-- Copyright 2006-2023 Mitchell. See LICENSE.
-- Copyright 2017 Michel Martens.
-- Crystal LPeg lexer (based on Ruby).

local lexer = require('lexer')
local token, word_match = lexer.token, lexer.word_match
local P, S = lpeg.P, lpeg.S

local lex = lexer.new('crystal')

-- Whitespace.
lex:add_rule('whitespace', token(lexer.WHITESPACE, lexer.space^1))

-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match{
  'alias', 'begin', 'break', 'case', 'class', 'def', 'defined?', 'do', 'else', 'elsif', 'end',
  'ensure', 'false', 'for', 'if', 'in', 'module', 'next', 'nil', 'not', 'redo', 'rescue', 'retry',
  'return', 'self', 'super', 'then', 'true', 'undef', 'unless', 'until', 'when', 'while', 'yield',
  '__FILE__', '__LINE__'
}))

-- Functions.
lex:add_rule('function', token(lexer.FUNCTION, word_match{
  'abort', 'at_exit', 'caller', 'delay', 'exit', 'fork', 'future', 'get_stack_top', 'gets', 'lazy',
  'loop', 'main', 'p', 'print', 'printf', 'puts', 'raise', 'rand', 'read_line', 'require', 'sleep',
  'spawn', 'sprintf', 'system', 'with_color',
  -- Macros.
  'assert_responds_to', 'debugger', 'parallel', 'pp', 'record', 'redefine_main'
}) * -S('.:|'))

-- Identifiers.
local word_char = lexer.alnum + S('_!?')
local word = (lexer.alpha + '_') * word_char^0
lex:add_rule('identifier', token(lexer.IDENTIFIER, word))

-- Comments.
lex:add_rule('comment', token(lexer.COMMENT, lexer.to_eol('#', true)))

-- Strings.
local cmd_str = lexer.range('`')
local sq_str = lexer.range("'")
local dq_str = lexer.range('"')
local heredoc = '<<' * P(function(input, index)
  local _, e, indented, _, delimiter = input:find('^(%-?)(["`]?)([%a_][%w_]*)%2[\n\r\f;]+', index)
  if not delimiter then return end
  local end_heredoc = (#indented > 0 and '[\n\r\f]+ *' or '[\n\r\f]+')
  _, e = input:find(end_heredoc .. delimiter, e)
  return e and e + 1 or #input + 1
end)
local string = token(lexer.STRING, (sq_str + dq_str + heredoc + cmd_str) * S('f')^-1)
-- TODO: regex_str fails with `obj.method /patt/` syntax.
local regex_str = lexer.after_set('!%^&*([{-=+|:;,?<>~', lexer.range('/', true) * S('iomx')^0)
local regex = token(lexer.REGEX, regex_str)
lex:add_rule('string', string + regex)

-- Numbers.
local numeric_literal = '?' * (lexer.any - lexer.space) * -word_char -- TODO: meta, control, etc.
lex:add_rule('number', token(lexer.NUMBER, lexer.number_('_') * S('ri')^-1 + numeric_literal))

-- Variables.
local global_var = '$' *
  (word + S('!@L+`\'=~/\\,.;<>_*"$?:') + lexer.digit + '-' * S('0FadiIKlpvw'))
local class_var = '@@' * word
local inst_var = '@' * word
lex:add_rule('variable', token(lexer.VARIABLE, global_var + class_var + inst_var))

-- Symbols.
lex:add_rule('symbol', token('symbol', ':' * P(function(input, index)
  if input:sub(index - 2, index - 2) ~= ':' then return true end
end) * (word_char^1 + sq_str + dq_str)))
lex:add_style('symbol', lexer.styles.constant)

-- Operators.
lex:add_rule('operator', token(lexer.OPERATOR, S('!%^&*()[]{}-=+/|:;.,?<>~')))

-- Fold points.
local function disambiguate(text, pos, line, s)
  return line:sub(1, s - 1):match('^%s*$') and not text:sub(1, pos - 1):match('\\[ \t]*\r?\n$') and
    1 or 0
end
lex:add_fold_point(lexer.KEYWORD, 'begin', 'end')
lex:add_fold_point(lexer.KEYWORD, 'case', 'end')
lex:add_fold_point(lexer.KEYWORD, 'class', 'end')
lex:add_fold_point(lexer.KEYWORD, 'def', 'end')
lex:add_fold_point(lexer.KEYWORD, 'do', 'end')
lex:add_fold_point(lexer.KEYWORD, 'for', 'end')
lex:add_fold_point(lexer.KEYWORD, 'module', 'end')
lex:add_fold_point(lexer.KEYWORD, 'if', disambiguate)
lex:add_fold_point(lexer.KEYWORD, 'while', disambiguate)
lex:add_fold_point(lexer.KEYWORD, 'unless', disambiguate)
lex:add_fold_point(lexer.KEYWORD, 'until', disambiguate)
lex:add_fold_point(lexer.OPERATOR, '(', ')')
lex:add_fold_point(lexer.OPERATOR, '[', ']')
lex:add_fold_point(lexer.OPERATOR, '{', '}')

lexer.property['scintillua.comment'] = '#'

return lex
