/**
 * Type definitions for script completion functions
 * 
 * Scripts can export a `getCompletions` function to provide intelligent
 * shell completion suggestions for their arguments.
 * 
 * @example
 * ```typescript
 * export function getCompletions(ctx: CompletionContext): string[] {
 *   const { current, args } = ctx;
 *   
 *   // Suggest values for --key flag
 *   if (current.startsWith("--key=")) {
 *     return ["--key=~/.ssh/id_rsa", "--key=~/.ssh/id_ed25519"];
 *   }
 *   
 *   // Check what's already provided
 *   const hasForce = args.includes("--force");
 *   
 *   // Return available flags
 *   return ["--force", "--dry-run", "--help"].filter(
 *     flag => flag !== "--force" || !hasForce
 *   );
 * }
 * ```
 */

/**
 * Context provided to the completion function
 */
export interface CompletionContext {
  /**
   * All arguments provided so far (excluding the script name)
   * 
   * @example
   * If user typed: `scripts my-script --flag1 value1 --flag2`
   * Then args would be: ["--flag1", "value1", "--flag2"]
   */
  args: string[];

  /**
   * The current word being completed
   * 
   * @example
   * - User typed `--k` and pressed TAB → current = "--k"
   * - User typed `--key=` and pressed TAB → current = "--key="
   * - User typed `--port=22` and pressed TAB → current = "--port=22"
   */
  current: string;

  /**
   * Position of the current word in the args array (0-indexed)
   * 
   * @example
   * If user typed: `scripts my-script arg1 arg2 <TAB>`
   * Then position would be 2 (0=arg1, 1=arg2, 2=current)
   */
  position: number;
}

/**
 * Completion function that scripts should export
 * 
 * This function is called by the loader daemon when the user requests
 * shell completions. It should return an array of completion suggestions
 * based on the provided context.
 * 
 * Can be synchronous or asynchronous (return Promise<string[]>).
 * 
 * @param ctx - Completion context with current state
 * @returns Array of completion suggestions (can be empty), or Promise resolving to array
 * 
 * @remarks
 * - Return empty array if no completions are available
 * - Suggestions are filtered by the shell, so return all matches
 * - Can include partial matches (e.g., "--key=" to prompt for value)
 * - Keep execution fast (< 50ms recommended) for responsive UX
 * - Use Deno APIs to discover filesystem, environment, etc.
 * - Async functions enable API calls, but keep them fast
 * 
 * @example Simple flag completions
 * ```typescript
 * export function getCompletions(ctx: CompletionContext): string[] {
 *   return ["--verbose", "--quiet", "--help"];
 * }
 * ```
 * 
 * @example Async completions with API call
 * ```typescript
 * export async function getCompletions(ctx: CompletionContext): Promise<string[]> {
 *   const { current } = ctx;
 *   
 *   if (current.startsWith("--branch=")) {
 *     try {
 *       const response = await fetch("https://api.github.com/repos/user/repo/branches");
 *       const branches = await response.json();
 *       return branches.map(b => `--branch=${b.name}`);
 *     } catch {
 *       return ["--branch=main"];
 *     }
 *   }
 *   
 *   return ["--branch=", "--help"];
 * }
 * ```
 * 
 * @example Context-aware completions
 * ```typescript
 * export function getCompletions(ctx: CompletionContext): string[] {
 *   const { current, args } = ctx;
 *   
 *   // Complete values for flags
 *   if (current.startsWith("--output=")) {
 *     return ["--output=json", "--output=yaml", "--output=text"];
 *   }
 *   
 *   // Avoid duplicate flags
 *   const usedFlags = new Set(args.map(a => a.split("=")[0]));
 *   
 *   const allFlags = ["--output=", "--verbose", "--format="];
 *   return allFlags.filter(f => !usedFlags.has(f.replace("=", "")));
 * }
 * ```
 * 
 * @example Dynamic completions with filesystem
 * ```typescript
 * export function getCompletions(ctx: CompletionContext): string[] {
 *   const { current } = ctx;
 *   
 *   if (current.startsWith("--config=")) {
 *     try {
 *       // Find config files in current directory
 *       const files: string[] = [];
 *       for (const entry of Deno.readDirSync(".")) {
 *         if (entry.isFile && entry.name.endsWith(".json")) {
 *           files.push(`--config=${entry.name}`);
 *         }
 *       }
 *       return files;
 *     } catch {
 *       return ["--config=config.json"];
 *     }
 *   }
 *   
 *   return ["--config=", "--help"];
 * }
 * ```
 */
export type CompletionFunction = (ctx: CompletionContext) => string[] | Promise<string[]>;