init

.github/workflows/test.yml

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+name: test
+
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: erlef/setup-beam@v1
+        with:
+          otp-version: "26.0.2"
+          gleam-version: "1.2.1"
+          rebar3-version: "3"
+          # elixir-version: "1.15.4"
+      - run: gleam deps download
+      - run: gleam test
+      - run: gleam format --check src test

.gitignore

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+*.beam
+*.ez
+/build
+erl_crash.dump

README.md

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+# lite_fs
+
+[![Package Version](https://img.shields.io/hexpm/v/lite_fs)](https://hex.pm/packages/lite_fs)
+[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/lite_fs/)
+
+```sh
+gleam add lite_fs
+```
+```gleam
+import lite_fs
+import gleam/io
+
+pub fn main() {
+  // localhost:20202/events
+  // print events to console when you get them
+  lite_fs.start(port: 20202, with: io.debug)
+}
+```
+
+Further documentation can be found at <https://hexdocs.pm/lite_fs>.
+
+## Development
+
+```sh
+gleam run   # Run the project
+gleam test  # Run the tests
+gleam shell # Run an Erlang shell
+```

gleam.toml

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+name = "lite_fs"
+version = "1.0.0"
+
+# Fill out these fields if you intend to generate HTML documentation or publish
+# your project to the Hex package manager.
+#
+description = "litefs event stream client for gleam."
+licences = ["Apache-2.0"]
+repository = { type = "github", user = "VioletBuse", repo = "gleam_litefs" }
+# links = [{ title = "Website", href = "https://gleam.run" }]
+#
+# For a full reference of all the available options, you can have a look at
+# https://gleam.run/writing-gleam/gleam-toml/.
+
+[dependencies]
+gleam_stdlib = ">= 0.34.0 and < 2.0.0"
+httpp = ">= 1.1.0 and < 2.0.0"
+jackson = ">= 1.2.0 and < 2.0.0"
+gleam_http = ">= 3.6.0 and < 4.0.0"
+gleam_erlang = ">= 0.25.0 and < 1.0.0"
+
+[dev-dependencies]
+gleeunit = ">= 1.0.0 and < 2.0.0"

