expression.go

// Copyright (C) 2017, Pablo Lalloni <plalloni@gmail.com>.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
//    this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

package seared

import (
	"github.com/lalloni/seared/buffer"
)

// Expression is a PEG parsing expression
type Expression interface {
	Name() string
	Apply(input buffer.Buffer, position int) (result *Result)
	Expectation() string
}

type expression struct {
	Expression
	name        string
	expectation string
	parser      *Parser
	matcher     Matcher
}

func newExpression(name, expectation string, p *Parser, m Matcher) *expression {
	return &expression{
		name:        name,
		expectation: expectation,
		matcher:     m,
		parser:      p,
	}
}

func (r *expression) Name() string {
	return r.name
}

func (r *expression) Expectation() string {
	return r.expectation
}

func (r *expression) Apply(input buffer.Buffer, pos int) (result *Result) {
	return r.matcher(input, pos)
}