package util

import (
	"go/build"
	"go/parser"
	"go/token"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
)

// IsStandardImportPath reports whether $GOROOT/src/path should be considered
// part of the standard distribution. For historical reasons we allow people to add
// their own code to $GOROOT instead of using $GOPATH, but we assume that
// code will start with a domain name (dot in the first element).
//
// Note that this function is meant to evaluate whether a directory found in GOROOT
// should be treated as part of the standard library. It should not be used to decide
// that a directory found in GOPATH should be rejected: directories in GOPATH
// need not have dots in the first element, and they just take their chances
// with future collisions in the standard library.
//
// This function was copied from src/cmd/go/internal/search/search.go in Go's code.
func isStandardImportPath(path string) bool {
	i := strings.Index(path, "/")
	if i < 0 {
		i = len(path)
	}
	elem := path[:i]
	return !strings.Contains(elem, ".")
}

// Ignore specifies a set of resources to ignore
type Ignore struct {
	Dirs    []string
	Trees   []string
	Regexes []*regexp.Regexp
}

func (ignore *Ignore) ignore(path string) bool {
	if ignore == nil {
		return false
	}
	for _, re := range ignore.Regexes {
		if re.MatchString(path) {
			return true
		}
	}

	for _, dir := range ignore.Trees {
		if strings.HasPrefix(path+"/", dir+"/") {
			return true
		}
	}

	for _, dir := range ignore.Dirs {
		if path == dir {
			return true
		}
	}
	return false
}

type PackageInfoCollector struct {
	packageInfos   map[string]*build.Package
	mainFiles      map[string][]string
	packagePath    string
	ignore         *Ignore
	includeMD      bool
	extensions     []string
	otherResources *OtherResources
	isStdPackages  map[string]bool
}

type OtherResources struct {
	ProtoFiles []string
	TmplFiles  []string
	MDFiles    []string
	SFiles     []string
	Other      []string
}

func NewPackageInfoCollector(ignore *Ignore, includeMD bool, extensions []string) *PackageInfoCollector {
	return &PackageInfoCollector{
		packageInfos:  make(map[string]*build.Package),
		mainFiles:     make(map[string][]string),
		isStdPackages: make(map[string]bool),
		ignore:        ignore,
		includeMD:     includeMD,
		extensions:    extensions,
	}
}

func (p *PackageInfoCollector) isStandardPackage(pkg *build.Package) bool {
	return pkg.Goroot && pkg.ImportPath != "" && isStandardImportPath(pkg.ImportPath)
}

func (p *PackageInfoCollector) isStandard(pkg string) (bool, error) {
	if is, exists := p.isStdPackages[pkg]; exists {
		return is, nil
	}
	pkgInfo, err := build.Import(pkg, "", build.IgnoreVendor)
	if err != nil {
		return false, err
	}

	p.isStdPackages[pkg] = p.isStandardPackage(pkgInfo)

	return p.isStdPackages[pkg], nil
}

func (p *PackageInfoCollector) resolveImports(baseDir string, imports []string) []string {
	var paths []string
	for _, importPath := range imports {
		importedPackage, err := build.Import(importPath, baseDir, 0)
		if err == nil {
			paths = append(paths, importedPackage.ImportPath)
		} else {
			// Just assume we haven't 'go get'd it yet.
			paths = append(paths, importPath)
		}
	}
	return paths
}

func (p *PackageInfoCollector) CollectPackageInfos(packagePath string) error {
	pkg, err := build.Import(packagePath, "", build.IgnoreVendor)
	if err != nil {
		// Don't worry about lack of Go files; there may be Go files in
		// subdirectories.  We just want to find the absolute path in
		// GOPATH/GOROOT, but return error if not found at all.
		if _, ok := err.(*build.NoGoError); !ok {
			return err
		}
	}

