(* Compile with:
   ocamlopt.opt unix.cmxa bordeaux.ml -o bordeaux
 *)

type map_t = {
  map_width: int;
  map_height: int;
  map_data: int array array;
}

let map_create ~width ~height =
  Printf.printf "Creating map..."; flush stdout;
  let rows = Array.init height (fun i -> Array.make width 0) in
    print_newline ();
    { map_width = width;
      map_height = height;
      map_data = rows;
    }

let map_merge_hgt ~map ~filename ~x ~y ~width ~height =
  Printf.printf "Merging %s..." filename; flush stdout;
  try
    let hgt = Unix.open_process_in(Printf.sprintf "unzip -p %s.zip %s" filename filename) in
    let r2 = ref y in
    for r=0 to height-1 do
      let c2 = ref x in
      for c=0 to width-1 do
	let v = (input_byte hgt) lor (input_byte hgt) lsl 8 in
	let v = if (v land 0x8000) <> 0 then -1 - (v lxor 0xffff) else v in
	map.map_data.(!r2).(!c2) <- v;
	incr c2
      done;
      incr r2
    done;
    ignore (Unix.close_process_in hgt);
    print_newline ()
  with _ ->
    Printf.eprintf "Couldn't open %s\n" filename

let map_save ~map ~filename ?(base = 0) ?(x = 0) ?(y = 0) 
             ?(width = map.map_width) ?(height = map.map_height) () =
  Printf.printf "Saving map to %s..." filename; flush stdout;
  try
    let tga = open_out_bin filename in
    let tgaheader = Array.make 18 0 in
    tgaheader.(2) <- 2;
    tgaheader.(12) <- width mod 256;
    tgaheader.(13) <- width / 256;
    tgaheader.(14) <- height mod 256;
    tgaheader.(15) <- height / 256;
    tgaheader.(16) <- 24;
    tgaheader.(17) <- 32;
    for i=0 to 17 do
      output_byte tga tgaheader.(i)
    done;
    for r=y to y+height-1 do
      for c=x to x+width-1 do
	let data = map.map_data.(r).(c) in
	let v = if data < -32000 then 0 else data-base in
	if v < 0 then
	  Printf.eprintf "base too high for %s, should be less than %d\n" filename data;
	output_byte tga 0;
	output_byte tga (v mod 256);
	output_byte tga (v / 256);
      done
    done;
    close_out tga;
    print_newline ()
  with _ ->
    Printf.eprintf "Error while writing %s\n" filename

let _ =
  let map = map_create ~width:2401 ~height:2401 in
  map_merge_hgt ~map:map ~filename:"N44W002.hgt" ~x:0 ~y:1200 ~width:1201 ~height:1201;
  map_merge_hgt ~map:map ~filename:"N45W002.hgt" ~x:0 ~y:0 ~width:1201 ~height:1201;
  map_merge_hgt ~map:map ~filename:"N44W001.hgt" ~x:1200 ~y:1200 ~width:1201 ~height:1201;
  map_merge_hgt ~map:map ~filename:"N45W001.hgt" ~x:1200 ~y:0 ~width:1201 ~height:1201;
  map_save ~map:map ~filename:"bordeaux-ml.tga" ~base:(-70) ()