SemVer.ts

export type SemVer = {
    major: number;
    minor: number;
    patch: number;
    rc?: number;
    parsedFrom: string;
};

export namespace SemVer {
    const bumpTypes = ["major", "minor", "patch", "rc", "no bump"] as const;

    export type BumpType = typeof bumpTypes[number];

    export function parse(versionStr: string): SemVer {
        const match = versionStr.match(
            /^v?([0-9]+)\.([0-9]+)(?:\.([0-9]+))?(?:-rc.([0-9]+))?$/
        );

        if (!match) {
            throw new Error(`${versionStr} is not a valid semantic version`);
        }

        const semVer: Omit<SemVer, "parsedFrom"> = {
            major: parseInt(match[1]),
            minor: parseInt(match[2]),
            patch: (() => {
                const str = match[3];

                return str === undefined ? 0 : parseInt(str);
            })(),
            ...(() => {
                const str = match[4];
                return str === undefined ? {} : { rc: parseInt(str) };
            })()
        };

        const initialStr = stringify(semVer);

        Object.defineProperty(semVer, "parsedFrom", {
            enumerable: true,
            get: function () {
                const currentStr = stringify(this);

                if (currentStr !== initialStr) {
                    throw new Error(
                        `SemVer.parsedFrom can't be read anymore, the version have been modified from ${initialStr} to ${currentStr}`
                    );
                }

                return versionStr;
            }
        });

        return semVer as any;
    }

    export function stringify(v: Omit<SemVer, "parsedFrom">): string {
        return `${v.major}.${v.minor}.${v.patch}${
            v.rc === undefined ? "" : `-rc.${v.rc}`
        }`;
    }

    /**
     *
     * v1  <  v2  => -1
     * v1 === v2  => 0
     * v1  >  v2  => 1
     *
     */
    export function compare(v1: SemVer, v2: SemVer): -1 | 0 | 1 {
        const sign = (diff: number): -1 | 0 | 1 =>
            diff === 0 ? 0 : diff < 0 ? -1 : 1;
        const noUndefined = (n: number | undefined) => n ?? Infinity;

        for (const level of ["major", "minor", "patch", "rc"] as const) {
            if (noUndefined(v1[level]) !== noUndefined(v2[level])) {
                return sign(noUndefined(v1[level]) - noUndefined(v2[level]));
            }
        }

        return 0;
    }

    /*
    console.log(compare(parse("3.0.0-rc.3"), parse("3.0.0")) === -1 )
    console.log(compare(parse("3.0.0-rc.3"), parse("3.0.0-rc.4")) === -1 )
    console.log(compare(parse("3.0.0-rc.3"), parse("4.0.0")) === -1 )
    */

    export function bumpType(params: {
        versionBehind: string | SemVer;
        versionAhead: string | SemVer;
    }): BumpType | "no bump" {
        const versionAhead =
            typeof params.versionAhead === "string"
                ? parse(params.versionAhead)
                : params.versionAhead;
        const versionBehind =
            typeof params.versionBehind === "string"
                ? parse(params.versionBehind)
                : params.versionBehind;

        if (compare(versionBehind, versionAhead) === 1) {
            throw new Error(
                `Version regression ${stringify(versionBehind)} -> ${stringify(
                    versionAhead
                )}`
            );
        }

        for (const level of ["major", "minor", "patch", "rc"] as const) {
            if (versionBehind[level] !== versionAhead[level]) {
                return level;
            }
        }

        return "no bump";
    }
}