//! Git version detection. forge requires git 2.38.0 or newer.

use crate::command::{GitCommand, GitEnv};
use crate::error::{Error, Result};

/// Parses `git version` output such as `git version 2.56.0` or `git version 2.39.2.windows.1`.
pub fn parse_git_version(output: &str) -> Option<(u32, u32, u32)> {
    let token = output
        .split_whitespace()
        .find(|t| t.starts_with(|c: char| c.is_ascii_digit()))?;
    let mut parts = token.split('.');
    let major = leading_number(parts.next()?)?;
    let minor = leading_number(parts.next()?)?;
    let patch = parts.next().and_then(leading_number).unwrap_or(0);
    Some((major, minor, patch))
}

/// The number at the start of `s`, so `0-rc1` yields 0.
fn leading_number(s: &str) -> Option<u32> {
    let digits: String = s.chars().take_while(|c| c.is_ascii_digit()).collect();
    digits.parse().ok()
}

fn fmt_version((major, minor, patch): (u32, u32, u32)) -> String {
    format!("{major}.{minor}.{patch}")
}

/// Parses `git version` into (major, minor, patch).
pub async fn git_version(env: &GitEnv) -> Result<(u32, u32, u32)> {
    let out = GitCommand::new(env, "version").output().await?;
    let text = String::from_utf8_lossy(&out);
    parse_git_version(&text).ok_or_else(|| {
        Error::Unavailable(format!("cannot parse git version from {:?}", text.trim()))
    })
}

/// Fails with `Error::TooOld` if git is older than `min`.
pub async fn require_min_version(env: &GitEnv, min: (u32, u32, u32)) -> Result<()> {
    let found = git_version(env).await?;
    if found < min {
        return Err(Error::TooOld {
            found: fmt_version(found),
            required: fmt_version(min),
        });
    }
    Ok(())
}