Nim FFI Wrapper for LibChat (#25)

* remove unneeded code

* Update comment style

* Update Nim side to support safer_ffi

* Fix Introduction from impl

* Updates

.gitignore

@@ -24,6 +24,9 @@ target
 
 # Compiled binary
 **/ffi_nim_example
+/nim-bindings/examples/pingpong
+/nim-bindings/libchat
 
 # Temporary data folder
 tmp
+

conversations/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [lib]
-crate-type = ["staticlib"]
+crate-type = ["staticlib","dylib"]
 
 [dependencies]
 blake2.workspace = true

conversations/src/api.rs

@@ -71,8 +71,7 @@ pub fn create_new_private_convo(
     content: c_slice::Ref<'_, u8>,
 ) -> NewConvoResult {
     // Convert input bundle to Introduction
-    let s = String::from_utf8_lossy(&bundle).to_string();
-    let Ok(intro) = Introduction::try_from(s) else {
+    let Ok(intro) = Introduction::try_from(bundle.as_slice()) else {
         return NewConvoResult {
             error_code: ErrorCode::BadIntro as i32,
             convo_id: 0,

conversations/src/inbox/introduction.rs

@@ -31,12 +31,11 @@ impl Into<Vec<u8>> for Introduction {
     }
 }
 
-impl TryFrom<Vec<u8>> for Introduction {
+impl TryFrom<&[u8]> for Introduction {
     type Error = ChatError;
 
-    fn try_from(value: Vec<u8>) -> Result<Self, Self::Error> {
-        let str_value =
-            String::from_utf8(value).map_err(|_| ChatError::BadParsing("Introduction"))?;
+    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+        let str_value = String::from_utf8_lossy(value);
         let parts: Vec<&str> = str_value.splitn(3, ':').collect();
 
         if parts[0] != "Bundle" {

nim-bindings/README.md

@@ -0,0 +1,8 @@
+# Nim-bindings
+
+A Nim wrapping class that exposes LibChat functionality.
+
+
+## Getting Started
+
+`nimble pingpong` - Run the pingpong example.

nim-bindings/conversations_example.nimble

@@ -0,0 +1,21 @@
+# Package
+
+version       = "0.1.0"
+author        = "libchat"
+description   = "Nim Bindings for LibChat"
+license       = "MIT"
+srcDir        = "src"
+bin           = @["libchat"]
+
+
+# Dependencies
+
+requires "nim >= 2.2.4"
+requires "results"
+
+# Build Rust library before compiling Nim
+before build:
+  exec "cargo build --release --manifest-path ../Cargo.toml"
+
+task pingpong, "Run pingpong example":
+  exec "nim c -r --path:src examples/pingpong.nim"

nim-bindings/examples/pingpong.nim

@@ -0,0 +1,22 @@
+import results
+
+import ../src/libchat
+
+proc pingpong() =
+
+  var raya = newConversationsContext()
+  var saro = newConversationsContext()
+
+
+  # Perform out of band Introduction
+  let intro = raya.createIntroductionBundle().expect("[Raya] Couldn't create intro bundle")
+  echo "Raya's Intro Bundle: ",intro
+
+  var (convo_sr, payload) = saro.createNewPrivateConvo(intro,"Hey Raya").expect("[Saro] Couldn't create convo")
+  echo "ConvoHandle::  ", convo_sr
+  echo "Payload::      ", payload
+  
+
+
+when isMainModule:
+  pingpong()

