-- 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
