(** Demonstration of enhanced header processing functionality
    
    This example shows how to use the new structured header parsing 
    capabilities that implement RFC 8621 Section 4.1.2 access patterns.
*)

open Jmap_email

let demo_header_parsing () =
  Printf.printf "=== JMAP Header Processing Demo ===\n\n";
  
  (* Create some example headers *)
  let from_header = Header.create_unsafe 
    ~name:"From" 
    ~value:"\"John Smith\" <john@example.com>, jane@example.com" () in
  
  let subject_header = Header.create_unsafe
    ~name:"Subject"
    ~value:" =?UTF-8?Q?Test_Subject_with_=C3=A9ncoding?= " () in
    
  let message_id_header = Header.create_unsafe
    ~name:"Message-ID"
    ~value:"<abc123@example.com>" () in
    
  let date_header = Header.create_unsafe
    ~name:"Date" 
    ~value:"2024-01-15T10:30:00Z" () in
    
  let list_post_header = Header.create_unsafe
    ~name:"List-Post"
    ~value:"<mailto:list@example.com>, <http://example.com/post>" () in

  (* Demonstrate Raw access pattern *)
  Printf.printf "1. Raw Access Pattern:\n";
  Printf.printf "   From (raw): %s\n" (Header.as_raw from_header);
  Printf.printf "   Subject (raw): %s\n\n" (Header.as_raw subject_header);

  (* Demonstrate Text access pattern *)
  Printf.printf "2. Text Access Pattern (with RFC 2047 decoding):\n";
  (match Header.as_text subject_header with
   | Ok text -> Printf.printf "   Subject (decoded): %s\n" text
   | Error _ -> Printf.printf "   Subject: Parse error\n");
  Printf.printf "\n";

  (* Demonstrate Addresses access pattern *)
  Printf.printf "3. Addresses Access Pattern:\n";
  (match Header.as_addresses from_header with
   | Ok addresses ->
       Printf.printf "   From addresses (%d found):\n" (List.length addresses);
       List.iteri (fun i addr ->
         match Address.name addr with
         | Some name -> Printf.printf "     %d. %s <%s>\n" (i+1) name (Address.email addr)
         | None -> Printf.printf "     %d. <%s>\n" (i+1) (Address.email addr)
       ) addresses
   | Error _ -> Printf.printf "   From: Parse error\n");
  Printf.printf "\n";

  (* Demonstrate MessageIds access pattern *)
  Printf.printf "4. MessageIds Access Pattern:\n";
  (match Header.as_message_ids message_id_header with
   | Ok ids ->
       Printf.printf "   Message-ID: [%s]\n" (String.concat "; " ids)
   | Error _ -> Printf.printf "   Message-ID: Parse error\n");
  Printf.printf "\n";

  (* Demonstrate Date access pattern *)
  Printf.printf "5. Date Access Pattern:\n";
  (match Header.as_date date_header with
   | Ok date -> 
       Printf.printf "   Date: %f (timestamp)\n" (Jmap.Date.to_timestamp date)
   | Error _ -> Printf.printf "   Date: Parse error\n");
  Printf.printf "\n";

  (* Demonstrate URLs access pattern *)
  Printf.printf "6. URLs Access Pattern:\n";
  (match Header.as_urls list_post_header with
   | Ok urls ->
       Printf.printf "   List-Post URLs: [%s]\n" (String.concat "; " urls)
   | Error _ -> Printf.printf "   List-Post: Parse error\n");
  Printf.printf "\n";

  (* Demonstrate utility functions *)
  Printf.printf "7. Header List Utilities:\n";
  let headers = [from_header; subject_header; message_id_header] in
  (match Header.find_and_parse_as_text headers "Subject" with
   | Some text -> Printf.printf "   Found Subject: %s\n" text
   | None -> Printf.printf "   Subject not found or not parseable\n");
  (match Header.find_and_parse_as_addresses headers "From" with
   | Some addrs -> Printf.printf "   Found %d From addresses\n" (List.length addrs)
   | None -> Printf.printf "   From not found or not parseable\n");
  
  Printf.printf "\n=== Demo Complete ===\n"

let () = demo_header_parsing ()