Merge pull request 'Functorize with PCLOCK' (#15) from functorize-pclock into main

Reviewed-on: https://git.robur.io/robur/git-kv/pulls/15

.gitignore

@@ -0,0 +1,11 @@
+_build
+setup.data
+setup.log
+doc/*.html
+*.native
+*.byte
+*.so
+*.tar.gz
+_tests
+*.merlin
+*.install

.ocamlformat

@@ -0,0 +1,17 @@
+version=0.23.0
+profile=conventional
+break-struct=natural
+break-infix=fit-or-vertical
+break-sequences=false
+break-collection-expressions=wrap
+break-separators=before
+exp-grouping=preserve
+parens-tuple=multi-line-only
+space-around-lists=false
+space-around-records=false
+space-around-arrays=false
+break-fun-decl=smart
+cases-exp-indent=2
+sequence-style=before
+field-space=tight
+break-before-in=auto

app/dune

@@ -1,4 +1,4 @@
 (executable
  (name mgit)
  (public_name mgit)
- (libraries logs.fmt fmt.tty git-unix git-kv))
+ (libraries mirage-clock-unix logs.fmt fmt.tty git-unix git-kv))

app/mgit.ml

@@ -1,4 +1,5 @@
 let () = Printexc.record_backtrace true
+module Store = Git_kv.Make (Pclock)
 
 let reporter ppf =
   let report src level ~over k msgf =
@@ -25,17 +26,17 @@ open Rresult
 open Lwt.Infix
 
 let get ~quiet store key =
-  Git_kv.get store key >>= function
+  Store.get store key >>= function
   | Ok contents when not quiet ->
     Fmt.pr "@[<hov>%a@]\n%!" (Hxd_string.pp Hxd.default) contents ;
     Lwt.return (Ok 0)
   | Ok _ -> Lwt.return (Ok 0)
   | Error err ->
-    if not quiet then Fmt.epr "%a.\n%!" Git_kv.pp_error err ;
+    if not quiet then Fmt.epr "%a.\n%!" Store.pp_error err ;
     Lwt.return (Ok 1)
 
 let list ~quiet store key =
-  Git_kv.list store key >>= function
+  Store.list store key >>= function
   | Ok lst when not quiet ->
     List.iter (fun (name, k) -> match k with
     | `Dictionary -> Fmt.pr "d %s\n%!" name
@@ -43,7 +44,7 @@ let list ~quiet store key =
     Lwt.return (Ok 0)
   | Ok _ -> Lwt.return (Ok 0)
   | Error err ->
-    if not quiet then Fmt.epr "%a.\n%!" Git_kv.pp_error err ;
+    if not quiet then Fmt.epr "%a.\n%!" Store.pp_error err ;
     Lwt.return (Ok 1)
 
 let pull ~quiet store =

git-kv.opam

@@ -12,6 +12,8 @@ depends: [
   "git"               {>= "3.9.0"}
   "mirage-kv"         {>= "4.0.0"}
   "git-unix"
+  "mirage-clock-unix"
+  "mirage-clock"
   "ptime"
 ]
 

src/dune

@@ -2,4 +2,4 @@
   (name git_kv)
   (public_name git-kv)
   (flags (-w -32))
-  (libraries git ptime mirage-kv))
+  (libraries git ptime mirage-clock mirage-kv))

src/git_kv.ml

@@ -116,21 +116,6 @@ type change = [
   | `Change of key
 ]
 
-type error = Mirage_kv.error
-type write_error = [ `Msg of string
-                   | `Hash_not_found of Digestif.SHA1.t
-                   | `Reference_not_found of Git.Reference.t
-                   | Mirage_kv.write_error ]
-
-let pp_error ppf = Mirage_kv.pp_error ppf
-
-let pp_write_error ppf = function
-  | #Mirage_kv.write_error as err -> Mirage_kv.pp_write_error ppf err
-  | `Reference_not_found _ | `Msg _ as err -> Store.pp_error ppf err
-  | `Hash_not_found hash -> Store.pp_error ppf (`Not_found hash)
-
-let disconnect _t = Lwt.return_unit
-
 module SHA1 = struct
   include Digestif.SHA1
 
