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parse.go
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parse.go
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// Copyright 2015 Light Code Labs, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package casketfile
import (
"io"
"log"
"os"
"path/filepath"
"strings"
)
// Parse parses the input just enough to group tokens, in
// order, by server block. No further parsing is performed.
// Server blocks are returned in the order in which they appear.
// Directives that do not appear in validDirectives will cause
// an error. If you do not want to check for valid directives,
// pass in nil instead.
func Parse(filename string, input io.Reader, validDirectives []string) ([]ServerBlock, error) {
p := parser{Dispenser: NewDispenser(filename, input), validDirectives: validDirectives}
return p.parseAll()
}
// allTokens lexes the entire input, but does not parse it.
// It returns all the tokens from the input, unstructured
// and in order.
func allTokens(input io.Reader) ([]Token, error) {
l := new(lexer)
err := l.load(input)
if err != nil {
return nil, err
}
var tokens []Token
for l.next() {
tokens = append(tokens, l.token)
}
return tokens, nil
}
type parser struct {
Dispenser
block ServerBlock // current server block being parsed
validDirectives []string // a directive must be valid or it's an error
eof bool // if we encounter a valid EOF in a hard place
definedSnippets map[string][]Token
}
func (p *parser) parseAll() ([]ServerBlock, error) {
var blocks []ServerBlock
for p.Next() {
err := p.parseOne()
if err != nil {
return blocks, err
}
if len(p.block.Keys) > 0 {
blocks = append(blocks, p.block)
}
}
return blocks, nil
}
func (p *parser) parseOne() error {
p.block = ServerBlock{Tokens: make(map[string][]Token)}
return p.begin()
}
func (p *parser) begin() error {
if len(p.tokens) == 0 {
return nil
}
err := p.addresses()
if err != nil {
return err
}
if p.eof {
// this happens if the Casketfile consists of only
// a line of addresses and nothing else
return nil
}
if ok, name := p.isSnippet(); ok {
if p.definedSnippets == nil {
p.definedSnippets = map[string][]Token{}
}
if _, found := p.definedSnippets[name]; found {
return p.Errf("redeclaration of previously declared snippet %s", name)
}
// consume all tokens til matched close brace
tokens, err := p.snippetTokens()
if err != nil {
return err
}
p.definedSnippets[name] = tokens
// empty block keys so we don't save this block as a real server.
p.block.Keys = nil
return nil
}
return p.blockContents()
}
func (p *parser) addresses() error {
var expectingAnother bool
for {
tkn := replaceEnvVars(p.Val())
// special case: import directive replaces tokens during parse-time
if tkn == "import" && p.isNewLine() {
err := p.doImport()
if err != nil {
return err
}
continue
}
// Open brace definitely indicates end of addresses
if tkn == "{" {
if expectingAnother {
return p.Errf("Expected another address but had '%s' - check for extra comma", tkn)
}
break
}
if tkn != "" { // empty token possible if user typed ""
// Trailing comma indicates another address will follow, which
// may possibly be on the next line
if tkn[len(tkn)-1] == ',' {
tkn = tkn[:len(tkn)-1]
expectingAnother = true
} else {
expectingAnother = false // but we may still see another one on this line
}
p.block.Keys = append(p.block.Keys, tkn)
}
// Advance token and possibly break out of loop or return error
hasNext := p.Next()
if expectingAnother && !hasNext {
return p.EOFErr()
}
if !hasNext {
p.eof = true
break // EOF
}
if !expectingAnother && p.isNewLine() {
break
}
}
return nil
}
func (p *parser) blockContents() error {
errOpenCurlyBrace := p.openCurlyBrace()
if errOpenCurlyBrace != nil {
// single-server configs don't need curly braces
p.cursor--
}
err := p.directives()
if err != nil {
return err
}
// Only look for close curly brace if there was an opening
if errOpenCurlyBrace == nil {
err = p.closeCurlyBrace()
if err != nil {
return err
}
}
return nil
}
// directives parses through all the lines for directives
// and it expects the next token to be the first
// directive. It goes until EOF or closing curly brace
// which ends the server block.