nim-bindings/src/bindings.nim

@@ -0,0 +1,155 @@
+# Nim FFI bindings for libchat conversations library
+
+import std/[os]
+
+# Dynamic library path resolution
+# Can be overridden at compile time with -d:CONVERSATIONS_LIB:"path/to/lib"
+# Or at runtime via LIBCHAT_LIB environment variable
+when defined(macosx):
+  const DEFAULT_LIB_NAME = "liblogos_chat.dylib"
+elif defined(linux):
+  const DEFAULT_LIB_NAME = "liblogos_chat.so"
+elif defined(windows):
+  const DEFAULT_LIB_NAME = "logos_chat.dll"
+else:
+  const DEFAULT_LIB_NAME = "logos_chat"
+
+# Try to find the library relative to the source file location at compile time
+const
+  thisDir = currentSourcePath().parentDir()
+  projectRoot = thisDir.parentDir().parentDir()
+  releaseLibPath = projectRoot / "target" / "release" / DEFAULT_LIB_NAME
+  debugLibPath = projectRoot / "target" / "debug" / DEFAULT_LIB_NAME
+
+# Default to release path, can be overridden with -d:CONVERSATIONS_LIB:"..."
+const CONVERSATIONS_LIB* {.strdefine.} = releaseLibPath
+
+# Error codes (must match Rust ErrorCode enum)
+const
+  ErrNone* = 0'i32
+  ErrBadPtr* = -1'i32
+  ErrBadConvoId* = -2'i32
+  ErrBadIntro* = -3'i32
+  ErrNotImplemented* = -4'i32
+  ErrBufferExceeded* = -5'i32
+  ErrUnknownError* = -6'i32
+
+# Opaque handle type for Context
+type ContextHandle* = pointer
+type ConvoHandle* = uint32
+
+type
+  ## Slice for passing byte arrays to safer_ffi functions
+  SliceUint8* = object
+    `ptr`*: ptr uint8
+    len*: csize_t
+
+  ## Vector type returned by safer_ffi functions (must be freed)
+  VecUint8* = object
+    `ptr`*: ptr uint8
+    len*: csize_t
+    cap*: csize_t
+
+  ## repr_c::String type from safer_ffi
+  ReprCString* = object
+    `ptr`*: ptr char
+    len*: csize_t
+    cap*: csize_t
+
+  ## Payload structure for FFI (matches Rust Payload struct)
+  Payload* = object
+    address*: ReprCString
+    data*: VecUint8
+
+  ## Vector of Payloads returned by safer_ffi functions
+  VecPayload* = object
+    `ptr`*: ptr Payload
+    len*: csize_t
+    cap*: csize_t
+
+  ## Result structure for create_intro_bundle
+  ## error_code is 0 on success, negative on error (see ErrorCode)
+  PayloadResult* = object
+    error_code*: int32
+    payloads*: VecPayload
+
+  ## Result from create_new_private_convo
+  ## error_code is 0 on success, negative on error (see ErrorCode)
+  NewConvoResult* = object
+    error_code*: int32
+    convo_id*: uint32
+    payloads*: VecPayload
+
+# FFI function imports
+
+## Creates a new libchat Context
+## Returns: Opaque handle to the context. Must be freed with destroy_context()
+proc create_context*(): ContextHandle {.importc, dynlib: CONVERSATIONS_LIB.}
+
+## Destroys a context and frees its memory
+## - handle must be a valid pointer from create_context()
+## - handle must not be used after this call
+proc destroy_context*(ctx: ContextHandle) {.importc, dynlib: CONVERSATIONS_LIB.}
+
+## Creates an intro bundle for sharing with other users
+## Returns: Number of bytes written to bundle_out, or negative error code
+proc create_intro_bundle*(
+  ctx: ContextHandle,
+  bundle_out: SliceUint8,
+): int32 {.importc, dynlib: CONVERSATIONS_LIB.}
+
+## Creates a new private conversation
+## Returns: NewConvoResult struct - check error_code field (0 = success, negative = error)
+## The result must be freed with destroy_convo_result()
+proc create_new_private_convo*(
+  ctx: ContextHandle,
+  bundle: SliceUint8,
+  content: SliceUint8,
+): NewConvoResult {.importc, dynlib: CONVERSATIONS_LIB.}
+
+## Free the result from create_new_private_convo
+proc destroy_convo_result*(result: NewConvoResult) {.importc, dynlib: CONVERSATIONS_LIB.}
+
+## Free the PayloadResult
+proc destroy_payload_result*(result: PayloadResult) {.importc, dynlib: CONVERSATIONS_LIB.}
+
+# ============================================================================
+# Helper functions
+# ============================================================================
+
+## Create a SliceRefUint8 from a string
+proc toSlice*(s: string): SliceUint8 =
+  if s.len == 0:
+    SliceUint8(`ptr`: nil, len: 0)
+  else:
+    SliceUint8(`ptr`: cast[ptr uint8](unsafeAddr s[0]), len: csize_t(s.len))
+
+## Create a SliceRefUint8 from a seq[byte]
+proc toSlice*(s: seq[byte]): SliceUint8 =
+  if s.len == 0:
+    SliceUint8(`ptr`: nil, len: 0)
+  else:
+    SliceUint8(`ptr`: cast[ptr uint8](unsafeAddr s[0]), len: csize_t(s.len))
+
+## Convert a ReprCString to a Nim string
+proc `$`*(s: ReprCString): string =
+  if s.ptr == nil or s.len == 0:
+    return ""
+  result = newString(s.len)
+  copyMem(addr result[0], s.ptr, s.len)
+
+## Convert a VecUint8 to a seq[byte]
+proc toSeq*(v: VecUint8): seq[byte] =
+  if v.ptr == nil or v.len == 0:
+    return @[]
+  result = newSeq[byte](v.len)
+  copyMem(addr result[0], v.ptr, v.len)
+
+## Access payloads from VecPayload
+proc `[]`*(v: VecPayload, i: int): Payload =
+  assert i >= 0 and csize_t(i) < v.len
+  cast[ptr UncheckedArray[Payload]](v.ptr)[i]
+
+## Get length of VecPayload
+proc len*(v: VecPayload): int =
+  int(v.len)

