-- Copyright 2006-2025 Mitchell. See LICENSE.
-- templ LPeg lexer.

local lexer = lexer
local starts_line = lexer.starts_line
local P, S = lpeg.P, lpeg.S

local lex = lexer.new(..., {inherit = lexer.load('go')})

local close_paren = lex:tag(lexer.OPERATOR, P(')'))
local open_brace = lex:tag(lexer.OPERATOR, P('{'))
local close_brace = lex:tag(lexer.OPERATOR, P('}'))
local colon = lex:tag(lexer.OPERATOR, P(':'))
local at = lex:tag(lexer.OPERATOR, P('@'))
local ws = lex:get_rule('whitespace')
local ident = lex:get_rule('identifier')

local html = lexer.load('html')
local go_expr = lexer.load('go', 'go.expr')
local go_stmt1 = lexer.load('go', 'go.stmt1')
local go_stmt2 = lexer.load('go', 'go.stmt2')
local go_stmt3 = lexer.load('go', 'go.stmt3')
local for_ = lex:tag(lexer.KEYWORD, lexer.word_match('for if switch'))
local else_ = close_brace * ws^0 * lex:tag(lexer.KEYWORD, P('else'))
local case_ = lex:tag(lexer.KEYWORD, lexer.word_match('case default'))
html:embed(go_expr, open_brace, close_brace * close_brace^-1)
html:embed(go_stmt1, starts_line(for_ + else_, true), open_brace * #lexer.newline)
html:embed(go_stmt2, starts_line(case_, true), colon * #lexer.newline)
html:embed(go_stmt3, starts_line(at, true), (ident + open_brace + close_paren) * #lexer.newline)

local func_block_start = close_paren * ws^0 * open_brace

lex:set_word_list(lexer.KEYWORD, 'templ css script', true)

local function starts_with(keyword)
	local prefix = '\n' .. keyword .. '%s'
	return function(input, index)
		local i = index - 1024
		if i < 1 then
			i = 1
		end
		local s = input:sub(i, index)
		local k = 0
		repeat
			i = s:find('\n%w', i)
			if i then
				k = i
				i = i + 2
			end
		until not i
		return k > 0 and s:find(prefix, k) and true
	end
end

lex:embed(html, func_block_start * P(starts_with("templ")), starts_line(close_brace))

local css = lexer.load('css')
local css_go_expr = lexer.load('go', 'go.expr2')
css:embed(css_go_expr, open_brace, close_brace)
lex:embed(css, func_block_start * P(starts_with("css")), starts_line(close_brace))

local js = lexer.load('javascript')
lex:embed(js, func_block_start * P(starts_with("script")), starts_line(close_brace))

return lex