/**
 * Typed-routes codegen. From the scanned page routes, emit `app/routes.gen.ts`
 * with a `Routes` map (path -> param types) and an `href()` builder.
 */

import { getRouteParams, type Route } from "./match.ts";
import { nameRoutes } from "./named.ts";

export function generateRoutesFile(pages: Route[]): string {
  const seen = new Set<string>();
  const entries: string[] = [];
  const namedEntries: string[] = [];
  for (const page of [...pages].sort((a, b) => a.raw.localeCompare(b.raw))) {
    if (seen.has(page.raw)) continue;
    seen.add(page.raw);
    const params = page.paramMeta ?? getRouteParams(page.raw);
    const type = params.length
      ? `{ ${params
          .map((param) => {
            const key = `${JSON.stringify(param.name)}${param.optional ? "?" : ""}`;
            const value = param.catchAll ? "string | readonly string[]" : "string";
            return `${key}: ${value}`;
          })
          .join("; ")} }`
      : "Record<string, never>";
    entries.push(`  ${JSON.stringify(page.raw)}: ${type};`);
  }
  for (const page of nameRoutes([...pages].sort((a, b) => a.raw.localeCompare(b.raw))))
    namedEntries.push(`  ${JSON.stringify(page.name)}: ${JSON.stringify(page.raw)};`);

  return `// AUTO-GENERATED by \`wrnexus dev\` - do not edit.
// Typed routes support required, optional, and catch-all parameters.

export interface Routes {
${entries.join("\n") || "  [path: string]: Record<string, string>;"}
}

export interface RouteNames {
${namedEntries.join("\n") || "  [name: string]: string;"}
}

export interface RouteQueries {
  [path: string]: Record<string, string | number | boolean | null | undefined>;
}

export type RoutePath = keyof Routes;
export type RouteName = keyof RouteNames;
export type RouteQuery<P extends RoutePath> = P extends keyof RouteQueries
  ? RouteQueries[P]
  : Record<string, string | number | boolean | null | undefined>;
type RouteValue = string | readonly string[] | undefined;

function encodeRouteValue(value: RouteValue, catchAll: boolean): string {
  if (value === undefined) return "";
  const values = Array.isArray(value) ? value : catchAll ? String(value).split("/") : [String(value)];
  return values.map((part) => encodeURIComponent(part)).join("/");
}

function buildHref(path: string, params: Record<string, RouteValue> = {}): string {
  const output: string[] = [];
  for (const segment of path.split("/").filter(Boolean)) {
    let name: string | undefined;
    let optional = false;
    let catchAll = false;
    if (segment.startsWith("[[") && segment.endsWith("]]")) {
      optional = true;
      name = segment.slice(2, -2);
    } else if (segment.startsWith("[") && segment.endsWith("]")) {
      name = segment.slice(1, -1);
      if (name.endsWith("?")) {
        optional = true;
        name = name.slice(0, -1);
      }
    }
    if (!name) {
      output.push(segment);
      continue;
    }
    if (name.startsWith("...")) {
      catchAll = true;
      name = name.slice(3);
    }
    const value = params[name];
    if (value === undefined && optional) continue;
    if (value === undefined) throw new Error(\`WRN-ROUTE-MISSING-PARAM: Missing route parameter '\${name}'.\`);
    output.push(encodeRouteValue(value, catchAll));
  }
  return "/" + output.filter(Boolean).join("/");
}

export function href<P extends RoutePath>(
  path: P,
  ...args: keyof Routes[P] extends never
    ? []
    : Record<string, never> extends Routes[P]
      ? [params?: Routes[P]]
      : [params: Routes[P]]
): string {
  const params = (args[0] ?? {}) as Record<string, RouteValue>;
  return buildHref(String(path), params);
}

export function route<N extends RouteName>(
  name: N,
  ...args: keyof Routes[RouteNames[N]] extends never
    ? [params?: Routes[RouteNames[N]], query?: RouteQuery<RouteNames[N]>]
    : Record<string, never> extends Routes[RouteNames[N]]
      ? [params?: Routes[RouteNames[N]], query?: RouteQuery<RouteNames[N]>]
      : [params: Routes[RouteNames[N]], query?: RouteQuery<RouteNames[N]>]
): string {
  const paths: Record<RouteName, RoutePath> = ${JSON.stringify(Object.fromEntries(nameRoutes([...pages].sort((a, b) => a.raw.localeCompare(b.raw))).map((page) => [page.name, page.raw])), null, 2)} as Record<RouteName, RoutePath>;
  const output = buildHref(paths[name], (args[0] ?? {}) as Record<string, RouteValue>);
  const query = args[1];
  if (!query) return output;
  const search = new URLSearchParams();
  for (const [key, value] of Object.entries(query))
    if (value !== undefined && value !== null) search.set(key, String(value));
  const text = search.toString();
  return text ? \`\${output}?\${text}\` : output;
}
`;
}