	p.otherResources = &OtherResources{}

	if err := filepath.Walk(pkg.Dir+"/", func(path string, info os.FileInfo, err error) error {
		if !info.IsDir() {
			// Cited from https://golang.org/cmd/go/#hdr-Package_lists:
			//   Directory and file names that begin with "." or "_" are ignored
			//   by the go tool, as are directories named "testdata".
			if base := filepath.Base(path); base[0] == '.' || base[0] == '_' {
				return nil
			}
			for _, ext := range p.extensions {
				if ext[0] != '.' {
					ext = "." + ext
				}
				if strings.HasSuffix(path, ext) {
					switch ext {
					case ".proto":
						p.otherResources.ProtoFiles = append(p.otherResources.ProtoFiles, path)
					case ".md":
						p.otherResources.MDFiles = append(p.otherResources.MDFiles, path)
					case ".s":
						p.otherResources.SFiles = append(p.otherResources.SFiles, path)
					default:
						p.otherResources.Other = append(p.otherResources.Other, path)
					}
				}
			}
			return nil
		}

		relPath := path[len(pkg.SrcRoot)+1:]
		if strings.HasSuffix(relPath, "/") {
			relPath = relPath[:len(relPath)-1]
		}

		// Cited from https://golang.org/cmd/go/#hdr-Package_lists:
		//   Directory and file names that begin with "." or "_" are ignored
		//   by the go tool, as are directories named "testdata".
		if base := filepath.Base(relPath); base[0] == '.' || base[0] == '_' || base == "testdata" || base == "vendor" {
			return filepath.SkipDir
		}

		if p.ignore.ignore(relPath) {
			return nil
		}

		pkgInfo, err := build.ImportDir(path, build.IgnoreVendor)
		if err != nil {
			if _, ok := err.(*build.NoGoError); ok {
				return nil
			}
			panic(err)
		}

		if len(pkgInfo.GoFiles) > 0 || len(pkgInfo.CgoFiles) > 0 {
			// Show vendor-expanded paths in listing
			pkgInfo.TestImports = p.resolveImports(pkg.Dir, pkgInfo.TestImports)
			pkgInfo.XTestImports = p.resolveImports(pkg.Dir, pkgInfo.XTestImports)

			p.packageInfos[relPath] = pkgInfo
		}

		return nil
	}); err != nil {
		return err
	}

	p.packagePath = packagePath
	return nil
}

func (p *PackageInfoCollector) BuildArtifact() (*ProjectData, error) {
	data := &ProjectData{}
	var err error

	// Get provided packages
	if data.Packages, err = p.BuildPackageTree(false, false, false); err != nil {
		return nil, err
	}
	sort.Strings(data.Packages)

	// Get imported packages
	data.Dependencies = make(map[string][]string)
	for pkgName, info := range p.packageInfos {
		data.Dependencies[pkgName] = []string{}
		for _, item := range info.Imports {
			if pos := strings.LastIndex(item, "/vendor/"); pos != -1 {
				item = item[pos+8:]
			}
			if is, _ := p.isStandard(item); !is {
				data.Dependencies[pkgName] = append(data.Dependencies[pkgName], item)
			}
		}
	}

	// Get tests
	data.Tests = make(map[string][]string)
	for pkgName, pkgInfo := range p.packageInfos {
		if len(pkgInfo.TestGoFiles) > 0 {
			data.Tests[pkgName] = []string{}
			for _, item := range pkgInfo.TestImports {
				if is, _ := p.isStandard(item); !is {
					data.Tests[pkgName] = append(data.Tests[pkgName], item)
				}
			}
			for _, item := range pkgInfo.XTestImports {
				if is, _ := p.isStandard(item); !is {
					data.Tests[pkgName] = append(data.Tests[pkgName], item)
				}
			}
		}
	}

