1 files changed, 184 insertions, 0 deletions
diff --git a/scripts/luacats_grammar.lua b/scripts/luacats_grammar.lua
new file mode 100644
index 0000000000..ca26c70156
--- /dev/null
+++ b/scripts/luacats_grammar.lua
@@ -0,0 +1,184 @@
+--[[!
+LPEG grammar for LuaCATS
+]]
+
+local lpeg = vim.lpeg
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+local Ct, Cg = lpeg.Ct, lpeg.Cg
+
+--- @param x vim.lpeg.Pattern
+local function rep(x)
+  return x ^ 0
+end
+
+--- @param x vim.lpeg.Pattern
+local function rep1(x)
+  return x ^ 1
+end
+
+--- @param x vim.lpeg.Pattern
+local function opt(x)
+  return x ^ -1
+end
+
+local ws = rep1(S(' \t'))
+local fill = opt(ws)
+
+local any = P(1) -- (consume one character)
+local letter = R('az', 'AZ') + S('_$')
+local num = R('09')
+local ident = letter * rep(letter + num + S '-.')
+local string_single = P "'" * rep(any - P "'") * P "'"
+local string_double = P('"') * rep(any - P('"')) * P('"')
+
+local literal = (string_single + string_double + (opt(P('-')) * num) + P('false') + P('true'))
+
+local lname = (ident + P('...')) * opt(P('?'))
+
+--- @param x string
+local function Pf(x)
+  return fill * P(x) * fill
+end
+
+--- @param x string
+local function Sf(x)
+  return fill * S(x) * fill
+end
+
+--- @param x vim.lpeg.Pattern
+local function paren(x)
+  return Pf('(') * x * fill * P(')')
+end
+
+--- @param x vim.lpeg.Pattern
+local function parenOpt(x)
+  return paren(x) + x
+end
+
+--- @param x vim.lpeg.Pattern
+local function comma1(x)
+  return parenOpt(x * rep(Pf(',') * x))
+end
+
+--- @param x vim.lpeg.Pattern
+local function comma(x)
+  return opt(comma1(x))
+end
+
+--- @type table<string,vim.lpeg.Pattern>
+local v = setmetatable({}, {
+  __index = function(_, k)
+    return lpeg.V(k)
+  end,
+})
+
+local colon = Pf(':')
+local opt_exact = opt(Cg(Pf('(exact)'), 'access'))
+local access = P('private') + P('protected') + P('package')
+local caccess = Cg(access, 'access')
+local desc_delim = Sf '#:' + ws
+local desc = Cg(rep(any), 'desc')
+local opt_desc = opt(desc_delim * desc)
+local cname = Cg(ident, 'name')
+local opt_parent = opt(colon * Cg(ident, 'parent'))
+
+--- @class nvim.luacats.Param
+--- @field kind 'param'
+--- @field name string
+--- @field type string
+--- @field desc? string
+
+--- @class nvim.luacats.Return
+--- @field kind 'return'
+--- @field [integer] { type: string, name?: string}
+--- @field desc? string
+
+--- @class nvim.luacats.Generic
+--- @field kind 'generic'
+--- @field name string
+--- @field type? string
+
+--- @class nvim.luacats.Class
+--- @field kind 'class'
+--- @field name string
+--- @field parent? string
+--- @field access? 'private'|'protected'|'package'
+
+--- @class nvim.luacats.Field
+--- @field kind 'field'
+--- @field name string
+--- @field type string
+--- @field desc? string
+--- @field access? 'private'|'protected'|'package'
+
+--- @class nvim.luacats.Note
+--- @field desc? string
+
+--- @alias nvim.luacats.grammar.result
+--- | nvim.luacats.Param
+--- | nvim.luacats.Return
+--- | nvim.luacats.Generic
+--- | nvim.luacats.Class
+--- | nvim.luacats.Field
+--- | nvim.luacats.Note
+
+--- @class nvim.luacats.grammar
+--- @field match fun(self, input: string): nvim.luacats.grammar.result?
+
+local function annot(nm, pat)
+  if type(nm) == 'string' then
+    nm = P(nm)
+  end
+  if pat then
+    return Ct(Cg(P(nm), 'kind') * fill * pat)
+  end
+  return Ct(Cg(P(nm), 'kind'))
+end
+
+local grammar = P {
+  rep1(P('@') * (v.ats + v.ext_ats)),
+
+  ats = annot('param', Cg(lname, 'name') * ws * v.ctype * opt_desc)
+    + annot('return', comma1(Ct(v.ctype * opt(ws * cname))) * opt_desc)
+    + annot('type', comma1(Ct(v.ctype)) * opt_desc)
+    + annot('cast', cname * ws * opt(Sf('+-')) * v.ctype)
+    + annot('generic', cname * opt(colon * v.ctype))
+    + annot('class', opt_exact * opt(paren(caccess)) * fill * cname * opt_parent)
+    + annot('field', opt(caccess * ws) * v.field_name * ws * v.ctype * opt_desc)
+    + annot('operator', cname * opt(paren(Cg(v.ltype, 'argtype'))) * colon * v.ctype)
+    + annot(access)
+    + annot('deprecated')
+    + annot('alias', cname * opt(ws * v.ctype))
+    + annot('enum', cname)
+    + annot('overload', v.ctype)
+    + annot('see', opt(desc_delim) * desc)
+    + annot('diagnostic', opt(desc_delim) * desc)
+    + annot('meta'),
+
+  --- Custom extensions
+  ext_ats = (
+    annot('note', desc)
+    + annot('since', desc)
+    + annot('nodoc')
+    + annot('inlinedoc')
+    + annot('brief', desc)
+  ),
+
+  field_name = Cg(lname + (v.ty_index * opt(P('?'))), 'name'),
+
+  ctype = parenOpt(Cg(v.ltype, 'type')),
+  ltype = parenOpt(v.ty_union),
+
+  ty_union = v.ty_opt * rep(Pf('|') * v.ty_opt),
+  ty = v.ty_fun + ident + v.ty_table + literal + paren(v.ty),
+  ty_param = Pf('<') * comma1(v.ltype) * fill * P('>'),
+  ty_opt = v.ty * opt(v.ty_param) * opt(P('[]')) * opt(P('?')),
+  ty_index = (Pf('[') * (v.ltype + ident + rep1(num)) * fill * P(']')),
+  table_key = v.ty_index + lname,
+  table_elem = v.table_key * colon * v.ltype,
+  ty_table = Pf('{') * comma1(v.table_elem) * fill * P('}'),
+  fun_param = lname * opt(colon * v.ltype),
+  ty_fun = Pf('fun') * paren(comma(lname * opt(colon * v.ltype))) * opt(colon * comma1(v.ltype)),
+}
+
+return grammar --[[@as nvim.luacats.grammar]]