func (p *parser) directives() error {
for p.Next() {
// end of server block
if p.Val() == "}" {
break
}
// special case: import directive replaces tokens during parse-time
if p.Val() == "import" {
err := p.doImport()
if err != nil {
return err
}
p.cursor-- // cursor is advanced when we continue, so roll back one more
continue
}
// normal case: parse a directive on this line
if err := p.directive(); err != nil {
return err
}
}
return nil
}
// doImport swaps out the import directive and its argument
// (a total of 2 tokens) with the tokens in the specified file
// or globbing pattern. When the function returns, the cursor
// is on the token before where the import directive was. In
// other words, call Next() to access the first token that was
// imported.
func (p *parser) doImport() error {
// syntax checks
if !p.NextArg() {
return p.ArgErr()
}
importPattern := replaceEnvVars(p.Val())
if importPattern == "" {
return p.Err("Import requires a non-empty filepath")
}
if p.NextArg() {
return p.Err("Import takes only one argument (glob pattern or file)")
}
// splice out the import directive and its argument (2 tokens total)
tokensBefore := p.tokens[:p.cursor-1]
tokensAfter := p.tokens[p.cursor+1:]
var importedTokens []Token
// first check snippets. That is a simple, non-recursive replacement
if p.definedSnippets != nil && p.definedSnippets[importPattern] != nil {
importedTokens = p.definedSnippets[importPattern]
} else {
// make path relative to the file of the _token_ being processed rather
// than current working directory (issue #867) and then use glob to get
// list of matching filenames
absFile, err := filepath.Abs(p.Dispenser.File())
if err != nil {
return p.Errf("Failed to get absolute path of file: %s: %v", p.Dispenser.filename, err)
}
var matches []string
var globPattern string
if !filepath.IsAbs(importPattern) {
globPattern = filepath.Join(filepath.Dir(absFile), importPattern)
} else {
globPattern = importPattern
}
if strings.Count(globPattern, "*") > 1 || strings.Count(globPattern, "?") > 1 ||
(strings.Contains(globPattern, "[") && strings.Contains(globPattern, "]")) {
// See issue #2096 - a pattern with many glob expansions can hang for too long
return p.Errf("Glob pattern may only contain one wildcard (*), but has others: %s", globPattern)
}
matches, err = filepath.Glob(globPattern)
if err != nil {
return p.Errf("Failed to use import pattern %s: %v", importPattern, err)
}
if len(matches) == 0 {
if strings.ContainsAny(globPattern, "*?[]") {
log.Printf("[WARNING] No files matching import glob pattern: %s", importPattern)
} else {
return p.Errf("File to import not found: %s", importPattern)
}
}
// collect all the imported tokens
for _, importFile := range matches {
newTokens, err := p.doSingleImport(importFile)
if err != nil {
return err
}
importedTokens = append(importedTokens, newTokens...)
}
}
// splice the imported tokens in the place of the import statement
// and rewind cursor so Next() will land on first imported token
p.tokens = append(tokensBefore, append(importedTokens, tokensAfter...)...)
p.cursor--
return nil
}
// doSingleImport lexes the individual file at importFile and returns
// its tokens or an error, if any.
func (p *parser) doSingleImport(importFile string) ([]Token, error) {
file, err := os.Open(importFile)
if err != nil {
return nil, p.Errf("Could not import %s: %v", importFile, err)
}
defer file.Close()
if info, err := file.Stat(); err != nil {
return nil, p.Errf("Could not import %s: %v", importFile, err)
} else if info.IsDir() {
return nil, p.Errf("Could not import %s: is a directory", importFile)
}
importedTokens, err := allTokens(file)
if err != nil {
return nil, p.Errf("Could not read tokens while importing %s: %v", importFile, err)
}
// Tack the file path onto these tokens so errors show the imported file's name
// (we use full, absolute path to avoid bugs: issue #1892)
filename, err := filepath.Abs(importFile)
if err != nil {
return nil, p.Errf("Failed to get absolute path of file: %s: %v", p.Dispenser.filename, err)
}
for i := 0; i < len(importedTokens); i++ {
importedTokens[i].File = filename
}
return importedTokens, nil
}
// directive collects tokens until the directive's scope
// closes (either end of line or end of curly brace block).