nim-bindings/src/libchat.nim

@@ -0,0 +1,88 @@
+import results
+import bindings
+
+type
+  LibChat* = object
+    handle: ContextHandle
+    buffer_size: int
+
+  PayloadResult* = object
+    address*: string
+    data*: seq[uint8]
+
+## Create a new conversations context
+proc newConversationsContext*(): LibChat =
+
+  result.handle = create_context()
+  result.buffer_size = 256
+  if result.handle.isNil:
+    raise newException(IOError, "Failed to create context")
+
+## Destroy the context and free resources
+proc destroy*(ctx: var LibChat) =
+
+  if not ctx.handle.isNil:
+    destroy_context(ctx.handle)
+    ctx.handle = nil
+
+## Helper proc to create buffer of sufficient size
+proc getBuffer*(ctx: LibChat): seq[byte] =
+  newSeq[byte](ctx.buffer_size)
+
+## Generate a Introduction Bundle
+proc createIntroductionBundle*(ctx: LibChat): Result[string, string] =
+  if ctx.handle == nil:
+    return err("Context handle is nil")
+
+  var buffer = ctx.getBuffer()
+  var slice = buffer.toSlice()
+  let len = create_intro_bundle(ctx.handle, slice)
+
+  if len < 0:
+    return err("Failed to create intro bundle: " & $len)
+
+  buffer.setLen(len)
+  return ok(cast[string](buffer))
+
+## Create a Private Convo
+proc createNewPrivateConvo*(ctx: LibChat, bundle: string, content: string): Result[(ConvoHandle, seq[PayloadResult]), string] =
+  if ctx.handle == nil:
+    return err("Context handle is nil")
+
+  if bundle.len == 0:
+    return err("bundle is zero length")
+  if content.len == 0:
+    return err("content is zero length")
+
+  let res = bindings.create_new_private_convo(
+    ctx.handle,
+    bundle.toSlice(),
+    content.toSlice()
+  )
+
+  if res.error_code != 0:
+    result = err("Failed to create private convo: " & $res.error_code)
+    destroy_convo_result(res)
+    return
+
+  # Convert payloads to Nim types
+  var payloads = newSeq[PayloadResult](res.payloads.len)
+  for i in 0 ..< res.payloads.len:
+    let p = res.payloads[int(i)]
+    payloads[int(i)] = PayloadResult(
+      address: $p.address,
+      data: p.data.toSeq()
+    )
+
+  let convoId = res.convo_id
+
+  # Free the result
+  destroy_convo_result(res)
+
+  return ok((convoId, payloads))
+
+
+proc `=destroy`(x: var LibChat) =
+  # Automatically free handle when the destructor is called
+  if x.handle != nil:
+    x.destroy()