//! Shared commit formats and short reference decorations for log and show.
use crate::{Result, error};
use gix::bstr::ByteSlice;

pub(crate) fn decorations(commit: &gix::Commit<'_>) -> Result<String> {
    let repo = commit.repo;
    let head = crate::head_info(repo)?;
    let mut labels = Vec::new();
    for reference in repo
        .references()
        .map_err(|e| error("refs", e))?
        .all()
        .map_err(|e| error("refs", e))?
    {
        let mut reference = reference.map_err(|e| error("refs", e))?;
        let name = reference.name().as_bstr().to_str_lossy().into_owned();
        if reference
            .peel_to_id()
            .is_ok_and(|id| id.detach() == commit.id)
        {
            let short = reference.name().shorten().to_string();
            labels.push(if head.branch.as_deref() == Some(name.as_ref()) {
                format!("HEAD -> {short}")
            } else if name.starts_with("refs/tags/") {
                format!("tag: {short}")
            } else {
                short
            });
        }
    }
    if head.branch.is_none()
        && repo
            .rev_parse_single("HEAD")
            .is_ok_and(|id| id.detach() == commit.id)
    {
        labels.push("HEAD".into());
    }
    labels.sort_by(|a, b| {
        b.starts_with("HEAD")
            .cmp(&a.starts_with("HEAD"))
            .then_with(|| b.starts_with("tag: ").cmp(&a.starts_with("tag: ")))
            .then_with(|| b.cmp(a))
    });
    Ok(if labels.is_empty() {
        String::new()
    } else {
        format!(" ({})", labels.join(", "))
    })
}
fn relative(seconds: i64) -> String {
    let now = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap()
        .as_secs() as i64;
    let mut diff = now - seconds;
    if diff < 0 {
        return "in the future".into();
    }
    let (count, unit) = if diff < 90 {
        (diff, "second")
    } else {
        diff = (diff + 30) / 60;
        if diff < 90 {
            (diff, "minute")
        } else {
            diff = (diff + 30) / 60;
            if diff < 36 {
                (diff, "hour")
            } else {
                diff = (diff + 12) / 24;
                if diff < 14 {
                    (diff, "day")
                } else if diff < 70 {
                    ((diff + 3) / 7, "week")
                } else if diff < 365 {
                    ((diff + 15) / 30, "month")
                } else if diff < 1825 {
                    let total_months = (diff * 12 + 183) / 365;
                    let years = total_months / 12;
                    let months = total_months % 12;
                    if months != 0 {
                        return format!(
                            "{years} year{}, {months} month{} ago",
                            if years == 1 { "" } else { "s" },
                            if months == 1 { "" } else { "s" }
                        );
                    }
                    (years, "year")
                } else {
                    ((diff + 183) / 365, "year")
                }
            }
        }
    };
    format!("{count} {unit}{} ago", if count == 1 { "" } else { "s" })
}
pub(crate) fn format(commit: &gix::Commit<'_>, template: &str) -> Result<String> {
    let decoded = commit.decode().map_err(|e| error("format", e))?;
    let message = decoded.message.to_str_lossy();
    let author = commit.author().map_err(|e| error("author", e))?;
    let committer = commit.committer().map_err(|e| error("committer", e))?;
    let at = author.time().map_err(|e| error("date", e))?;
    let ct = committer.time().map_err(|e| error("date", e))?;
    let parents = decoded
        .parents
        .iter()
        .map(ToString::to_string)
        .collect::<Vec<_>>();
    let tree = decoded.tree.to_string();
    let id = commit.id.to_string();
    let fields = [
        ("%H", id.clone()),
        ("%h", id[..7].into()),
        ("%P", parents.join(" ")),
        (
            "%p",
            parents
                .iter()
                .map(|p| &p[..7])
                .collect::<Vec<_>>()
                .join(" "),
        ),
        ("%T", tree.clone()),
        ("%t", tree[..7].into()),
        ("%an", author.name.to_string()),
        ("%ae", author.email.to_string()),
        ("%ad", at.format_or_unix(gix::date::time::format::DEFAULT)),
        ("%ar", relative(at.seconds)),
        ("%cn", committer.name.to_string()),
        ("%ce", committer.email.to_string()),
        ("%cd", ct.format_or_unix(gix::date::time::format::DEFAULT)),
        ("%cr", relative(ct.seconds)),
        ("%s", message.lines().next().unwrap_or("").into()),
        (
            "%b",
            message.split_once("\n\n").map_or("", |(_, b)| b).into(),
        ),
        ("%B", message.to_string()),
        ("%d", decorations(commit)?),
        ("%n", "\n".into()),
        ("%%", "%".into()),
    ];
    let expanded = crate::plumbing::format(template, &message);
    let mut rest = expanded.as_str();
    let mut text = String::new();
    while !rest.is_empty() {
        if let Some((key, value)) = fields.iter().find(|(key, _)| rest.starts_with(key)) {
            text.push_str(value);
            rest = &rest[key.len()..];
        } else {
            let ch = rest.chars().next().unwrap();
            text.push(ch);
            rest = &rest[ch.len_utf8()..];
        }
    }
    Ok(text)
}