open Relational_engine

let default_port = 7777
let default_limit = 50

(* TODO: AbstractValue carries no type tag of its own; we recover the OCaml
   runtime tag here via Obj introspection. This is fragile — it breaks the
   moment a domain stores a boxed integer or a custom block. The right fix is
   a typed value representation in Conventions. *)

(* TODO: Generator.Error is silently treated as end-of-stream here, hiding
   real failures from the client. *)
let materialize_generator gen limit =
  let rec go gen pos acc count =
    if count >= limit then (List.rev acc, true)
    else
      match gen (Some pos) with
      | Generator.Done       -> (List.rev acc, false)
      | Generator.Error _    -> (List.rev acc, false)
      | Generator.Value (t, next) ->
        let mat = match t with
          | Tuple.Materialized m -> Some m
          | Tuple.NonMaterialized _ -> None
        in
        (match mat with
         | None   -> go next (pos + 1) acc count
         | Some m -> go next (pos + 1) (m :: acc) (count + 1))
  in
  go gen 0 [] 0

let materialize_relation storage (rel : Relation.t) limit =
  let gen = Algebra.Memory.to_generator storage rel in
  materialize_generator gen limit

let short_hash (h : string) = String.sub h 0 (min 8 (String.length h))

module BranchOps = Management.Branch.Make(Management.Physical.Memory)
module Dispatch  = Dbms_language.Memory

let get_branch storage =
  match BranchOps.get_head storage with
  | Ok (Some name) -> name
  | _ -> "--"

let tuple_to_sexp (t : Tuple.materialized) =
  let open Sexplib.Sexp in
  List (Tuple.AttributeMap.bindings t.Tuple.attributes
        |> List.map (fun (k, attr) ->
               List [Atom k; Conventions.AbstractValue.sexp_of_t attr.Attribute.value]))

let relation_to_sexp storage db_name db_hash (rel : Relation.t) limit =
  let open Sexplib.Sexp in
  let schema_sexp =
    List (List.map (fun (a, d) -> List [Atom a; Atom d]) rel.Relation.schema)
  in
  let (tuples, truncated) = materialize_relation storage rel limit in
  let rows_sexp = List (List.map tuple_to_sexp tuples) in
  to_string @@ List [
    Atom "relation";
    List [Atom "name";      Atom rel.Relation.name];
    List [Atom "schema";    schema_sexp];
    List [Atom "rows";      rows_sexp];
    List [Atom "row_count"; Atom (string_of_int (List.length tuples))];
    List [Atom "truncated"; Atom (string_of_bool truncated)];
    List [Atom "db_hash";   Atom (short_hash db_hash)];
    List [Atom "db_name";   Atom db_name];
    List [Atom "branch";    Atom (get_branch storage)];
  ]

let ok_response storage db_name db_hash msg =
  let open Sexplib.Sexp in
  to_string @@ List [
    Atom "ok";
    List [Atom "message"; Atom msg];
    List [Atom "db_hash"; Atom (short_hash db_hash)];
    List [Atom "db_name"; Atom db_name];
    List [Atom "branch";  Atom (get_branch storage)];
  ]

let error_response storage db_name db_hash err_sexp =
  let open Sexplib.Sexp in
  to_string @@ List [
    Atom "error";
    err_sexp;
    List [Atom "db_hash"; Atom (short_hash db_hash)];
    List [Atom "db_name"; Atom db_name];
    List [Atom "branch";  Atom (get_branch storage)];
  ]

let advance_head_branch storage new_hash =
  match BranchOps.get_head storage with
  | Ok (Some branch_name) ->
    ignore (BranchOps.update_tip storage ~name:branch_name ~tip:new_hash)
  | _ -> ()

let dbms_dispatch = Dispatch.create [
  (module Drl.Sublanguage.Memory : Dispatch.SubS);
  (module Ddl.Sublanguage.Memory : Dispatch.SubS);
  (module Dml.Sublanguage.Memory : Dispatch.SubS);
  (module Icl.Sublanguage.Memory : Dispatch.SubS);
  (module Dcl.Sublanguage.Memory : Dispatch.SubS);
  (module Scl.Sublanguage.Memory : Dispatch.SubS);
]

let cursor_to_sexp storage db_name db_hash cursor_id rows has_more =
  let open Sexplib.Sexp in
  let row_sexps = List.map tuple_to_sexp rows in
  let rows_sexp = List row_sexps in
  to_string @@ List [
    Atom "cursor";
    List [Atom "id";        Atom cursor_id];
    List [Atom "rows";      rows_sexp];
    List [Atom "row_count"; Atom (string_of_int (List.length row_sexps))];
    List [Atom "has_more";  Atom (string_of_bool has_more)];
    List [Atom "db_hash";   Atom (short_hash db_hash)];
    List [Atom "db_name";   Atom db_name];
    List [Atom "branch";    Atom (get_branch storage)];
  ]

let execute_command storage db_ref cmd =
  let db   = !db_ref in
  let h    = db.Management.Database.hash in
  let name = db.Management.Database.name in
  let ok   = ok_response    storage name in
  let err  = error_response storage name in
  match Dispatch.execute dbms_dispatch storage db cmd with
  | Ok (Sublanguage.Query rel) ->
    relation_to_sexp storage name h rel default_limit
  | Ok (Sublanguage.Transition (new_db, msg)) ->
    db_ref := new_db;
    advance_head_branch storage new_db.Management.Database.hash;
    ok new_db.Management.Database.hash msg
  | Ok (Sublanguage.Cursor { cursor_id; rows; has_more }) ->
    cursor_to_sexp storage name h cursor_id rows has_more
  | Error e ->
    err h (Dispatch.sexp_of_dispatch_error e)

