-- Copyright 2006-2023 Mitchell. See LICENSE.
-- Ruby LPeg lexer.
local lexer = lexer
local P, S = lpeg.P, lpeg.S

local lex = lexer.new(...)

-- Keywords.
lex:add_rule('keyword', lex:tag(lexer.KEYWORD, lex:word_match(lexer.KEYWORD)))

-- Functions.
local builtin_func = lex:tag(lexer.FUNCTION_BUILTIN,
                             lex:word_match(lexer.FUNCTION_BUILTIN))
lex:add_rule('function', -lpeg.B('.') * builtin_func * -S('.:|'))

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

-- Comments.
local line_comment = lexer.to_eol('#', true)
local block_comment = lexer.range(lexer.starts_line('=begin'),
                                  lexer.starts_line('=end'))
lex:add_rule('comment', lex:tag(lexer.COMMENT, block_comment + line_comment))

-- Strings.
local delimiter_matches = {['('] = ')', ['['] = ']', ['{'] = '}'}
local literal_delimited = P(function(input, index)
    local delimiter = input:sub(index, index)
    if not delimiter:find('[%w\r\n\f\t ]') then -- only non alpha-numerics
        local match_pos, patt
        if delimiter_matches[delimiter] then
            -- Handle nested delimiter/matches in strings.
            local s, e = delimiter, delimiter_matches[delimiter]
            patt = lexer.range(s, e, false, true, true)
        else
            patt = lexer.range(delimiter)
        end
        match_pos = lpeg.match(patt, input, index)
        return match_pos or #input + 1
    end
end)

local cmd_str = lexer.range('`')
local lit_cmd = '%x' * literal_delimited
local lit_array = '%w' * literal_delimited
local sq_str = lexer.range("'")
local dq_str = lexer.range('"')
local lit_str = '%' * S('qQ') ^ -1 * literal_delimited
local heredoc = '<<' * P(function(input, index)
    local s, e, indented, _, delimiter = input:find(
                                             '([%-~]?)(["`]?)([%a_][%w_]*)%2[\n\r\f;]+',
                                             index)
    if s == index and delimiter then
        local end_heredoc = (#indented > 0 and '[\n\r\f]+ *' or '[\n\r\f]+')
        s, e = input:find(end_heredoc .. delimiter, e)
        return e and e + 1 or #input + 1
    end
end)
local string = lex:tag(lexer.STRING,
                       (sq_str + dq_str + lit_str + heredoc + cmd_str + lit_cmd +
                           lit_array) * 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 lit_regex = '%r' * literal_delimited * S('iomx') ^ 0
local regex = lex:tag(lexer.REGEX, regex_str + lit_regex)
lex:add_rule('string', string + regex)

-- Numbers.
local numeric_literal = '?' * (lexer.any - lexer.space) * -word_char -- TODO: meta, control, etc.
lex:add_rule('number', lex:tag(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',
             lex:tag(lexer.VARIABLE, global_var + class_var + inst_var))

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

-- Operators.
lex:add_rule('operator', lex:tag(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, '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, 'case', '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, '{', '}')
lex:add_fold_point(lexer.COMMENT, '=begin', '=end')

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

lex:set_word_list(lexer.FUNCTION_BUILTIN, {
    'at_exit', 'autoload', 'binding', 'caller', 'catch', 'chop', 'chop!',
    'chomp', 'chomp!', 'eval', 'exec', 'exit', 'exit!', 'extend', 'fail',
    'fork', 'format', 'gets', 'global_variables', 'gsub', 'gsub!', 'include',
    'iterator?', 'lambda', 'load', 'local_variables', 'loop', 'module_function',
    'open', 'p', 'print', 'printf', 'proc', 'putc', 'puts', 'raise', 'rand',
    'readline', 'readlines', 'require', 'require_relative', 'select', 'sleep',
    'split', 'sprintf', 'srand', 'sub', 'sub!', 'syscall', 'system', 'test',
    'trace_var', 'trap', 'untrace_var'
})

lexer.property['scintillua.comment'] = '#'
lexer.property['scintillua.word.chars'] =
    'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_?!'

return lex
