let old_user_version = 2L
let new_user_version = 3L

let set_version version =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    (Printf.sprintf "PRAGMA user_version = %Ld" version)

let new_build_artifact =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    {| CREATE TABLE new_build_artifact (
           id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
           filepath TEXT NOT NULL, -- the path as in the build
           localpath TEXT NOT NULL, -- local path to the file on disk
           sha256 BLOB NOT NULL,
           size INTEGER NOT NULL,
           build INTEGER NOT NULL,

           FOREIGN KEY(build) REFERENCES build(id),
           UNIQUE(build, filepath)
         )
      |}

let new_build_file =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    {| CREATE TABLE new_build_file (
           id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
           filepath TEXT NOT NULL, -- the path as in the build
           localpath TEXT NOT NULL, -- local path to the file on disk
           sha256 BLOB NOT NULL,
           size INTEGER NOT NULL,
           build INTEGER NOT NULL,

           FOREIGN KEY(build) REFERENCES build(id),
           UNIQUE(build, filepath)
         )
      |}

let collect_build_artifact =
  Caqti_request.collect ~oneshot:true
    Caqti_type.unit
    Caqti_type.(tup3 int64 (tup3 string string octets) int64)
    "SELECT id, filepath, localpath, sha256, build FROM build_artifact"

let collect_build_file =
  Caqti_request.collect ~oneshot:true
    Caqti_type.unit
    Caqti_type.(tup3 int64 (tup3 string string octets) int64)
    "SELECT id, filepath, localpath, sha256, build FROM build_file"

let insert_new_build_artifact =
  Caqti_request.exec ~oneshot:true
    Caqti_type.(tup3 int64 (tup4 string string octets int64) int64)
    {| INSERT INTO new_build_artifact (id, filepath, localpath, sha256, size, build)
       VALUES (?, ?, ?, ?, ?, ?)
    |}

let insert_new_build_file =
  Caqti_request.exec ~oneshot:true
    Caqti_type.(tup3 int64 (tup4 string string octets int64) int64)
    {| INSERT INTO new_build_file (id, filepath, localpath, sha256, size, build)
       VALUES (?, ?, ?, ?, ?, ?)
    |}

let drop_build_artifact =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    "DROP TABLE build_artifact"

let drop_build_file =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    "DROP TABLE build_file"

let rename_build_artifact =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    "ALTER TABLE new_build_artifact RENAME TO build_artifact"

let rename_build_file =
  Caqti_request.exec ~oneshot:true
    Caqti_type.unit
    "ALTER TABLE new_build_file RENAME TO build_file"

let migrate (module Db : Caqti_blocking.CONNECTION) =
  let open Rresult.R.Infix in
  Db.find Builder_db.get_application_id () >>= fun application_id ->
  Db.find Builder_db.get_version () >>= fun user_version ->
  if application_id <> Builder_db.application_id || user_version <> old_user_version
  then Error (`Wrong_version (application_id, user_version))
  else
    Db.exec new_build_artifact () >>= fun () ->
    Db.rev_collect_list collect_build_artifact () >>= fun build_artifacts ->
    List.fold_left
      (fun r (id, (filepath, localpath, sha256), build) ->
         r >>= fun () ->
         let stats = Unix.stat localpath in
         Db.exec insert_new_build_artifact
           (id, (filepath, localpath, sha256, Int64.of_int stats.st_size), build))
      (Ok ())
      build_artifacts >>= fun () ->
    Db.exec drop_build_artifact () >>= fun () ->
    Db.exec rename_build_artifact () >>= fun () ->

    Db.exec new_build_file () >>= fun () ->
    Db.rev_collect_list collect_build_file () >>= fun build_files ->
    List.fold_left
      (fun r (id, (filepath, localpath, sha256), build) ->
         r >>= fun () ->
         let stats = Unix.stat localpath in
         Db.exec insert_new_build_file
           (id, (filepath, localpath, sha256, Int64.of_int stats.st_size), build))
      (Ok ())
      build_files >>= fun () ->
    Db.exec drop_build_file () >>= fun () ->
    Db.exec rename_build_file () >>= fun () ->

    Db.exec (set_version new_user_version) ()

(* FIXME: rollback. Requires copying data and creating new table without size column. *)