git-cat-file/lib/obj-item.ts

A pure-JavaScript implementation of `git cat-file -p` for Node.js.

/**
 * https://github.com/kawanet/git-cat-file
 */

import type {GCF} from "../types/git-cat-file.d.ts"
import type {ObjStore} from "./obj-store.ts"

export class ObjItem<IMeta> {
    private meta: {[key in keyof IMeta]: string[]}
    private message: string
    private readonly obj: GCF.IObject
    protected readonly store: ObjStore

    constructor(obj: GCF.IObject, store: ObjStore) {
        this.obj = obj
        this.store = store
    }

    getId(): string {
        return this.obj.oid
    }

    private parseMeta(): void {
        if (this.meta) return

        const {data} = this.obj
        // Object.create(null) keeps an attacker-crafted header key like
        // `__proto__` or `constructor` from colliding with the prototype
        // chain when we read `meta[key]` back.
        const meta = this.meta = Object.create(null) as {[key in keyof IMeta]: string[]}
        const lines = data.toString().split(/\r?\n/)
        let headerMode = true
        let lastKey: keyof IMeta
        let message: string

        for (const line of lines) {
            if (headerMode) {
                // A truly empty line ends the header section. RFC 822-style
                // continuation lines start with a single space and append to
                // the previous header's last value (used by `gpgsig` and
                // `mergetag` in commit objects).
                if (line === "") {
                    headerMode = false
                    continue
                }
                if (line.startsWith(" ") && lastKey) {
                    const arr = meta[lastKey]
                    arr[arr.length - 1] += "\n" + line.slice(1)
                    continue
                }
                const [key, val] = splitBySpace(line) as [keyof IMeta, string]
                if (!key) continue
                if (meta[key]) {
                    meta[key].push(val)
                } else {
                    meta[key] = [val]
                }
                lastKey = key
            } else {
                if (message != null) {
                    message += "\n" + line
                } else {
                    message = line
                }
            }
        }

        this.message = message
    }

    getMeta(key: keyof IMeta): string {
        const array = this.getMetaArray(key)
        if (array) {
            if (array.length > 1) return array.join(" ")
            return array[0]
        }
    }

    protected getMetaArray(key: keyof IMeta): string[] {
        this.parseMeta()
        return this.meta[key]
    }

    getMessage(): string {
        this.parseMeta()
        return this.message
    }
}

function splitBySpace(line: string): string[] {
    const sp = line.indexOf(" ")
    return [line.slice(0, sp), line.slice(sp + 1)]
}