// Copyright 2018 The CUE Authors
//
// 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 load

import (
	"io/ioutil"
	"path/filepath"
	"strings"
	"unicode"

	"cuelang.org/go/cue/build"
	"cuelang.org/go/cue/errors"
	"cuelang.org/go/cue/token"
)

// matchFile determines whether the file with the given name in the given directory
// should be included in the package being constructed.
// It returns the data read from the file.
// If returnImports is true and name denotes a CUE file, matchFile reads
// until the end of the imports (and returns that data) even though it only
// considers text until the first non-comment.
// If allTags is non-nil, matchFile records any encountered build tag
// by setting allTags[tag] = true.
func matchFile(cfg *Config, file *build.File, returnImports, allFiles bool, allTags map[string]bool) (match bool, data []byte, err errors.Error) {
	if fi := cfg.fileSystem.getOverlay(file.Filename); fi != nil {
		if fi.file != nil {
			file.Source = fi.file
		} else {
			file.Source = fi.contents
		}
	}

	if file.Encoding != build.CUE {
		return
	}

	if file.Filename == "-" {
		b, err2 := ioutil.ReadAll(cfg.stdin())
		if err2 != nil {
			err = errors.Newf(token.NoPos, "read stdin: %v", err)
			return
		}
		file.Source = b
		data = b
		match = true // don't check shouldBuild for stdin
		return
	}

	name := filepath.Base(file.Filename)
	if !cfg.filesMode && strings.HasPrefix(name, ".") {
		return
	}

	if strings.HasPrefix(name, "_") {
		return
	}

	f, err := cfg.fileSystem.openFile(file.Filename)
	if err != nil {
		return
	}

	data, err = readImports(f, false, nil)
	f.Close()
	if err != nil {
		err = errors.Newf(token.NoPos, "read %s: %v", file.Filename, err)
		return
	}

	match = true
	return
}

// doMatch reports whether the name is one of:
//
//	tag (if tag is listed in cfg.Build.BuildTags or cfg.Build.ReleaseTags)
//	!tag (if tag is not listed in cfg.Build.BuildTags or cfg.Build.ReleaseTags)
//	a comma-separated list of any of these
//
func doMatch(cfg *Config, name string, allTags map[string]bool) bool {
	if name == "" {
		if allTags != nil {
			allTags[name] = true
		}
		return false
	}
	if i := strings.Index(name, ","); i >= 0 {
		// comma-separated list
		ok1 := doMatch(cfg, name[:i], allTags)
		ok2 := doMatch(cfg, name[i+1:], allTags)
		return ok1 && ok2
	}
	if strings.HasPrefix(name, "!!") { // bad syntax, reject always
		return false
	}
	if strings.HasPrefix(name, "!") { // negation
		return len(name) > 1 && !doMatch(cfg, name[1:], allTags)
	}

	if allTags != nil {
		allTags[name] = true
	}

	// Tags must be letters, digits, underscores or dots.
	// Unlike in CUE identifiers, all digits are fine (e.g., "386").
	for _, c := range name {
		if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' {
			return false
		}
	}

	// other tags
	for _, tag := range cfg.BuildTags {
		if tag == name {
			return true
		}
	}
	for _, tag := range cfg.releaseTags {
		if tag == name {
			return true
		}
	}

	return false
}