(* This file is part of the Catala compiler, a specification language for tax
   and social benefits computation rules. Copyright (C) 2020 Inria,
   contributors: Emile Rolley <emile.rolley@tuta.io>.

   Licensed under the Apache License, Version 2.0 (the "License"); you may not
   use this file except in compliance with the License. You may obtain a copy of
   the License at

   http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   License for the specific language governing permissions and limitations under
   the License. *)

open Catala_utils
open Shared_ast
open Lcalc.To_ocaml
module D = Dcalc.Ast

(** Contains all format functions used to format a Lcalc Catala program
    representation to a JSON schema describing the corresponding web form. *)
module To_json = struct
  let to_camel_case (s : string) : string =
    String.split_on_char '_' s
    |> (function
         | hd :: tl -> hd :: List.map String.capitalize_ascii tl | l -> l)
    |> String.concat ""

  let format_struct_field_name_camel_case
      (fmt : Format.formatter)
      (v : StructField.t) : unit =
    let s =
      Format.asprintf "%a" StructField.format_t v
      |> String.to_ascii
      |> String.to_snake_case
      |> avoid_keywords
      |> to_camel_case
    in
    Format.fprintf fmt "%s" s

  let fmt_tlit fmt (tlit : typ_lit) =
    match tlit with
    | TInt | TRat -> Format.fprintf fmt "\"type\": \"number\",@\n\"default\": 0"
    | TMoney ->
      Format.fprintf fmt
        "\"type\": \"number\",@\n\"minimum\": 0,@\n\"default\": 0"
    | TBool -> Format.fprintf fmt "\"type\": \"boolean\",@\n\"default\": false"
    | TDate -> Format.fprintf fmt "\"type\": \"string\",@\n\"format\": \"date\""
    | TDuration -> failwith "TODO: tlit duration"
    | TUnit ->
      (* NOTE(@EmileRolley): we previously used the "null" type for unit, but it
         is not working properly so we simply decided to remove it. *)
      ()

  let rec fmt_type fmt (typ : typ) =
    match Mark.remove typ with
    | TLit tlit -> fmt_tlit fmt tlit
    | TStruct sname ->
      Format.fprintf fmt "\"$ref\": \"#/definitions/%a\"" format_struct_name
        sname
    | TEnum ename ->
      Format.fprintf fmt "\"$ref\": \"#/definitions/%a\"" format_enum_name ename
    | TArray t ->
      Format.fprintf fmt
        "\"type\": \"array\",@\n\
         \"default\": [],@\n\
         @[<hov 2>\"items\": {@\n\
         %a@]@\n\
         }"
        fmt_type t
    | _ -> ()

  let fmt_struct_properties
      (ctx : decl_ctx)
      (fmt : Format.formatter)
      (sname : StructName.t) =
    Format.fprintf fmt "%a"
      (Format.pp_print_list
         ~pp_sep:(fun fmt () -> Format.fprintf fmt ",@\n")
         (fun fmt (field_name, field_type) ->
           Format.fprintf fmt "@[<hov 2>\"%a\": {@\n%a@]@\n}"
             format_struct_field_name_camel_case field_name fmt_type field_type))
      (StructField.Map.bindings (find_struct sname ctx))

