treerack/context.go

package treerack

import (
	"errors"
	"io"
	"strings"
	"unicode"
)

type context struct {
	reader         io.RuneReader
	keywords       []parser
	offset         int
	readOffset     int
	consumed       int
	offsetLimit    int
	failOffset     int
	failingParser  parser
	readErr        error
	eof            bool
	results        *results
	tokens         []rune
	matchLast      bool
	level          int
	tr             []TraceEntry
	maxTraceLength int
}

func newContext(r io.RuneReader, keywords []parser, maxTraceLength int) *context {
	return &context{
		reader:         r,
		keywords:       keywords,
		results:        &results{},
		offsetLimit:    -1,
		failOffset:     -1,
		maxTraceLength: maxTraceLength,
	}
}

func (c *context) read() bool {
	if c.eof || c.readErr != nil {
		return false
	}

	token, n, err := c.reader.ReadRune()
	if err != nil {
		if errors.Is(err, io.EOF) {
			if n == 0 {
				c.eof = true
				return false
			}
		} else {
			c.readErr = err
			return false
		}
	}

	c.readOffset++

	if token == unicode.ReplacementChar {
		c.readErr = ErrInvalidUnicodeCharacter
		return false
	}

	c.tokens = append(c.tokens, token)
	return true
}

func (c *context) token() (rune, bool) {
	if c.offset == c.offsetLimit {
		return 0, false
	}

	if c.offset == c.readOffset {
		if !c.read() {
			return 0, false
		}
	}

	return c.tokens[c.offset], true
}

func (c *context) fromResults(p parser) bool {
	to, m, ok := c.results.longestResult(c.offset, p.nodeID())
	if !ok {
		return false
	}

	if m {
		c.success(to)
	} else {
		c.fail(c.offset)
	}

	return true
}

func (c *context) isKeyword(from, to int) bool {
	ol := c.offsetLimit
	c.offsetLimit = to
	defer func() { c.offsetLimit = ol }()
	for _, kw := range c.keywords {
		c.offset = from
		kw.parse(c)
		if c.matchLast && c.offset == to {
			return true
		}
	}

	return false
}

func (c *context) success(to int) {
	c.offset = to
	c.matchLast = true
	if to > c.consumed {
		c.consumed = to
	}
}

func (c *context) fail(offset int) {
	c.offset = offset
	c.matchLast = false
}

func findLine(tokens []rune, offset int) (line, column int) {
	if offset < 0 {
		return 0, 0
	}

	tokens = tokens[:offset]
	for i := range tokens {
		column++
		if tokens[i] == '\n' {
			column = 0
			line++
		}
	}

	return
}

func (c *context) parseError(p parser, unexpectedInput bool, root int) error {
	definition := p.nodeName()
	flagIndex := strings.Index(definition, ":")
	if flagIndex > 0 {
		definition = definition[:flagIndex]
	}

	if c.failingParser == nil {
		c.failOffset = c.consumed
	}

	line, col := findLine(c.tokens, c.failOffset)
	ueLine, ueCol := -1, -1
	if unexpectedInput {
		to, _, _ := c.results.longestResult(0, root)
		ueLine, ueCol = findLine(c.tokens, to)
	}

	for i := range c.tr {
		c.tr[i].FromLine, c.tr[i].FromCol = findLine(c.tokens, c.tr[i].From)
		c.tr[i].ToLine, c.tr[i].ToCol = findLine(c.tokens, c.tr[i].To)
	}

	return &ParseError{
		inputContent:        c.tokens,
		Offset:              c.failOffset,
		Line:                line,
		Column:              col,
		Definition:          definition,
		Trace:               c.tr,
		UnexpectedInputLine: ueLine,
		UnexpectedInputCol:  ueCol,
	}
}

func (c *context) finalizeParse(root parser) error {
	fp := c.failingParser
	if fp == nil {
		fp = root
	}

	to, match, found := c.results.longestResult(0, root.nodeID())
	if !found || !match || found && match && to < c.readOffset {
		return c.parseError(fp, found && match && to < c.readOffset, root.nodeID())
	}

	c.read()
	if c.eof {
		return nil
	}

	if c.readErr != nil {
		return c.readErr
	}

	return c.parseError(root, false, root.nodeID())
}

func (c *context) trace(p parser, from, to int, event TraceEvent, reason ...string) {
	if c.maxTraceLength <= 0 {
		return
	}

	if p.commitType()&userDefined == 0 || p.commitType()&FailPass != 0 {
		return
	}

	if len(c.tr) == c.maxTraceLength {
		c.tr = c.tr[1:]
	}

	switch event {
	case Success, Fail:
		c.level--
	}

	c.tr = append(c.tr, TraceEntry{
		Level:  c.level,
		Parser: p.nodeName(),
		From:   from,
		To:     to,
		Event:  event,
		Reason: strings.Join(reason, "; "),
	})

	switch event {
	case Enter:
		c.level++
	}
}