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import * as path from "path";
export interface MappingEntry {
readonly pattern: string;
readonly paths: ReadonlyArray<string>;
}
export interface Paths {
readonly [key: string]: ReadonlyArray<string>;
}
/**
* Converts an absolute baseUrl and paths to an array of absolute mapping entries.
* The array is sorted by longest prefix.
* Having an array with entries allows us to keep a sorting order rather than
* sort by keys each time we use the mappings.
* @param absoluteBaseUrl
* @param paths
* @param addMatchAll
*/
export function getAbsoluteMappingEntries(
absoluteBaseUrl: string,
paths: Paths,
addMatchAll: boolean
): ReadonlyArray<MappingEntry> {
// Resolve all paths to absolute form once here, and sort them by
// longest prefix once here, this saves time on each request later.
// We need to put them in an array to preserve the sorting order.
const sortedKeys = sortByLongestPrefix(Object.keys(paths));
const absolutePaths: Array<MappingEntry> = [];
for (const key of sortedKeys) {
absolutePaths.push({
pattern: key,
paths: paths[key].map((pathToResolve) =>
path.join(absoluteBaseUrl, pathToResolve)
),
});
}
// If there is no match-all path specified in the paths section of tsconfig, then try to match
// all paths relative to baseUrl, this is how typescript works.
if (!paths["*"] && addMatchAll) {
absolutePaths.push({
pattern: "*",
paths: [`${absoluteBaseUrl.replace(/\/$/, "")}/*`],
});
}
return absolutePaths;
}
/**
* Sort path patterns.
* If a module name can be matched with multiple patterns then pattern with the longest prefix will be picked.
*/
function sortByLongestPrefix(arr: Array<string>): Array<string> {
return arr
.concat()
.sort((a: string, b: string) => getPrefixLength(b) - getPrefixLength(a));
}
function getPrefixLength(pattern: string): number {
const prefixLength = pattern.indexOf("*");
return pattern.substr(0, prefixLength).length;
}