@@ -356,6 +341,24 @@ let of_octets ctx ~remote data =
          (Printexc.raw_backtrace_to_string (Printexc.get_raw_backtrace ())) ;
        Lwt.return_error (`Msg "Invalid PACK file"))
 
+module Make (Pclock : Mirage_clock.PCLOCK) = struct
+  type nonrec t = t
+  type key = Mirage_kv.Key.t
+
+  type error = Mirage_kv.error
+  type write_error = [ `Msg of string
+                     | `Hash_not_found of Digestif.SHA1.t
+                     | `Reference_not_found of Git.Reference.t
+                     | Mirage_kv.write_error ]
+  
+  let pp_error ppf = Mirage_kv.pp_error ppf
+  let disconnect _t = Lwt.return_unit
+  
+  let pp_write_error ppf = function
+    | #Mirage_kv.write_error as err -> Mirage_kv.pp_write_error ppf err
+    | `Reference_not_found _ | `Msg _ as err -> Store.pp_error ppf err
+    | `Hash_not_found hash -> Store.pp_error ppf (`Not_found hash)
+
   let exists t key =
     let open Lwt.Infix in
     match t.head with
@@ -483,7 +486,7 @@ let rec unroll_tree t ?head (pred_name, pred_hash) rpath =
   
   let set t key contents =
     let segs = Mirage_kv.Key.segments key in
-  let now () = 0L (* TODO(dinosaure): functorize? *) in
+    let now () = Int64.of_float (Ptime.to_float_s (Ptime.v (Pclock.now_d_ps ()))) in
     match segs with
     | [] -> assert false
     | path ->
@@ -499,6 +502,7 @@ let set t key contents =
       let commit = Store.Value.Commit.make ~tree:tree_root_hash ~author ~committer
         ~parents (Some "Committed by git-kv") in
       Store.write t.store (Git.Value.Commit commit) >>= fun (hash, _) ->
+      Lwt.Infix.(Store.shallow t.store hash >|= Result.ok) >>= fun () ->
       t.head <- Some hash ; Lwt.return_ok ()
   
   let to_write_error (error : Store.error) = match error with
@@ -525,7 +529,7 @@ let batch t ?retries:_ f = f t
   
   let remove t key =
     let segs = Mirage_kv.Key.segments key in
-  let now () = 0L (* TODO(dinosaure): functorize? *) in
+    let now () = Int64.of_float (Ptime.to_float_s (Ptime.v (Pclock.now_d_ps ()))) in
     match List.rev segs, t.head with
     | [], _ -> assert false
     | _, None -> Lwt.return_ok () (* XXX(dinosaure): or [`Not_found]? *)
@@ -542,6 +546,7 @@ let remove t key =
       let commit = Store.Value.Commit.make ~tree:tree_root_hash ~author ~committer
         ~parents:[ head ] (Some "Committed by git-kv") in
       Store.write t.store (Git.Value.Commit commit) >>= fun (hash, _) ->
+      Lwt.Infix.(Store.shallow t.store hash >|= Result.ok) >>= fun () ->
       t.head <- Some hash ; Lwt.return_ok ()
     | name :: pred_name :: rest, Some head ->
       let open Lwt.Infix in
@@ -558,6 +563,7 @@ let remove t key =
           let commit = Store.Value.Commit.make ~tree:tree_root_hash ~author ~committer
             ~parents:[ head ] (Some "Committed by git-kv") in
           Store.write t.store (Git.Value.Commit commit) >>= fun (hash, _) ->
+          Lwt.Infix.(Store.shallow t.store hash >|= Result.ok) >>= fun () ->
           t.head <- Some hash ; Lwt.return_ok ()
         | _ -> Lwt.return_ok ()
   
@@ -571,3 +577,4 @@ let rename t ~source ~dest =
     get t source >>= fun contents ->
     remove t source >>= fun () ->
     set t dest contents
+end

src/git_kv.mli

@@ -1,26 +1,73 @@
-(* The idea is to provide a Mirage_kv.RW interface that is backed by a git
-   repository. The git repository is always (manually) kept in sync with the
-   remote one: either this is the only writer (and thus only set/remove
-   operations need to be pushed, or the API client receives a callback that
-   some update was done, and proceeds with a pull. *)
+(** {1: A Git key-value store.}
 