	// Get main files
	data.MainFiles = make(map[string][]string)
	for pkgName, item := range p.mainFiles {
		data.MainFiles[pkgName] = []string{}
		for _, dep := range item {
			if is, _ := p.isStandard(dep); !is {
				data.MainFiles[pkgName] = append(data.MainFiles[pkgName], dep)
			}
		}
	}

	return data, nil
}

func (p *PackageInfoCollector) CollectInstalledResources() ([]string, error) {
	var resources []string

	for _, info := range p.packageInfos {
		resources = append(resources, info.Dir)

		allFileLists := [][]string{
			info.GoFiles, info.IgnoredGoFiles, info.CgoFiles,
			info.CFiles, info.CXXFiles, info.MFiles, info.HFiles, info.FFiles,
			info.SFiles, info.SwigFiles, info.SwigCXXFiles, info.SysoFiles,
			info.TestGoFiles, info.XTestGoFiles}
		for _, fileList := range allFileLists {
			for _, file := range fileList {
				resources = append(resources, path.Join(info.Dir, file))
			}
		}
	}

	if p.otherResources.ProtoFiles != nil {
		resources = append(resources, p.otherResources.ProtoFiles...)
	}
	if p.includeMD && p.otherResources.MDFiles != nil {
		resources = append(resources, p.otherResources.MDFiles...)
	}
	if p.otherResources.SFiles != nil {
		resources = append(resources, p.otherResources.SFiles...)
	}
	if p.otherResources.Other != nil {
		resources = append(resources, p.otherResources.Other...)
	}

	return resources, nil
}

func (p *PackageInfoCollector) CollectProjectDeps(standard, skipSelf, withTests, testsOnly bool) ([]string, error) {
	imports := make(map[string]struct{})

	for _, info := range p.packageInfos {
		var pkgImports []string
		if testsOnly {
			pkgImports = append(info.TestImports, info.XTestImports...)
		} else if withTests {
			pkgImports = append(info.Imports, info.TestImports...)
			pkgImports = append(pkgImports, info.XTestImports...)
		} else {
			pkgImports = info.Imports
		}
		for _, item := range pkgImports {
			if item == "C" {
				continue
			}
			if pos := strings.LastIndex(item, "/vendor/"); pos != -1 {
				item = item[pos+8:]
			}
			if _, ok := imports[item]; !ok {
				imports[item] = struct{}{}
			}
		}
	}

	var pkgs []string

	for relPath := range imports {
		if skipSelf && strings.HasPrefix(relPath, p.packagePath) {
			continue
		}

		if p.ignore.ignore(relPath) {
			continue
		}

		pkgInfo, err := build.Import(relPath, "", build.IgnoreVendor)
		// assuming the stdlib is always processed properly
		if !standard && err == nil && p.isStandardPackage(pkgInfo) {
			continue
		}

		pkgs = append(pkgs, relPath)
	}

	return pkgs, nil
}

func (p *PackageInfoCollector) BuildPackageTree(includeMain, withTests, testsOnly bool) ([]string, error) {
	// TODO(jchaloup): strip all main package unless explicitely requested
	var entryPoints []string
	if testsOnly || withTests {
		for p, pkgInfo := range p.packageInfos {
			if len(pkgInfo.TestGoFiles) > 0 || len(pkgInfo.XTestGoFiles) > 0 {
				entryPoints = append(entryPoints, p)
			}
		}
		if testsOnly {
			return entryPoints, nil
		}
	}

	for pkgName, pkgInfo := range p.packageInfos {
		// check package name of each file
		var nonMainFiles []string
		files := pkgInfo.GoFiles
		files = append(files, pkgInfo.CgoFiles...)
		for _, file := range files {
			f, err := parser.ParseFile(token.NewFileSet(), path.Join(pkgInfo.Dir, file), nil, 0)
			if err != nil {
				return nil, err
			}
			if f.Name.Name == "main" && file != "doc.go" {
				importsList := make([]string, 0)
				for _, i := range f.Imports {
					importsList = append(importsList, i.Path.Value[1:len(i.Path.Value)-1])
				}
				p.mainFiles[path.Join(pkgInfo.ImportPath, file)] = importsList
			}

			if !includeMain && f.Name.Name == "main" {
				continue
			}
			nonMainFiles = append(nonMainFiles, file)
		}
		if len(nonMainFiles) > 0 {
			entryPoints = append(entryPoints, pkgName)
		}
	}

	return entryPoints, nil
}

type ProjectData struct {
	Packages     []string            `json:"packages"`
	Dependencies map[string][]string `json:"dependencies"`
	Tests        map[string][]string `json:"tests"`
	MainFiles    map[string][]string `json:"main"`
}