#load "extLib.cma"

open Printf

type change = { fn: string; ov: string; nv: string; }

class change_log = object (self)
	val changes = DynArray.create ()
	method add_change fn ov nv = DynArray.add changes {fn=fn;ov=ov;nv=nv;}
	method add_maybe  fn ov nv = if ov != nv then self#add_change fn ov nv
	method changes = changes
	method for_update =
		let do_f_eq_v x = x.fn ^ "='" ^ x.nv ^ "'" in
		let do_pair acc x =
			if String.length acc > 0 then acc ^ "," ^ (do_f_eq_v x)
			else (do_f_eq_v x)
		in
		DynArray.fold_left do_pair "" changes
end ;;

class base_model = object (self)
	val changes = new change_log

	method before_insert = ()
	method before_update = ()
	method after_insert  = ()
	method after_update  = ()
end ;;

(* Dynamically generated base user class. Program reads the database structure
	 and generates the model classes *)
class base_user = object (self)
	inherit base_model

	val mutable id = 0
	val mutable code = ""
	val mutable password = ""
	val mutable first_name = ""
	val mutable last_name = ""
	val mutable version = 0

	method save =
		match id with
		| 0 ->
			self#before_insert ;
			sprintf "INSERT INTO users \
		  	(code,password,first_name,last_name,version) VALUES \
		    ('%s','%s','%s','%s',%i)" code password first_name last_name
		    version
		| n ->
			self#before_update ;
			"UPDATE users SET " ^ changes#for_update ^ " WHERE id=" ^
			  (string_of_int id)

	method id = id
	method set_id x =
		changes#add_maybe "id" (string_of_int id) (string_of_int x) ;
		id <- x

	method code = code
	method set_code x =
		changes#add_maybe "code" code x ;
		code <- x

	method password = password
	method set_password x =
		changes#add_maybe "password" password x ;
		password <- x

	method first_name = first_name
	method set_first_name x =
		changes#add_maybe "first_name" first_name x ;
		first_name <- x

	method last_name = last_name
	method set_last_name x =
		changes#add_maybe "last_name" last_name x ;
		last_name <- x

	method version = version
	method set_version x =
		changes#add_maybe "version" (string_of_int version) (string_of_int x) ;
		version <- x
end ;;

class user = object (self)
	inherit base_user

	method before_insert = version <- 1
	method before_update = version <- version + 1
	method full_name = first_name ^ " " ^ last_name
	method blinded_name = sprintf "%s %c." first_name last_name.[0]
end ;;

let u = new user ;;
printf "%s\n" u#save ;;
u#set_id 10 ;;
u#set_code "john" ;;
u#set_first_name "John" ;;
u#set_last_name "Doe" ;;
printf "%s\n" u#save ;;
printf "%s\n" u#blinded_name ;;