open Printf
open ExtLib

let vtk = "140408aX_t01_ch01.vtk";;

type vtkInfo = {
        size: int;
        dimensions: int list;
}

let grabVtkSizeInfo path =
        let ic = open_in path in
        let rec iterateTillInfoFilled tup channel =
                match tup with
                        | (Some x, Some y) -> {size = int_of_string x; dimensions = List.map int_of_string y}
                        | _ ->
                                let line = input_line channel in
                                let nTup = match (line, tup) with
                                        | (_,(size,_)) when (String.exists line "DIMENSIONS") ->
                                                let dim = match (String.nsplit line " ") with
                                                        | _ :: tail -> Some tail
                                                        | _ -> None
                                                in
                                                (size,dim)
                                        | (_,(_,dim)) when (String.exists line "POINT_DATA") ->
                                                let size = match (String.nsplit line " ") with
                                                        | _ :: tail :: [] -> Some tail
                                                        | _ -> None
                                                in
                                                (size, dim)
                                        | _ -> tup
                                in
                                iterateTillInfoFilled nTup channel
                in
        try
                let res = Some (iterateTillInfoFilled (None, None) ic) in
                close_in_noerr ic
                res
        with End_of_file ->
                close_in_noerr ic
                None



let pgm = "test.pgm";;

let oc = open_out pgm;;

let dimInfo =  match (grabVtkSizeInfo vtk) with
        | Some info -> info
        | _ ->
                        eprintf "VTK file contained incomplete dimensional data..."
                        {size = 0; dimensions = []};;

fprintf oc "P2\n%d %d\n%d\n%s" 5 5 255 (String.join " " (List.map string_of_int dimInfo.dimensions));;

let ic = open_in_bin path
seek_in ic ((in_channel_length ic) - dimInfo.size)

let () = match dimInfo.dimensions with
        | x :: y :: _ ->
                        for i = 1 to x do
                                for j = 1 to y do
                                        let b = input_byte in
                                        fprintf oc "%d " b
                                done
                                fprintf oc "\n"
                        done
        | _ -> eprintf "No data to write...";;