/**
 * A tuple of name, email, and date for the author or commit
 * info in a commit.
 */
export class CommitIdentity {
    public readonly name: string
    public readonly email: string
    public readonly date: Date
    public readonly tzOffset: number

    /**
     * Parses a Git ident string (GIT_AUTHOR_IDENT or GIT_COMMITTER_IDENT)
     * into a commit identity. Returns null if string could not be parsed.
     */
    public static parseIdentity(identity: string): CommitIdentity | null {
        // See fmt_ident in ident.c:
        //  https://github.com/git/git/blob/3ef7618e6/ident.c#L346
        //
        // Format is "NAME <EMAIL> DATE"
        //  Markus Olsson <j.markus.olsson@gmail.com> 1475670580 +0200
        //
        // Note that `git var` will strip any < and > from the name and email, see:
        //  https://github.com/git/git/blob/3ef7618e6/ident.c#L396
        //
        // Note also that this expects a date formatted with the RAW option in git see:
        //  https://github.com/git/git/blob/35f6318d4/date.c#L191
        //
        const m = identity.match(/^(.*?) <(.*?)> (\d+) (\+|-)?(\d{2})(\d{2})/)
        if (!m) {
            return null
        }

        const name = m[1]
        const email = m[2]
        // The date is specified as seconds from the epoch,
        // Date() expects milliseconds since the epoch.
        const date = new Date(parseInt(m[3], 10) * 1000)

        // The RAW option never uses alphanumeric timezone identifiers and in my
        // testing I've never found it to omit the leading + for a positive offset
        // but the docs for strprintf seems to suggest it might on some systems so
        // we're playing it safe.
        const tzSign = m[4] === '-' ? '-' : '+'
        const tzHH = m[5]
        const tzmm = m[6]

        const tzMinutes = parseInt(tzHH, 10) * 60 + parseInt(tzmm, 10)
        const tzOffset = tzMinutes * (tzSign === '-' ? -1 : 1)

        return new CommitIdentity(name, email, date, tzOffset)
    }

    public constructor(
        name: string,
        email: string,
        date: Date,
        tzOffset?: number
    ) {
        this.name = name
        this.email = email
        this.date = date
        this.tzOffset = tzOffset || new Date().getTimezoneOffset()
    }
}