manifest.toml

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+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "certifi", version = "2.12.0", build_tools = ["rebar3"], requirements = [], otp_app = "certifi", source = "hex", outer_checksum = "EE68D85DF22E554040CDB4BE100F33873AC6051387BAF6A8F6CE82272340FF1C" },
+  { name = "gleam_erlang", version = "0.25.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "054D571A7092D2A9727B3E5D183B7507DAB0DA41556EC9133606F09C15497373" },
+  { name = "gleam_http", version = "3.6.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_http", source = "hex", outer_checksum = "8C07DF9DF8CC7F054C650839A51C30A7D3C26482AC241C899C1CEA86B22DBE51" },
+  { name = "gleam_otp", version = "0.10.0", build_tools = ["gleam"], requirements = ["gleam_erlang", "gleam_stdlib"], otp_app = "gleam_otp", source = "hex", outer_checksum = "0B04FE915ACECE539B317F9652CAADBBC0F000184D586AAAF2D94C100945D72B" },
+  { name = "gleam_stdlib", version = "0.38.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "663CF11861179AF415A625307447775C09404E752FF99A24E2057C835319F1BE" },
+  { name = "gleeunit", version = "1.1.2", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "72CDC3D3F719478F26C4E2C5FED3E657AC81EC14A47D2D2DEBB8693CA3220C3B" },
+  { name = "hackney", version = "1.20.1", build_tools = ["rebar3"], requirements = ["certifi", "idna", "metrics", "mimerl", "parse_trans", "ssl_verify_fun", "unicode_util_compat"], otp_app = "hackney", source = "hex", outer_checksum = "FE9094E5F1A2A2C0A7D10918FEE36BFEC0EC2A979994CFF8CFE8058CD9AF38E3" },
+  { name = "httpp", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_erlang", "gleam_http", "gleam_otp", "gleam_stdlib", "hackney"], otp_app = "httpp", source = "hex", outer_checksum = "66E6744054539734B5C769C50873198E36DDFA9A20F9BACD9590888C042FC020" },
+  { name = "idna", version = "6.1.1", build_tools = ["rebar3"], requirements = ["unicode_util_compat"], otp_app = "idna", source = "hex", outer_checksum = "92376EB7894412ED19AC475E4A86F7B413C1B9FBB5BD16DCCD57934157944CEA" },
+  { name = "jackson", version = "1.2.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "jackson", source = "hex", outer_checksum = "4D7F81FE3C46F83D201E8985564E3D986526FEFA5783CDC206A3BFAF1D89B27D" },
+  { name = "metrics", version = "1.0.1", build_tools = ["rebar3"], requirements = [], otp_app = "metrics", source = "hex", outer_checksum = "69B09ADDDC4F74A40716AE54D140F93BEB0FB8978D8636EADED0C31B6F099F16" },
+  { name = "mimerl", version = "1.3.0", build_tools = ["rebar3"], requirements = [], otp_app = "mimerl", source = "hex", outer_checksum = "A1E15A50D1887217DE95F0B9B0793E32853F7C258A5CD227650889B38839FE9D" },
+  { name = "parse_trans", version = "3.4.1", build_tools = ["rebar3"], requirements = [], otp_app = "parse_trans", source = "hex", outer_checksum = "620A406CE75DADA827B82E453C19CF06776BE266F5A67CFF34E1EF2CBB60E49A" },
+  { name = "ssl_verify_fun", version = "1.1.7", build_tools = ["mix", "rebar3", "make"], requirements = [], otp_app = "ssl_verify_fun", source = "hex", outer_checksum = "FE4C190E8F37401D30167C8C405EDA19469F34577987C76DDE613E838BBC67F8" },
+  { name = "unicode_util_compat", version = "0.7.0", build_tools = ["rebar3"], requirements = [], otp_app = "unicode_util_compat", source = "hex", outer_checksum = "25EEE6D67DF61960CF6A794239566599B09E17E668D3700247BC498638152521" },
+]
+
+[requirements]
+gleam_erlang = { version = ">= 0.25.0 and < 1.0.0"}
+gleam_http = { version = ">= 3.6.0 and < 4.0.0" }
+gleam_stdlib = { version = ">= 0.34.0 and < 2.0.0" }
+gleeunit = { version = ">= 1.0.0 and < 2.0.0" }
+httpp = { version = ">= 1.1.0 and < 2.0.0" }
+jackson = { version = ">= 1.2.0 and < 2.0.0" }