+    This module implements the ability to manipulate a Git repository as a
+    Key-Value store. It allows you to create a local (in-memory) Git repository
+    that can come from either:
+    - a remote Git repository
+    - a state serialized by the {!val:to_octets} function
+
+    The first case is interesting if you want to be synchronised with the
+    remote repository. The second case can be interesting if we {b don't} want
+    to create a connection at the beginning and desynchronisation between our
+    local and remote repositories {b is not} a problem.
+
+    In the second case, the synchronisation can be done later with {!val:pull}.
+
+    As far as {!val:push} is concerned, a synchronisation with the remote
+    repository is necessary before {b changing} and sending the new information
+    (a use of {!val:Make.set}/{!val:Make.rename} should be preceded by a
+    {!val:pull}). This is because we do not handle conflicts that may exist
+    between your local repository and the remote repository - in other words,
+    if you want to ensure consistency between reading ({!val:pull}) and writing
+    ({!val:push}) to a remote repository, the instance that uses this code
+    should be the only one to handle said remote repository. *)
+
+type t
+(** The type of the Git store. *)
+
+val connect : Mimic.ctx -> string -> t Lwt.t
+(** [connect ctx remote] creates a new Git store which synchronizes
+    with [remote] {i via} protocols available into the given [ctx].
+
+    @raise [Invalid_argument _] if we can not initialize the store, or if
+    we can not fetch the given [remote]. *)
+
+val to_octets : t -> string Lwt.t
+(** [to_octets store] returns a serialized version of the given [store]. *)
+
+val of_octets : Mimic.ctx -> remote:string -> string ->
+  (t, [> `Msg of string]) result Lwt.t
+(** [of_octets ctx ~remote contents] tries to re-create a {!type:t} from its
+    serialized version [contents]. This function does not do I/O and the
+    returned {!type:t} can be out of sync with the given [remote]. We advise
+    to call {!val:pull} to be in-sync with [remote]. *)
+
+type change = [ `Add of Mirage_kv.Key.t
+              | `Remove of Mirage_kv.Key.t
+              | `Change of Mirage_kv.Key.t ]
+
+val pull : t -> (change list, [> `Msg of string ]) result Lwt.t
+(** [pull store] tries to synchronize the remote Git repository with your local
+    [store] Git repository. It returns a list of changes between the old state
+    of your store and what you have remotely. *)
+
+val push : t -> (unit, [> `Msg of string ]) result Lwt.t
+(** [push store] tries to push any changes from your local Git repository
+    [store] to the remoe Git repository. The [push] function can fails for many
+    reasons. Currently, we don't handle merge politics and how we can resolve
+    conflicts between local and remote Git repositories. That mostly means that
+    if you are the only one who push to the Git repository (into a specific
+    branch), everything should be fine. But, if someone else push into the same
+    remote Git repository, your change can be discarded by the remote server
+    (due to conflicts). *)
+
+module Make (Pclock : Mirage_clock.PCLOCK) : sig
   include Mirage_kv.RW
-  with type write_error = [ `Msg of string
+    with type t = t
+     and type write_error = [ `Msg of string
                             | `Hash_not_found of Digestif.SHA1.t
                             | `Reference_not_found of Git.Reference.t
                             | Mirage_kv.write_error ]
   
-val connect : Mimic.ctx -> string -> t Lwt.t
-
-val to_octets : t -> string Lwt.t
-
-val of_octets : Mimic.ctx -> remote:string -> string ->
-  (t, [> `Msg of string]) result Lwt.t
-
-type change = [ `Add of key
-              | `Remove of key
-              | `Change of key ]
-
-val pull : t -> (change list, [> `Msg of string ]) result Lwt.t
-val push : t -> (unit, [> `Msg of string ]) result Lwt.t
   val size : t -> key -> (int, error) result Lwt.t
+end