//! Shared presentation helpers.

use anyhow::Result;
use oxy_core::hash::ChangeHash;
use oxy_core::objects::Change;
use oxy_core::repo::{Repo, SignatureStatus};
use oxy_core::state::ChangeMeta;

pub fn short_id(c: &Change) -> String {
    c.change_id.short(8)
}

pub fn short_meta_id(c: &ChangeMeta) -> String {
    c.change_id.short(8)
}

/// `n head` / `n heads`.
pub fn plural(n: usize, word: &str) -> String {
    format!("{n} {word}{}", if n == 1 { "" } else { "s" })
}

/// Milliseconds since the Unix epoch as `YYYY-MM-DD HH:MM:SSZ`.
pub fn when(ms: u64) -> String {
    let secs = (ms / 1000) as i64;
    let days = secs.div_euclid(86_400);
    let rem = secs.rem_euclid(86_400);
    // Civil-from-days (Howard Hinnant), UTC.
    let z = days + 719_468;
    let era = z.div_euclid(146_097);
    let doe = z - era * 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;
    let m = if mp < 10 { mp + 3 } else { mp - 9 };
    let y = if m <= 2 { y + 1 } else { y };
    format!("{y:04}-{m:02}-{d:02} {:02}:{:02}:{:02}Z", rem / 3600, (rem % 3600) / 60, rem % 60)
}

/// One line describing how a change is authenticated.
pub fn signature_line(repo: &Repo, h: &ChangeHash) -> Result<String> {
    Ok(match repo.authenticate_change(h)? {
        SignatureStatus::Unsigned => "unsigned".to_string(),
        SignatureStatus::Valid { key, name, email, sealed } => {
            format!("{} by {name} <{email}> key {}", if sealed { "sealed" } else { "signed" }, key.short(12))
        }
        SignatureStatus::Invalid(why) => format!("INVALID signature: {why}"),
    })
}

pub fn deps_line(c: &Change) -> String {
    deps_of(&c.deps)
}

pub fn deps_of(deps: &[oxy_core::hash::ChangeHash]) -> String {
    deps.iter().map(|d| format!("#{}", d.short(12))).collect::<Vec<_>>().join(" ")
}

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

    #[test]
    fn dates() {
        assert_eq!(when(0), "1970-01-01 00:00:00Z");
        assert_eq!(when(1_700_000_000_000), "2023-11-14 22:13:20Z");
        assert_eq!(plural(1, "head"), "1 head");
        assert_eq!(plural(2, "head"), "2 heads");
    }
}