// 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

// Files in this package are to a large extent based on Go files from the following
// Go packages:
//    - cmd/go/internal/load
//    - go/build

import (
	"path/filepath"

	"cuelang.org/go/cue/build"
	"cuelang.org/go/cue/errors"
	"cuelang.org/go/cue/token"
	"cuelang.org/go/internal/mod/modpkgload"
)

type loader struct {
	cfg    *Config
	tagger *tagger
	stk    importStack
	pkgs   *modpkgload.Packages

	// dirCachedBuildFiles caches the work involved when reading a
	// directory. It is keyed by directory name. When we descend into
	// subdirectories to load patterns such as ./... we often end up
	// loading parent directories many times over; this cache
	// amortizes that work.
	dirCachedBuildFiles map[string]cachedDirFiles
}

type cachedDirFiles struct {
	err       errors.Error
	filenames []string
}

func newLoader(c *Config, tg *tagger, pkgs *modpkgload.Packages) *loader {
	return &loader{
		cfg:                 c,
		tagger:              tg,
		pkgs:                pkgs,
		dirCachedBuildFiles: make(map[string]cachedDirFiles),
	}
}

func (l *loader) abs(filename string) string {
	if !isLocalImport(filename) {
		return filename
	}
	return filepath.Join(l.cfg.Dir, filename)
}

func (l *loader) errPkgf(importPos []token.Pos, format string, args ...interface{}) *PackageError {
	err := &PackageError{
		ImportStack: l.stk.Copy(),
		Message:     errors.NewMessagef(format, args...),
	}
	err.fillPos(l.cfg.Dir, importPos)
	return err
}

// cueFilesPackage creates a package for building a collection of CUE files
// (typically named on the command line).
func (l *loader) cueFilesPackage(files []*build.File) *build.Instance {
	// ModInit() // TODO: support modules
	pkg := l.cfg.Context.NewInstance(l.cfg.Dir, nil)

	for _, bf := range files {
		f := bf.Filename
		if f == "-" {
			continue
		}
		if !filepath.IsAbs(f) {
			f = filepath.Join(l.cfg.Dir, f)
		}
		fi, err := l.cfg.fileSystem.stat(f)
		if err != nil {
			return l.cfg.newErrInstance(errors.Wrapf(err, token.NoPos, "could not find file %v", f))
		}
		if fi.IsDir() {
			return l.cfg.newErrInstance(errors.Newf(token.NoPos, "file is a directory %v", f))
		}
	}

	fp := newFileProcessor(l.cfg, pkg, l.tagger)
	if l.cfg.Package == "*" {
		fp.allPackages = true
		pkg.PkgName = "_"
	}
	for _, bf := range files {
		fp.add(l.cfg.Dir, bf, allowAnonymous|allowExcludedFiles)
	}

	// TODO: ModImportFromFiles(files)
	pkg.Dir = l.cfg.Dir
	rewriteFiles(pkg, pkg.Dir, true)
	for _, err := range errors.Errors(fp.finalize(pkg)) { // ImportDir(&ctxt, dir, 0)
		var x *NoFilesError
		if len(pkg.OrphanedFiles) == 0 || !errors.As(err, &x) {
			pkg.ReportError(err)
		}
	}
	// TODO: Support module importing.
	// if ModDirImportPath != nil {
	// 	// Use the effective import path of the directory
	// 	// for deciding visibility during pkg.load.
	// 	bp.ImportPath = ModDirImportPath(dir)
	// }

	pkg.User = true
	l.addFiles(pkg)

	_ = pkg.Complete()
	pkg.DisplayPath = "command-line-arguments"

	return pkg
}

// addFiles populates p.Files by reading CUE syntax from p.BuildFiles.
func (l *loader) addFiles(p *build.Instance) {
	for _, bf := range p.BuildFiles {
		f, err := l.cfg.fileSystem.getCUESyntax(bf)
		if err != nil {
			p.ReportError(errors.Promote(err, "load"))
		}
		_ = p.AddSyntax(f)
	}
}