// It expects the currently-loaded token to be a directive
// (or } that ends a server block). The collected tokens
// are loaded into the current server block for later use
// by directive setup functions.
func (p *parser) directive() error {
dir := replaceEnvVars(p.Val())
nesting := 0
// TODO: More helpful error message ("did you mean..." or "maybe you need to install its server type")
if !p.validDirective(dir) {
return p.Errf("Unknown directive '%s'", dir)
}
// The directive itself is appended as a relevant token
p.block.Tokens[dir] = append(p.block.Tokens[dir], p.tokens[p.cursor])
for p.Next() {
if p.Val() == "{" {
nesting++
} else if p.isNewLine() && nesting == 0 {
p.cursor-- // read too far
break
} else if p.Val() == "}" && nesting > 0 {
nesting--
} else if p.Val() == "}" && nesting == 0 {
return p.Err("Unexpected '}' because no matching opening brace")
} else if p.Val() == "import" && p.isNewLine() {
if err := p.doImport(); err != nil {
return err
}
p.cursor-- // cursor is advanced when we continue, so roll back one more
continue
}
p.tokens[p.cursor].Text = replaceEnvVars(p.tokens[p.cursor].Text)
p.block.Tokens[dir] = append(p.block.Tokens[dir], p.tokens[p.cursor])
}
if nesting > 0 {
return p.EOFErr()
}
return nil
}
// openCurlyBrace expects the current token to be an
// opening curly brace. This acts like an assertion
// because it returns an error if the token is not
// a opening curly brace. It does NOT advance the token.
func (p *parser) openCurlyBrace() error {
if p.Val() != "{" {
return p.SyntaxErr("{")
}
return nil
}
// closeCurlyBrace expects the current token to be
// a closing curly brace. This acts like an assertion
// because it returns an error if the token is not
// a closing curly brace. It does NOT advance the token.
func (p *parser) closeCurlyBrace() error {
if p.Val() != "}" {
return p.SyntaxErr("}")
}
return nil
}
// validDirective returns true if dir is in p.validDirectives.
func (p *parser) validDirective(dir string) bool {
if p.validDirectives == nil {
return true
}
for _, d := range p.validDirectives {
if d == dir {
return true
}
}
return false
}
// replaceEnvVars replaces environment variables that appear in the token
// and understands both the $UNIX and %WINDOWS% syntaxes.
func replaceEnvVars(s string) string {
s = replaceEnvReferences(s, "{%", "%}")
s = replaceEnvReferences(s, "{$", "}")
return s
}
// replaceEnvReferences performs the actual replacement of env variables
// in s, given the placeholder start and placeholder end strings.
func replaceEnvReferences(s, refStart, refEnd string) string {
index := strings.Index(s, refStart)
for index != -1 {
endIndex := strings.Index(s[index:], refEnd)
if endIndex == -1 {
break
}
endIndex += index
if endIndex > index+len(refStart) {
ref := s[index : endIndex+len(refEnd)]
s = strings.Replace(s, ref, os.Getenv(ref[len(refStart):len(ref)-len(refEnd)]), -1)
} else {
return s
}
index = strings.Index(s, refStart)
}
return s
}
// ServerBlock associates any number of keys (usually addresses
// of some sort) with tokens (grouped by directive name).
type ServerBlock struct {
Keys []string
Tokens map[string][]Token
}
func (p *parser) isSnippet() (bool, string) {
keys := p.block.Keys
// A snippet block is a single key with parens. Nothing else qualifies.
if len(keys) == 1 && strings.HasPrefix(keys[0], "(") && strings.HasSuffix(keys[0], ")") {
return true, strings.TrimSuffix(keys[0][1:], ")")
}
return false, ""
}
// read and store everything in a block for later replay.
func (p *parser) snippetTokens() ([]Token, error) {
// TODO: disallow imports in snippets for simplicity at import time
// snippet must have curlies.
err := p.openCurlyBrace()
if err != nil {
return nil, err
}
count := 1
tokens := []Token{}
for p.Next() {
if p.Val() == "}" {
count--
if count == 0 {
break
}
}
if p.Val() == "{" {
count++
}
tokens = append(tokens, p.tokens[p.cursor])
}
// make sure we're matched up
if count != 0 {
return nil, p.SyntaxErr("}")
}
return tokens, nil
}