src/lite_fs.gleam

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+import gleam/bit_array
+import gleam/bool
+import gleam/bytes_builder.{type BytesBuilder}
+import gleam/dynamic
+import gleam/erlang/process
+import gleam/http.{Get}
+import gleam/http/request.{type Request, Request}
+import gleam/int
+import gleam/option.{None, Some}
+import gleam/result
+import gleam/string
+import httpp/streaming
+import jackson
+
+pub type Message {
+  Shutdown
+}
+
+fn build_request(port: Int) -> Request(BytesBuilder) {
+  Request(
+    method: Get,
+    headers: [#("connection", "keep-alive")],
+    body: bytes_builder.new(),
+    scheme: http.Http,
+    host: "localhost",
+    port: Some(port),
+    path: "/events",
+    query: None,
+  )
+}
+
+fn create_on_data(callback: fn(Event) -> Nil) {
+  fn(msg: streaming.Message, _, _) {
+    case msg {
+      streaming.Done -> Error(process.Normal)
+      streaming.Bits(bits) -> {
+        let evt = {
+          use str <- result.try(bit_array.to_string(bits) |> result.nil_error)
+          use event <- result.try(parse_event(string.trim(str)))
+
+          Ok(event)
+        }
+
+        case evt, bit_array.to_string(bits) {
+          Error(_), Ok(evt_string) ->
+            Error(process.Abnormal("unable to parse event " <> evt_string))
+          Error(_), _ ->
+            Error(process.Abnormal(
+              "received bits from server that could not be parsed into string",
+            ))
+          Ok(event), _ -> {
+            callback(event)
+            Ok(Nil)
+          }
+        }
+      }
+    }
+  }
+}
+
+fn on_message(message: Message, _, _) {
+  case message {
+    Shutdown -> Error(process.Normal)
+  }
+}
+
+fn on_error(_, _, _) {
+  Error(process.Abnormal("error received"))
+}
+
+fn build_request_handler(port: Int, on_event_callback: fn(Event) -> Nil) {
+  let req = build_request(port)
+
+  streaming.StreamingRequestHandler(
+    initial_state: Nil,
+    req: req,
+    on_data: create_on_data(on_event_callback),
+    on_message: on_message,
+    on_error: on_error,
+    initial_response_timeout: 10_000,
+  )
+}
+
+/// start the event listener
+pub fn start(port port: Int, with callback: fn(Event) -> Nil) {
+  build_request_handler(port, callback)
+  |> streaming.start
+}
+
+pub type Primary {
+  Local
+  Remote(hostname: String)
+}
+
+/// The different types of events that you can get from the event stream
+pub type Event {
+  Init(primary_data: Primary)
+  Tx(
+    db: String,
+    tx_id: Int,
+    post_apply_checksum: Int,
+    commit: Int,
+    page_size: Int,
+    timestamp: String,
+  )
+  PrimaryChange(primary_data: Primary)
+}
+
+fn parse_event(json: String) -> Result(Event, Nil) {
+  use parsed_json <- result.try(jackson.parse(json) |> result.nil_error)
+  use resolved_type <- result.try(jackson.resolve_pointer(parsed_json, "/type"))
+  use event_type <- result.try(
+    jackson.decode(resolved_type, dynamic.string) |> result.nil_error,
+  )
+
+  case event_type {
+    "init" -> parse_primary(json, Init)
+    "primaryChange" -> parse_primary(json, PrimaryChange)
+    "tx" -> parse_tx_event(json)
+    _ -> Error(Nil)
+  }
+}
+
+fn parse_primary(
+  event: String,
+  constructor: fn(Primary) -> Event,
+) -> Result(Event, Nil) {
+  use parsed_json <- result.try(jackson.parse(event) |> result.nil_error)
+  use resolved_is_primary <- result.try(jackson.resolve_pointer(
+    parsed_json,
+    "/data/is_primary",
+  ))
+  use is_primary <- result.try(
+    jackson.decode(resolved_is_primary, dynamic.bool) |> result.nil_error,
+  )
+
+  use <- bool.guard(when: is_primary, return: Ok(constructor(Local)))
+
+  use resolved_hostname <- result.try(jackson.resolve_pointer(
+    parsed_json,
+    "/data/hostname",
+  ))
+  use hostname <- result.try(
+    jackson.decode(resolved_hostname, dynamic.string) |> result.nil_error,
+  )
+
+  Ok(constructor(Remote(hostname)))
+}
+
+type TxData {
+  TxData(
+    txid: String,
+    checksum: String,
+    page_size: Int,
+    commit: Int,
+    timestamp: String,
+  )
+}
+
+fn parse_tx_event(event: String) -> Result(Event, Nil) {
+  use json <- result.try(jackson.parse(event) |> result.nil_error)
+  use db_resolved <- result.try(jackson.resolve_pointer(json, "/db"))
+  use db <- result.try(
+    jackson.decode(db_resolved, dynamic.string) |> result.nil_error,
+  )
+  use data <- result.try(jackson.resolve_pointer(json, "/data"))
+
+  use raw_data <- result.try(
+    jackson.decode(
+      data,
+      dynamic.decode5(
+        TxData,
+        dynamic.field("txId", dynamic.string),
+        dynamic.field("postApplyChecksum", dynamic.string),
+        dynamic.field("pageSize", dynamic.int),
+        dynamic.field("commit", dynamic.int),
+        dynamic.field("timestamp", dynamic.string),
+      ),
+    )
+    |> result.nil_error,
+  )
+
+  use tx_id <- result.try(int.base_parse(raw_data.txid, 16))
+  use checksum <- result.try(int.base_parse(raw_data.checksum, 16))
+
+  Ok(Tx(
+    db,
+    tx_id,
+    checksum,
+    raw_data.page_size,
+    raw_data.commit,
+    raw_data.timestamp,
+  ))
+}

test/lite_fs_test.gleam

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+import gleeunit
+import gleeunit/should
+
+pub fn main() {
+  gleeunit.main()
+}
+
+// gleeunit test functions end in `_test`
+pub fn hello_world_test() {
+  1
+  |> should.equal(1)
+}