//! 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");

    }

}