# srf-lsp

Language Server Protocol implementation for [SRF (Simple Record Format)](https://git.lerch.org/lobo/srf), written in Zig.

Provides real-time parse error diagnostics using the SRF library's parser directly.

## Features

- Parse error diagnostics on open and edit, using the SRF library's parser
  directly: missing or duplicate `#!srfv1`, bad type hints, unparseable values,
  data after `#!eof`, and so on.
- All errors from a parse are reported, not just the first.
- Length-prefix checking for the cases srf does not cover. A numeric type hint
  declares an exact byte count. srf reports a wrong one in compact format, but in
  long format it keeps the declared bytes and discards the rest of the line
  without a word, and a count running past the end of the file fails with no
  location at all. Both are detected here and reported on the offending bytes.
- Hover, covering every construct in the format:
  - `#!srfv1` and each directive, explained.
  - `#!expires`, `#!created` and `#!modified` render their Unix timestamp as a
    UTC date, because nobody can read `1772589213`.
  - Keys and values show the parsed interpretation: numbers, booleans, byte
    counts for strings, and for `binary` values the decoded content when it is
    text (`decoding to 5 bytes: "hello"`) or a note when it is not.
  - Type hints are explained, including a numeric hint's length-prefix meaning.
- Position encoding is negotiated during `initialize` (`utf-8`, `utf-16` or
  `utf-32`), so columns line up even on lines containing multi-byte characters.
- Full-document sync, which matches SRF's single-pass parser.
- stdio transport.

Value interpretation defers to the srf library rather than reimplementing its
rules, so hover and diagnostics cannot disagree about the same text.

Not implemented: completion, document symbols, formatting, goto definition,
semantic tokens, and pull diagnostics (`textDocument/diagnostic`). Requests for
them are answered with `MethodNotFound` rather than left unanswered, and none of
them are advertised as server capabilities.

## Requirements

Zig 0.16.0. Pinned in `.mise.toml`, along with the other tooling.

## Setup

```sh
mise install
```

## Build & Test

```sh
zig build
zig build test
```

The binary is at `zig-out/bin/srf-lsp`.

## Install

The Neovim config below expects `srf-lsp` on `PATH`:

```sh
zig build && install -m755 zig-out/bin/srf-lsp ~/.local/bin/srf-lsp
```

## Neovim Integration

Neovim 0.11 or newer. Add to your config:

```lua
vim.filetype.add({
  extension = {
    srf = "srf",
  },
})

vim.lsp.config("srf_lsp", {
  cmd = { "srf-lsp" },
  filetypes = { "srf" },
  root_markers = { ".git", "/" }, -- single file server
})

vim.lsp.enable("srf_lsp")
```

Check it attached with `:checkhealth vim.lsp` on a `.srf` buffer. Server logs go
to stderr, which Neovim captures in `:LspLog`.

## Combined Setup (with srf-tree-sitter)

For both syntax highlighting and error detection:

```lua
vim.filetype.add({
  extension = {
    srf = "srf",
  },
})

-- Diagnostics
vim.lsp.config("srf_lsp", {
  cmd = { "srf-lsp" },
  filetypes = { "srf" },
  root_markers = { ".git", "/" },
})
vim.lsp.enable("srf_lsp")

-- Syntax highlighting
vim.api.nvim_create_autocmd("User", {
  pattern = "TSUpdate",
  callback = function()
    require("nvim-treesitter.parsers").srf = {
      install_info = {
        url = "https://github.com/elerch/srf-tree-sitter",
        branch = "master",
        queries = "queries",
      },
    }
  end,
})

vim.api.nvim_create_autocmd("FileType", {
  pattern = "srf",
  callback = function(args)
    pcall(vim.treesitter.start, args.buf)
  end,
})
```

Then install the tree-sitter parser (`:TSInstall srf` no-ops if it is already
present, so use `:TSUpdate srf` to pick up a newer grammar):

```vim
:TSUpdate srf
```