(* TODO: registration failures are silently ignored; a broken prelude
   relation leaves the catalog in a partially-seeded state with no
   indication to the user. *)
let register_prelude_relations storage db =
  let open Prelude.Standard in
  List.fold_left
    (fun db (rel : Relation.t) ->
      match Manipulation.Memory.create_immutable_relation storage db
              ~name:rel.name
              ~schema:rel.schema
              ~generator:(Option.get rel.generator)
              ~membership_criteria:rel.membership_criteria
              ~cardinality:rel.cardinality
      with
      | Ok (new_db, _) -> new_db
      | Error e        ->
        Printf.eprintf "Warning: failed to register prelude relation %s: %s\n%!"
          rel.name (Manipulation.string_of_error e);
        db)
    db
    [ less_than_natural
    ; less_than_or_equal_natural
    ; greater_than_natural
    ; greater_than_or_equal_natural
    ; equal_natural
    ; not_equal_natural
    ; plus_natural
    ; times_natural
    ; minus_natural
    ; divide_natural
    ]

let print_with_time str =
  let now = Unix.gettimeofday () in
  let tm = Unix.localtime now in
  let orange = "\027[38;5;208m" in
  let reset = "\027[0m" in
  let formatted_time =
    Printf.sprintf "%04d-%02d-%02d %02d:%02d:%02d"
      (tm.Unix.tm_year + 1900) (tm.Unix.tm_mon + 1) tm.Unix.tm_mday
      tm.Unix.tm_hour tm.Unix.tm_min tm.Unix.tm_sec
  in
  print_endline @@ Printf.sprintf "%s[%s]%s %s" orange formatted_time reset str

(* TODO: single-threaded accept loop — one slow or hung client blocks all
   others. Should use threads or non-blocking I/O. *)
let handle_client storage db_ref fd =
  let ic = Unix.in_channel_of_descr fd in
  let oc = Unix.out_channel_of_descr fd in
  (try
     while true do
       let line = input_line ic in
       let line = String.trim line in
       if line <> "" then begin
         let response =
           try execute_command storage db_ref line
           with e ->
             let db = !db_ref in
             error_response storage db.Management.Database.name
               db.Management.Database.hash
               Sexplib.Sexp.(List [Atom "uncaught-error"; Atom (Printexc.to_string e)])
         in
         print_with_time response;
         output_string oc (response ^ "\n");
         flush oc
       end
     done
   with End_of_file | Unix.Unix_error _ -> ())

let setup () =
  let ( let* ) = Result.bind in
  let* storage =
    Management.Physical.Memory.create ()
    |> Result.map_error (Fun.const "Failed to create storage")
  in
  let* db =
    Manipulation.Memory.create_database storage ~name:"sakura"
    |> Result.map_error (Fun.const "Failed to create initial database")
  in
  Ok (storage, db)

let register_branch_relations storage db =
  (* Register ephemeral sakura:branch and sakura:head relations backed by
     the raw branch registry — no stored tuples, no circularity. *)
  let register db rel =
    match Manipulation.Memory.create_immutable_relation storage db
            ~name:rel.Relation.name
            ~schema:rel.Relation.schema
            ~generator:(Option.get rel.Relation.generator)
            ~membership_criteria:rel.Relation.membership_criteria
            ~cardinality:rel.Relation.cardinality
    with
    | Ok (db, _) -> db
    | Error e ->
      Printf.eprintf "Warning: failed to register %s: %s\n%!"
        rel.Relation.name (Manipulation.string_of_error e);
      db
  in
  db
  |> Fun.flip register (BranchOps.branch_relation storage)
  |> Fun.flip register (BranchOps.head_relation storage)

let warn_on_error fmt = function
  | Ok ()   -> ()
  | Error e -> Printf.eprintf fmt e

let cursor_gc_max_age  = 300.0  (* 5 minutes *)
let cursor_gc_interval = 60.0   (* run GC at most once per minute *)

let () =
  match setup () with
  | Error msg -> failwith msg
  | Ok (storage, db) ->
    let db = db
      |> register_prelude_relations storage
      |> register_branch_relations storage
    in
    (* Initialise cursor session registry for SCL *)
    let session_reg = Session.create () in
    Scl.Executor.set_sessions session_reg;
    (* Create default master branch in raw registry and set HEAD *)
    BranchOps.create storage ~name:"master" ~tip:db.Management.Database.hash
    |> warn_on_error "Warning: failed to create master branch: %s\n%!";
    BranchOps.checkout storage "master"
    |> warn_on_error "Warning: failed to checkout master: %s\n%!";
    let db_ref = ref db in
    let last_gc = ref 0.0 in
    let sock = Unix.socket Unix.PF_INET Unix.SOCK_STREAM 0 in
    Unix.setsockopt sock Unix.SO_REUSEADDR true;
    Unix.setsockopt sock Unix.SO_REUSEPORT true;
    Unix.bind sock (Unix.ADDR_INET (Unix.inet_addr_loopback, default_port));
    Unix.listen sock 5;
    Printf.printf "Sakura server listening on 127.0.0.1:%d\n" default_port;
    Printf.printf "Database hash: %s\n%!" (short_hash db.Management.Database.hash);
    while true do
      let (client_fd, _addr) = Unix.accept sock in
      handle_client storage db_ref client_fd;
      (try Unix.close client_fd with _ -> ());
      let now = Unix.gettimeofday () in
      if now -. !last_gc >= cursor_gc_interval then begin
        Session.gc session_reg ~max_age:cursor_gc_max_age;
        last_gc := now
      end
    done