// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package internal

import (
	"path"
	"strings"
	"time"

	"github.com/google/safehtml"
	"golang.org/x/mod/module"
	"golang.org/x/pkgsite/internal/licenses"
	"golang.org/x/pkgsite/internal/source"
	"golang.org/x/pkgsite/internal/stdlib"
	"golang.org/x/pkgsite/internal/version"
)

const (
	// LatestVersion signifies the latest available version in requests to the
	// proxy client.
	LatestVersion = "latest"

	// MasterVersion signifies the version at master.
	MasterVersion = "master"

	// UnknownModulePath signifies that the module path for a given package
	// path is ambiguous or not known. This is because requests to the
	// frontend can come in the form of <import-path>[@<version>], and it is
	// not clear which part of the import-path is the module path.
	UnknownModulePath = "unknownModulePath"
)

// ModuleInfo holds metadata associated with a module.
type ModuleInfo struct {
	ModulePath        string
	Version           string
	CommitTime        time.Time
	VersionType       version.Type
	IsRedistributable bool
	HasGoMod          bool // whether the module zip has a go.mod file
	SourceInfo        *source.Info
}

// LegacyModuleInfo holds metadata associated with a module.
type LegacyModuleInfo struct {
	ModuleInfo
	LegacyReadmeFilePath string
	LegacyReadmeContents string
}

// VersionMap holds metadata associated with module queries for a version.
type VersionMap struct {
	ModulePath       string
	RequestedVersion string
	ResolvedVersion  string
	GoModPath        string
	Status           int
	Error            string
	UpdatedAt        time.Time
}

// SeriesPath returns the series path for the module.
//
// A series is a group of modules that share the same base path and are assumed
// to be major-version variants.
//
// The series path is the module path without the version. For most modules,
// this will be the module path for all module versions with major version 0 or
// 1. For gopkg.in modules, the series path does not correspond to any module
// version.
//
// Examples:
// The module paths "a/b" and "a/b/v2"  both have series path "a/b".
// The module paths "gopkg.in/yaml.v1" and "gopkg.in/yaml.v2" both have series
// path "gopkg.in/yaml".
func (v *ModuleInfo) SeriesPath() string {
	return SeriesPathForModule(v.ModulePath)
}

// SeriesPathForModule returns the series path for the provided modulePath.
func SeriesPathForModule(modulePath string) string {
	seriesPath, _, _ := module.SplitPathVersion(modulePath)
	return seriesPath
}

// Suffix returns the suffix of the fullPath. It assumes that basePath is a
// prefix of fullPath. If fullPath and basePath are the same, the empty string
// is returned.
func Suffix(fullPath, basePath string) string {
	return strings.TrimPrefix(strings.TrimPrefix(fullPath, basePath), "/")
}

// V1Path returns the path for version 1 of the package whose path
// is modulePath + "/" + suffix. If modulePath is the standard
// library, then V1Path returns suffix.
func V1Path(modulePath, suffix string) string {
	if modulePath == stdlib.ModulePath {
		return suffix
	}
	return path.Join(SeriesPathForModule(modulePath), suffix)
}

// A Module is a specific, reproducible build of a module.
type Module struct {
	LegacyModuleInfo
	// Licenses holds all licenses within this module version, including those
	// that may be contained in nested subdirectories.
	Licenses    []*licenses.License
	Directories []*Directory

	LegacyPackages []*LegacyPackage
}

// VersionedDirectory is a Directory along with its corresponding module
// information.
type VersionedDirectory struct {
	Directory
	ModuleInfo
}

// DirectoryMeta represents the metadata of a directory in a module version.
type DirectoryMeta struct {
	Path              string
	V1Path            string
	IsRedistributable bool
	Licenses          []*licenses.Metadata // metadata of applicable licenses
}

// Directory represents a directory in a module version, and the contents of that directory.
// It will replace LegacyDirectory once everything has been migrated.
type Directory struct {
	DirectoryMeta
	Readme  *Readme
	Package *Package
}

// PackageMeta represents the metadata of a package in a module version.
type PackageMeta struct {
	DirectoryMeta
	Name     string
	Synopsis string
}

// PackageMetaFromLegacyPackage returns a PackageMeta based on data from a
// LegacyPackage.
func PackageMetaFromLegacyPackage(pkg *LegacyPackage) *PackageMeta {
	return &PackageMeta{
		DirectoryMeta: DirectoryMeta{
			Path:              pkg.Path,
			V1Path:            pkg.V1Path,
			Licenses:          pkg.Licenses,
			IsRedistributable: pkg.IsRedistributable,
		},
		Name:     pkg.Name,
		Synopsis: pkg.Synopsis,
	}
}

// Package is a group of one or more Go source files with the same package
// header. A Package is part of a directory.
// It will replace LegacyPackage once everything has been migrated.
type Package struct {
	Name          string
	Path          string
	Documentation *Documentation
	Imports       []string
}

