import assert from 'assert'

import path from 'path'

import patterns from './patterns'

import removeFPTFromPath from '@/versions/lib/remove-fpt-from-path'

/*

This class creates the "permalinks" that power a page's different versions,

where the source for the versions is a content file's frontmatter. The

page.permalinks is an array of objects that looks like this:

[

{

"languageCode": "en",

"pageVersion": "free-pro-team@latest",

"relativePath": "billing/managing-billing-for-your-github-account/index.md",

"title": "Managing billing for your GitHub account",

"hrefWithoutLanguage": "/billing/managing-billing-for-your-github-account",

"href": "/en/billing/managing-billing-for-your-github-account"

},

{

"languageCode": "en",

"pageVersion": "enterprise-cloud@latest",

"relativePath": "billing/managing-billing-for-your-github-account/index.md",

"title": "Managing billing for your GitHub account",

"hrefWithoutLanguage": "/enterprise-cloud@latest/billing/managing-billing-for-your-github-account",

"href": "/en/enterprise-cloud@latest/billing/managing-billing-for-your-github-account"

}

... and so on for each of the content file's supported versions.

]

*/

// String interning pool: deduplicates low-cardinality, highly-repeated values (languageCode, pageVersion)

// across ~975K Permalink instances (~9 languages × ~9 versions × ~65K pages). Because these fields have

// few distinct values (~81 total), the pool stays bounded — do not use intern() for high-cardinality

// fields like relativePath or title, where the pool would grow unbounded and leak memory.

const stringPool = new Map<string, string>()

function intern(s: string): string {

const pooled = stringPool.get(s)

if (pooled !== undefined) return pooled

stringPool.set(s, s)

return s

}

class Permalink {

languageCode: string

pageVersion: string

relativePath: string

title: string

hrefWithoutLanguage: string

href: string

constructor(languageCode: string, pageVersion: string, relativePath: string, title: string) {

this.languageCode = intern(languageCode)

this.pageVersion = intern(pageVersion)

this.relativePath = relativePath

this.title = title

const permalinkSuffix = Permalink.relativePathToSuffix(relativePath)

this.hrefWithoutLanguage = removeFPTFromPath(

path.posix.join('/', pageVersion, permalinkSuffix),

).replace(patterns.trailingSlash, '$1')

this.href = `/${languageCode}${

this.hrefWithoutLanguage === '/' ? '' : this.hrefWithoutLanguage

}`

return this

}

static derive(

languageCode: string,

relativePath: string,

title: string,

applicableVersions: string[],

): Permalink[] {

assert(relativePath, 'relativePath is required')

assert(languageCode, 'languageCode is required')

const permalinks = applicableVersions.map((pageVersion: string) => {

return new Permalink(languageCode, pageVersion, relativePath, title)

})

return permalinks

}

static relativePathToSuffix(relativePath: string): string {

if (relativePath === 'index.md') return '/'

// When you turn `foo/bar.md`, which is a file path, into a URL pathname,

// you just need to chop off the `.md` suffix.

// For `foo/parent/index.md` you can't just chop off the `index.md`

// because it would leave a trailing `/`.

return `/${relativePath.replace(indexmdSuffixRegex, '').replace(mdSuffixRegex, '')}`

}

}

const indexmdSuffixRegex = new RegExp(`${path.sep}index\\.md$`)

const mdSuffixRegex = /\.md$/

export default Permalink