//! Small helpers that don't depend on git or the web server.

/// Turn "seconds ago" into a short human string like "3 hours ago".
pub fn age(seconds_ago: i64) -> String {
    if seconds_ago < 0 {
        return "in the future".to_string();
    }
    let s = seconds_ago;
    let (n, unit) = if s < 60 {
        return "just now".to_string();
    } else if s < 3600 {
        (s / 60, "minute")
    } else if s < 86_400 {
        (s / 3600, "hour")
    } else if s < 86_400 * 30 {
        (s / 86_400, "day")
    } else if s < 86_400 * 365 {
        (s / (86_400 * 30), "month")
    } else {
        (s / (86_400 * 365), "year")
    };
    let plural = if n == 1 { "" } else { "s" };
    format!("{n} {unit}{plural} ago")
}

/// Seconds since the Unix epoch, right now.
pub fn now_unix() -> i64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0)
}

/// Format a Unix timestamp + UTC offset (in minutes) as "2026-10-31 15:04:05 -0700".
///
/// Implemented by hand (days-to-civil-date algorithm) to avoid pulling in a
/// date/time crate for one function.
pub fn format_time(unix: i64, offset_minutes: i32) -> String {
    let local = unix + offset_minutes as i64 * 60;
    let days = local.div_euclid(86_400);
    let secs = local.rem_euclid(86_400);
    let (y, m, d) = civil_from_days(days);
    let sign = if offset_minutes < 0 { '-' } else { '+' };
    let off = offset_minutes.abs();
    format!(
        "{y:04}-{m:02}-{d:02} {:02}:{:02}:{:02} {sign}{:02}{:02}",
        secs / 3600,
        (secs / 60) % 60,
        secs % 60,
        off / 60,
        off % 60
    )
}

/// Howard Hinnant's algorithm: days since 1970-01-01 -> (year, month, day).
fn civil_from_days(z: i64) -> (i64, u32, u32) {
    let z = z + 719_468;
    let era = z.div_euclid(146_097);
    let doe = z.rem_euclid(146_097);
    let yoe = (doe - doe / 1460 + doe / 36_524 - doe / 146_096) / 365;
    let y = yoe + era * 400;
    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
    let mp = (5 * doy + 2) / 153;
    let d = (doy - (153 * mp + 2) / 5 + 1) as u32;
    let m = if mp < 10 { mp + 3 } else { mp - 9 } as u32;
    (if m <= 2 { y + 1 } else { y }, m, d)
}

/// Check a path that came from a URL, like `src/main.rs`.
///
/// We never touch the filesystem with these paths (files are looked up inside
/// git objects), but we still refuse anything odd so that `..`, absolute paths
/// and control characters can't sneak through. Returns the cleaned path with
/// no leading or trailing slashes ("" means the repo root).
pub fn clean_repo_path(raw: &str) -> Option<String> {
    let mut parts = Vec::new();
    for part in raw.split('/') {
        match part {
            "" => continue, // tolerate "a//b" and leading/trailing slashes
            "." | ".." => return None,
            p if p.chars().any(|c| c.is_control() || c == '\\') => return None,
            p => parts.push(p),
        }
    }
    Some(parts.join("/"))
}

/// Only allow ref names / commit ids made of "normal" characters. This keeps
/// out git revision syntax such as `HEAD@{1}`, `main^`, `:/text` or `a..b`.
pub fn is_safe_ref(name: &str) -> bool {
    !name.is_empty()
        && name.len() <= 200
        && !name.starts_with('-')
        && !name.contains("..")
        && name.chars().all(|c| c.is_ascii_alphanumeric() || matches!(c, '-' | '_' | '.' | '/'))
}

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

    #[test]
    fn ages() {
        assert_eq!(age(5), "just now");
        assert_eq!(age(60), "1 minute ago");
        assert_eq!(age(7200), "2 hours ago");
        assert_eq!(age(86_400 * 3), "3 days ago");
        assert_eq!(age(86_400 * 65), "2 months ago");
        assert_eq!(age(86_400 * 800), "2 years ago");
        assert_eq!(age(-10), "in the future");
    }

    #[test]
    fn formats_time() {
        assert_eq!(format_time(0, 0), "1970-01-01 00:00:00 +0000");
        // 2026-10-31 22:31:00 UTC shown in UTC-7
        assert_eq!(format_time(1_793_485_860, -420), "2026-10-31 15:31:00 -0700");
        assert_eq!(format_time(951_782_400, 330), "2000-02-29 05:30:00 +0530");
    }

    #[test]
    fn repo_paths() {
        assert_eq!(clean_repo_path("src/main.rs").as_deref(), Some("src/main.rs"));
        assert_eq!(clean_repo_path("/src//main.rs/").as_deref(), Some("src/main.rs"));
        assert_eq!(clean_repo_path("").as_deref(), Some(""));
        assert_eq!(clean_repo_path("../etc/passwd"), None);
        assert_eq!(clean_repo_path("src/../../x"), None);
        assert_eq!(clean_repo_path("./x"), None);
        assert_eq!(clean_repo_path("a\\..\\b"), None);
        assert_eq!(clean_repo_path("a\0b"), None);
    }

    #[test]
    fn refs() {
        assert!(is_safe_ref("main"));
        assert!(is_safe_ref("edward/syscalls"));
        assert!(is_safe_ref("v0.15.1"));
        assert!(is_safe_ref("58fc4fd"));
        assert!(!is_safe_ref("HEAD@{1}"));
        assert!(!is_safe_ref("main^"));
        assert!(!is_safe_ref("a..b"));
        assert!(!is_safe_ref("--upload-pack=x"));
        assert!(!is_safe_ref(""));
    }
}

/// Percent-encode a repo path for use inside a URL path (keeps `/`).
/// File names can contain spaces, `#`, `?` and other characters that would
/// otherwise break links.
pub fn encode_path(path: &str) -> String {
    encode(path, true)
}

/// Percent-encode a value for use in a `?key=value` query string.
pub fn encode_query(value: &str) -> String {
    encode(value, false)
}

fn encode(s: &str, keep_slash: bool) -> String {
    let mut out = String::with_capacity(s.len());
    for &b in s.as_bytes() {
        let keep =
            b.is_ascii_alphanumeric() || matches!(b, b'-' | b'_' | b'.' | b'~') || (keep_slash && b == b'/');
        if keep {
            out.push(b as char);
        } else {
            out.push_str(&format!("%{b:02X}"));
        }
    }
    out
}

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

    #[test]
    fn encodes() {
        assert_eq!(encode_path("src/a b#c?.rs"), "src/a%20b%23c%3F.rs");
        assert_eq!(encode_query("edward/syscalls"), "edward%2Fsyscalls");
        assert_eq!(encode_path("ünï"), "%C3%BCn%C3%AF");
    }
}