  let fmt_definitions
      (ctx : decl_ctx)
      (fmt : Format.formatter)
      ((_scope_name, scope_body) : ScopeName.t * 'e scope_body) =
    let get_name t =
      match Mark.remove t with
      | TStruct sname -> Format.asprintf "%a" format_struct_name sname
      | TEnum ename -> Format.asprintf "%a" format_enum_name ename
      | _ -> failwith "unreachable: only structs and enums are collected."
    in
    let rec collect_required_type_defs_from_scope_input
        (input_struct : StructName.t) : typ list =
      let rec collect (acc : typ list) (t : typ) : typ list =
        match Mark.remove t with
        | TStruct s ->
          (* Scope's input is a struct. *)
          (t :: acc) @ collect_required_type_defs_from_scope_input s
        | TEnum e ->
          List.fold_left collect (t :: acc)
            (List.map snd
               (EnumConstructor.Map.bindings
                  (EnumName.Map.find e ctx.ctx_enums)))
        | TArray t -> collect acc t
        | _ -> acc
      in
      find_struct input_struct ctx
      |> StructField.Map.bindings
      |> List.fold_left (fun acc (_, field_typ) -> collect acc field_typ) []
      |> List.sort_uniq (fun t t' -> String.compare (get_name t) (get_name t'))
    in
    let fmt_enum_properties fmt ename =
      let enum_def = find_enum ename ctx in
      Format.fprintf fmt
        "@[<hov 2>\"kind\": {@\n\
         \"type\": \"string\",@\n\
         @[<hov 2>\"anyOf\": [@\n\
         %a@]@\n\
         ]@]@\n\
         }@\n\
         },@\n\
         @[<hov 2>\"allOf\": [@\n\
         %a@]@\n\
         ]@]@\n\
         }"
        (Format.pp_print_list
           ~pp_sep:(fun fmt () -> Format.fprintf fmt ",@\n")
           (fun fmt (enum_cons, _) ->
             Format.fprintf fmt
               "@[<hov 2>{@\n\"type\": \"string\",@\n\"enum\": [\"%a\"]@]@\n}"
               format_enum_cons_name enum_cons))
        (EnumConstructor.Map.bindings enum_def)
        (Format.pp_print_list
           ~pp_sep:(fun fmt () -> Format.fprintf fmt ",@\n")
           (fun fmt (enum_cons, payload_type) ->
             Format.fprintf fmt
               "@[<hov 2>{@\n\
                @[<hov 2>\"if\": {@\n\
                @[<hov 2>\"properties\": {@\n\
                @[<hov 2>\"kind\": {@\n\
                \"const\": \"%a\"@]@\n\
                }@]@\n\
                }@]@\n\
                },@\n\
                @[<hov 2>\"then\": {@\n\
                @[<hov 2>\"properties\": {@\n\
                @[<hov 2>\"payload\": {@\n\
                %a@]@\n\
                }@]@\n\
                }@]@\n\
                }@]@\n\
                }"
               format_enum_cons_name enum_cons fmt_type payload_type))
        (EnumConstructor.Map.bindings enum_def)
    in

    Format.fprintf fmt "@\n%a"
      (Format.pp_print_list
         ~pp_sep:(fun fmt () -> Format.fprintf fmt ",@\n")
         (fun fmt typ ->
           match Mark.remove typ with
           | TStruct sname ->
             Format.fprintf fmt
               "@[<hov 2>\"%a\": {@\n\
                \"type\": \"object\",@\n\
                @[<hov 2>\"properties\": {@\n\
                %a@]@\n\
                }@]@\n\
                }"
               format_struct_name sname
               (fmt_struct_properties ctx)
               sname
           | TEnum ename ->
             Format.fprintf fmt
               "@[<hov 2>\"%a\": {@\n\
                \"type\": \"object\",@\n\
                @[<hov 2>\"properties\": {@\n\
                %a@]@]@\n"
               format_enum_name ename fmt_enum_properties ename
           | _ -> ()))
      (collect_required_type_defs_from_scope_input
         scope_body.scope_body_input_struct)

  let format_program
      (fmt : Format.formatter)
      (scope : ScopeName.t)
      (prgm : 'm Lcalc.Ast.program) =
    let scope_body = Program.get_scope_body prgm scope in
    Format.fprintf fmt
      "{@[<hov 2>@\n\
       \"type\": \"object\",@\n\
       \"@[<hov 2>definitions\": {%a@]@\n\
       },@\n\
       \"@[<hov 2>properties\": {@\n\
       %a@]@\n\
       }@]@\n\
       }"
      (fmt_definitions prgm.decl_ctx)
      (scope, scope_body)
      (fmt_struct_properties prgm.decl_ctx)
      scope_body.scope_body_input_struct
end

let run
    link_modules
    output
    optimize
    check_invariants
    avoid_exceptions
    closure_conversion
    ex_scope
    options =
  let prg, ctx, _ =
    Driver.Passes.lcalc options ~link_modules ~optimize ~check_invariants
      ~avoid_exceptions ~closure_conversion
  in
  let output_file, with_output =
    Driver.Commands.get_output_format options ~ext:"_schema.json" output
  in
  with_output
  @@ fun fmt ->
  let scope_uid = Driver.Commands.get_scope_uid ctx ex_scope in
  Message.emit_debug
    "Writing JSON schema corresponding to the scope '%a' to the file %s..."
    ScopeName.format_t scope_uid
    (Option.value ~default:"stdout" output_file);
  To_json.format_program fmt scope_uid prg

let term =
  let open Cmdliner.Term in
  const run
  $ Cli.Flags.link_modules
  $ Cli.Flags.output
  $ Cli.Flags.optimize
  $ Cli.Flags.check_invariants
  $ Cli.Flags.avoid_exceptions
  $ Cli.Flags.closure_conversion
  $ Cli.Flags.ex_scope

let () =
  Driver.Plugin.register "json_schema" term
    ~doc:
      "Catala plugin for generating {{:https://json-schema.org} JSON schemas} \
       used to build forms for the Catala website."