readme docs

README.md

@@ -1,3 +1,134 @@
 # Fluence Compute Engine
 
 FCE is intended to run various Wasm binaries. At now, it is in the heavily developing phase.
+
+# Installation
+- Clone this project
+- `cargo install --path <path-to-project/tools/cli>`
+
+# Usage
+- `fce build` in Rust project
+
+# HOW TO: Create App with FCE Modules
+
+## Recommendations:
+
+- Modules architecture should be upwards from `effectors` (WASI modules) that will work with local binaries, local storage and syscalls to `pure modules` that perform business logic.
+- Splitting app to small FCE modules are easier to support, reuse and distribute
+- Each module for its own task (npm like)
+
+## Module project structure
+
+- Init simple rust project `cargo init --bin`
+
+- `Config.toml`:
+```
+[lib]
+name = "wasm_application"
+path = "src/lib.rs"
+crate-type = ["cdylib"]
+
+[dependencies]
+// logger - if you'll use logging
+fluence = { git = "https://github.com/fluencelabs/rust-sdk", features = ["logger"] }
+```
+
+- Methods that will be used outside this module marked with `#[fce]`
+```
+use fluence::fce;
+
+#[fce]
+pub fn get(url: String) -> String {
+...
+}
+```
+- Multiple arguments with primitive Rust types and only one return argument could be used
+
+- Build project with `fce build`
+
+- Copy wasm file from `target/wasm32-wasi/debug` to directory with other modules
+
+- To import other wasm modules to your project use similar code:
+```
+#[fce]
+#[link(wasm_import_module = "wasm_curl.wasm")]
+extern "C" {
+    #[link_name = "get"]
+    pub fn curl_get(url: String) -> String;
+}
+
+#[fce]
+#[link(wasm_import_module = "wasm_local_storage.wasm")]
+extern "C" {
+    #[link_name = "get"]
+    pub fn curl_get(url: String) -> String;
+}
+``` 
+
+## Combine modules to Application
+
+- Create simple Rust project
+- Create `Config.toml` to describe existed wasm modules and give accesses to host binaries and local storage if needed:
+```
+core_modules_dir = "wasm/artifacts/modules"
+
+[[core_module]]
+    name = "wasm_local_storage_with_curl.wasm"
+    mem_pages_count = 100    
+
+   [core_module.imports]
+    curl = "/usr/bin/curl"
+
+    [core_module.wasi]
+    envs = []
+    preopened_files = ["./wasm/artifacts"]
+    mapped_dirs = { "tmp" = "./wasm/artifacts" }
+```
+
+`core_modules_dir` - path to directory with all modules. All subsequent paths will be relative to this path
+
+`[[core_module]]` - modules list
+
+`name` - wasm file name in `core_modules_dir`
+
+`mem_pages_count` - a maximum number of Wasm memory pages that loaded module can use. Each Wasm pages is 65536 bytes long
+
+`[core_module.imports]` - list of available imports
+
+`curl = "/usr/bin/curl"` - gives possibility to call binary file `/usr/bin/curl` as method `curl` in Rust code
+
+Import example:
+```
+#[link(wasm_import_module = "host")]
+extern "C" {
+    fn curl(ptr: i32, size: i32) -> i32;
+}
+```
+It is not possible for now to use `String` as arguments. Use tweek for this:
+```
+fn call_curl(cmd: String) -> String {
+    unsafe {
+        // TODO: better error handling
+        match curl(cmd.as_ptr() as _, cmd.len() as _) {
+            0 => String::from_raw_parts(
+                fluence::internal::get_result_ptr() as _,
+                fluence::internal::get_result_size(),
+                fluence::internal::get_result_size(),
+            ),
+            _ => "host ipfs call failed".to_string(),
+        }
+    }
+}
+```
+Call binary with arguments: `call_curl("-vvv ya.ru")`
+
+`[core_module.wasi]` - this block manages communication with the "outside" world
+`env` - environment variables. Usage: `std::env::var("IPFS_ADDR")`
+`preopened_files` - list of available directories for loaded modules
+`mapped_dirs` - mapping between paths
+
+Working with files as usual:
+```
+fs::write(PathBuf::from("/tmp/somefile"), vec!(1,2,3));
+fs::read(...);
+```