if let Ok(channel) = std::env::var("CFG_RELEASE_CHANNEL") {
        return channel;
    }

    // if that failed, try to ask rustc -V, do some parsing and find out
    if let Some(rustc_output) = get_output("rustc", &["-V"]) {
        if rustc_output.contains("beta") {
            return String::from("beta");
        } else if rustc_output.contains("stable") {
            return String::from("stable");
        }
    }

    // default to nightly
    String::from("nightly")
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_struct_local() {
        let vi = get_version_info!();
        assert_eq!(vi.major, 0);
        assert_eq!(vi.minor, 4);
        assert_eq!(vi.patch, 0);
        assert_eq!(vi.crate_name, "rustc_tools_util");
        // hard to make positive tests for these since they will always change
        assert!(vi.commit_hash.is_none());
        assert!(vi.commit_date.is_none());
    }

    #[test]
    fn test_display_local() {
        let vi = get_version_info!();
        assert_eq!(vi.to_string(), "rustc_tools_util 0.4.0");
    }

    #[test]
    fn test_debug_local() {
        let vi = get_version_info!();
        let s = format!("{vi:?}");
        assert_eq!(
            s,
            "VersionInfo { crate_name: \"rustc_tools_util\", major: 0, minor: 4, patch: 0 }"
        );
    }
}