// Documentation is the rendered documentation for a given package
// for a specific GOOS and GOARCH.
type Documentation struct {
	// The values of the GOOS and GOARCH environment variables used to parse the
	// package.
	GOOS     string
	GOARCH   string
	Synopsis string
	HTML     safehtml.HTML
}

// Readme is a README at a given directory.
type Readme struct {
	Filepath string
	Contents string
}

// IndexVersion holds the version information returned by the module index.
type IndexVersion struct {
	Path      string
	Version   string
	Timestamp time.Time
}

// ModuleVersionState holds a worker module version state.
type ModuleVersionState struct {
	ModulePath string
	Version    string

	// IndexTimestamp is the timestamp received from the Index for this version,
	// which should correspond to the time this version was committed to the
	// Index.
	IndexTimestamp time.Time
	// CreatedAt is the time this version was originally inserted into the
	// module version state table.
	CreatedAt time.Time

	// Status is the most recent HTTP status code received from the Fetch service
	// for this version, or nil if no request to the fetch service has been made.
	Status int
	// Error is the most recent HTTP response body received from the Fetch
	// service, for a response with an unsuccessful status code. It is used for
	// debugging only, and has no semantic significance.
	Error string
	// TryCount is the number of times a fetch of this version has been
	// attempted.
	TryCount int
	// LastProcessedAt is the last time this version was updated with a result
	// from the fetch service.
	LastProcessedAt *time.Time
	// NextProcessedAfter is the next time a fetch for this version should be
	// attempted.
	NextProcessedAfter time.Time

	// AppVersion is the value of the GAE_VERSION environment variable, which is
	// set by app engine. It is a timestamp in the format 20190709t112655 that
	// is close to, but not the same as, the deployment time. For example, the
	// deployment time for the above timestamp might be Jul 9, 2019, 11:29:59 AM.
	AppVersion string

	// GoModPath is the path declared in the go.mod file.
	GoModPath string

	// NumPackages it the number of packages that were processed as part of the
	// module (regardless of whether the processing was successful).
	NumPackages *int
}

// PackageVersionState holds a worker package version state. It is associated
// with a given module version state.
type PackageVersionState struct {
	PackagePath string
	ModulePath  string
	Version     string
	Status      int
	Error       string
}

// SearchResult represents a single search result from SearchDocuments.
type SearchResult struct {
	Name        string
	PackagePath string
	ModulePath  string
	Version     string
	Synopsis    string
	Licenses    []string

	CommitTime time.Time
	// Score is used to sort items in an array of SearchResult.
	Score float64

	// NumImportedBy is the number of packages that import PackagePath.
	NumImportedBy uint64

	// NumResults is the total number of packages that were returned for this
	// search.
	NumResults uint64
	// Approximate reports whether NumResults is an approximate count. NumResults
	// can be approximate if search scanned only a subset of documents, and
	// result count is estimated using the hyperloglog algorithm.
	Approximate bool
}

// A FieldSet is a bit set of struct fields. It is used to avoid reading large
// struct fields from the data store. FieldSet is also the type of the
// individual bit values. (Think of them as singleton sets.)
//
// NoFields (the zero value) is the empty set. AllFields is the set containing
// every field.
//
// FieldSet bits are unique across the entire project, because some types are
// concatenations (via embedding) of others. For example, a
// LegacyVersionedPackage contains the fields of both a LegacyModuleInfo and a
// LegacyPackage, so we can't use the
// same bits for both LegacyModuleInfo's LegacyReadmeContents field and
// LegacyPackage's DocumentationHTML field.
type FieldSet int64

// MinimalFields is the empty FieldSet.
const MinimalFields FieldSet = 0

// AllFields is the FieldSet that contains all fields.
const AllFields FieldSet = -1

// StringFieldMissing is the value for string fields that are not present
// in a struct. We use it to distinguish a (possibly valid) empty string
// from a field that was never populated.
const StringFieldMissing = "!MISSING"

// FieldSet bits for fields that can be conditionally read from the data store.
const (
	WithReadmeContents FieldSet = 1 << iota
	WithDocumentationHTML
)

// LegacyDirectory represents a directory in a module version, and all of the
// packages inside that directory.
type LegacyDirectory struct {
	LegacyModuleInfo
	Path     string
	Packages []*LegacyPackage
}

// A LegacyPackage is a group of one or more Go source files with the same
// package header. LegacyPackages are part of a module.
type LegacyPackage struct {
	Path              string
	Name              string
	Synopsis          string
	IsRedistributable bool
	Licenses          []*licenses.Metadata // metadata of applicable licenses
	Imports           []string
	DocumentationHTML safehtml.HTML
	// The values of the GOOS and GOARCH environment variables used to parse the
	// package.
	GOOS   string
	GOARCH string

	// V1Path is the package path of a package with major version 1 in a given
	// series.
	V1Path string
}

// LegacyVersionedPackage is a LegacyPackage along with its corresponding module
// information.
type LegacyVersionedPackage struct {
	LegacyPackage
	LegacyModuleInfo
}