package frontend

import (
	"context"
	"errors"

	"github.com/google/safehtml"
	"github.com/google/safehtml/template"
	"golang.org/x/mod/semver"
	"golang.org/x/pkgsite/internal"
	"golang.org/x/pkgsite/internal/derrors"
	"golang.org/x/pkgsite/internal/godoc"
	"golang.org/x/pkgsite/internal/godoc/dochtml"
	"golang.org/x/pkgsite/internal/log"
	"golang.org/x/pkgsite/internal/middleware"
	"golang.org/x/pkgsite/internal/version"
)

	Directories *Directories

	Licenses []LicenseMetadata

	NumImports int

	CommitTime string

	Readme safehtml.HTML

	ReadmeOutline []*Heading

	ReadmeLinks []link

	DocLinks []link

	ModuleReadmeLinks []link

	ImportedByCount int

	DocBody       safehtml.HTML
	DocOutline    safehtml.HTML
	MobileOutline safehtml.HTML
	IsPackage     bool

	DocSynopsis string

	GOOS, GOARCH string

	BuildContexts []internal.BuildContext

	SourceFiles []*File

	RepositoryURL string

	SourceURL string

	ExpandReadme bool

	ModFileURL string

	IsTaggedVersion bool

	IsStableVersion bool
}

type File struct {
	Name string
	URL  string
}

func fetchMainDetails(ctx context.Context, ds internal.DataSource, um *internal.UnitMeta, expandReadme bool, bc internal.BuildContext) (_ *MainDetails, err error) {
	defer middleware.ElapsedStat(ctx, "fetchMainDetails")()

	unit, err := ds.GetUnit(ctx, um, internal.WithMain, bc)
	if err != nil {
		return nil, err
	}
	subdirectories := getSubdirectories(um, unit.Subdirectories)
	if err != nil {
		return nil, err
	}
	nestedModules, err := getNestedModules(ctx, ds, um, subdirectories)
	if err != nil {
		return nil, err
	}
	readme, err := readmeContent(ctx, unit)
	if err != nil {
		return nil, err
	}
	var (
		docParts           = &dochtml.Parts{}
		docLinks, modLinks []link
		files              []*File
		synopsis           string
		goos, goarch       string
		buildContexts      []internal.BuildContext
	)

	var doc *internal.Documentation
	if len(unit.Documentation) > 0 {
		doc = unit.Documentation[0]
	}

	if doc != nil {
		synopsis = doc.Synopsis
		goos = doc.GOOS
		goarch = doc.GOARCH
		buildContexts = unit.BuildContexts
		end := middleware.ElapsedStat(ctx, "DecodePackage")
		docPkg, err := godoc.DecodePackage(doc.Source)
		end()
		if err != nil {

				log.Errorf(ctx, "fetchMainDetails(%q, %q, %q): %v", um.Path, um.ModulePath, um.Version, err)
				return nil, errUnitNotFoundWithoutFetch
			}
			return nil, err
		}

		if err != nil && !errors.Is(err, dochtml.ErrTooLarge) {
			return nil, err
		}
		for _, l := range docParts.Links {
			docLinks = append(docLinks, link{Href: l.Href, Body: l.Text})
		}
		end = middleware.ElapsedStat(ctx, "sourceFiles")
		files = sourceFiles(unit, docPkg)
		end()

	if unit.Path != unit.ModulePath && unit.IsRedistributable {
		modReadme, err := ds.GetModuleReadme(ctx, unit.ModulePath, unit.Version)
		if err != nil && !errors.Is(err, derrors.NotFound) {
			return nil, err
		}
		if err == nil {
			rm, err := processReadme(ctx, modReadme, um.SourceInfo)
			if err != nil {
				return nil, err
			}
			modLinks = rm.Links
		}
	}

	versionType, err := version.ParseType(um.Version)
	if err != nil {
		return nil, err
	}
	isTaggedVersion := versionType != version.TypePseudo
	isStableVersion := semver.Major(um.Version) != "v0" && versionType == version.TypeRelease
	return &MainDetails{
		ExpandReadme:      expandReadme,
		Directories:       unitDirectories(append(subdirectories, nestedModules...)),
		Licenses:          transformLicenseMetadata(um.Licenses),
		CommitTime:        absoluteTime(um.CommitTime),
		Readme:            readme.HTML,
		ReadmeOutline:     readme.Outline,
		ReadmeLinks:       readme.Links,
		DocLinks:          docLinks,
		ModuleReadmeLinks: modLinks,
		DocOutline:        docParts.Outline,
		DocBody:           docParts.Body,
		DocSynopsis:       synopsis,
		GOOS:              goos,
		GOARCH:            goarch,
		BuildContexts:     buildContexts,
		SourceFiles:       files,
		RepositoryURL:     um.SourceInfo.RepoURL(),
		SourceURL:         um.SourceInfo.DirectoryURL(internal.Suffix(um.Path, um.ModulePath)),
		MobileOutline:     docParts.MobileOutline,
		NumImports:        unit.NumImports,
		ImportedByCount:   unit.NumImportedBy,
		IsPackage:         unit.IsPackage(),
		ModFileURL:        um.SourceInfo.ModuleURL() + "/go.mod",
		IsTaggedVersion:   isTaggedVersion,
		IsStableVersion:   isStableVersion,
	}, nil
}

	if len(docs) > 1 && docs[0].BuildContext() == internal.BuildContextAll {
		return docs[:1]

	if len(docs) == 1 && docs[0].GOOS == "linux" && docs[0].GOARCH == "amd64" {
		docs[0].GOOS = internal.All
		docs[0].GOARCH = internal.All
	}
	return docs
}

func readmeContent(ctx context.Context, u *internal.Unit) (_ *Readme, err error) {
	defer derrors.Wrap(&err, "readmeContent(%q, %q, %q)", u.Path, u.ModulePath, u.Version)
	defer middleware.ElapsedStat(ctx, "readmeContent")()
	if !u.IsRedistributable {
		return &Readme{}, nil
	}
	return ProcessReadme(ctx, u)
}

const missingDocReplacement = `<p>Documentation is missing.</p>`

func getHTML(ctx context.Context, u *internal.Unit, docPkg *godoc.Package,
	nameToVersion map[string]string) (_ *dochtml.Parts, err error) {
	defer derrors.Wrap(&err, "getHTML(%s)", u.Path)

	if len(u.Documentation[0].Source) > 0 {
		return renderDocParts(ctx, u, docPkg, nameToVersion)
	}
	log.Errorf(ctx, "unit %s (%s@%s) missing documentation source", u.Path, u.ModulePath, u.Version)
	return &dochtml.Parts{Body: template.MustParseAndExecuteToHTML(missingDocReplacement)}, nil