// Copyright 2019 The Hugo Authors. All rights reserved.
//
// 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 hugolib

import (
	"context"
	"fmt"
	"os"
	pth "path"
	"path/filepath"
	"strings"

	"github.com/gohugoio/hugo/config"

	"github.com/gohugoio/hugo/hugofs/files"

	"github.com/gohugoio/hugo/resources"

	"github.com/pkg/errors"
	"golang.org/x/sync/errgroup"

	"github.com/gohugoio/hugo/common/hugio"

	"github.com/gohugoio/hugo/resources/resource"

	"github.com/gohugoio/hugo/source"

	"github.com/gohugoio/hugo/hugofs"

	"github.com/gohugoio/hugo/common/loggers"
	"github.com/spf13/afero"
)

func newPagesCollector(
	sp *source.SourceSpec,
	logger *loggers.Logger,
	contentTracker *contentChangeMap,
	proc pagesCollectorProcessorProvider, filenames ...string) *pagesCollector {

	return &pagesCollector{
		fs:        sp.SourceFs,
		proc:      proc,
		sp:        sp,
		logger:    logger,
		filenames: filenames,
		tracker:   contentTracker,
	}
}

func newPagesProcessor(h *HugoSites, sp *source.SourceSpec, partialBuild bool) *pagesProcessor {

	return &pagesProcessor{
		h:            h,
		sp:           sp,
		partialBuild: partialBuild,
		numWorkers:   config.GetNumWorkerMultiplier() * 3,
	}
}

type fileinfoBundle struct {
	header    hugofs.FileMetaInfo
	resources []hugofs.FileMetaInfo
}

func (b *fileinfoBundle) containsResource(name string) bool {
	for _, r := range b.resources {
		if r.Name() == name {
			return true
		}
	}

	return false

}

type pageBundles map[string]*fileinfoBundle

type pagesCollector struct {
	sp     *source.SourceSpec
	fs     afero.Fs
	logger *loggers.Logger

	// Ordered list (bundle headers first) used in partial builds.
	filenames []string

	// Content files tracker used in partial builds.
	tracker *contentChangeMap

	proc pagesCollectorProcessorProvider
}

type contentDirKey struct {
	dirname  string
	filename string
	tp       bundleDirType
}

// Collect.
func (c *pagesCollector) Collect() error {
	c.proc.Start(context.Background())
	if c.tracker != nil {
		c.tracker.start()
		defer c.tracker.stop()
	}

	var collectErr error
	if len(c.filenames) == 0 {
		// Collect everything.
		collectErr = c.collectDir("", false, nil)
	} else {
		dirs := make(map[contentDirKey]bool)
		for _, filename := range c.filenames {
			dir, filename, btype := c.tracker.resolveAndRemove(filename)
			dirs[contentDirKey{dir, filename, btype}] = true
		}

		for dir, _ := range dirs {
			switch dir.tp {
			case bundleLeaf, bundleBranch:
				collectErr = c.collectDir(dir.dirname, true, nil)
			default:
				// We always start from a directory.
				collectErr = c.collectDir(dir.dirname, true, func(fim hugofs.FileMetaInfo) bool {
					return strings.HasSuffix(dir.filename, fim.Meta().Path())
				})
			}

			if collectErr != nil {
				break
			}
		}

	}

	err := c.proc.Wait()

	if collectErr != nil {
		return collectErr
	}

	return err
}

func (c *pagesCollector) collectDir(dirname string, partial bool, inFilter func(fim hugofs.FileMetaInfo) bool) error {
	fi, err := c.fs.Stat(dirname)
	if err != nil {
		if os.IsNotExist(err) {
			// May have been deleted.
			return nil
		}
		return err
	}

	handleDir := func(
		btype bundleDirType,
		dir hugofs.FileMetaInfo,
		path string,
		readdir []hugofs.FileMetaInfo) error {

		if btype > bundleNot && c.tracker != nil {
			c.tracker.add(path, btype)
		}

		if btype == bundleBranch {
			if err := c.handleBundleBranch(readdir); err != nil {
				return err
			}
			// A branch bundle is only this directory level, so keep walking.
			return nil
		} else if btype == bundleLeaf {
			if err := c.handleBundleLeaf(dir, path, readdir); err != nil {
				return err
			}

			return nil
		}

		if err := c.handleFiles(readdir...); err != nil {
			return err
		}

		return nil

	}

	filter := func(fim hugofs.FileMetaInfo) bool {
		if fim.Meta().SkipDir() {
			return false
		}

		if c.sp.IgnoreFile(fim.Meta().Filename()) {
			return false
		}

		if inFilter != nil {
			return inFilter(fim)
		}
		return true
	}

	preHook := func(dir hugofs.FileMetaInfo, path string, readdir []hugofs.FileMetaInfo) ([]hugofs.FileMetaInfo, error) {
		var btype bundleDirType

		filtered := readdir[:0]
		for _, fi := range readdir {
			if filter(fi) {
				filtered = append(filtered, fi)
				if c.tracker != nil {
					// Track symlinks.
					c.tracker.addSymbolicLinkMapping(fi)
				}
			}
		}
		readdir = filtered

		// We merge language directories, so there can be duplicates, but they
		// will be ordered, most important first.
		var duplicates []int
		seen := make(map[string]bool)

		for i, fi := range readdir {

			if fi.IsDir() {
				continue
			}

			meta := fi.Meta()
			class := meta.Classifier()
			translationBase := meta.TranslationBaseNameWithExt()
			key := pth.Join(meta.Lang(), translationBase)

			if seen[key] {
				duplicates = append(duplicates, i)
				continue
			}
			seen[key] = true

			var thisBtype bundleDirType

			switch class {
			case files.ContentClassLeaf:
				thisBtype = bundleLeaf
			case files.ContentClassBranch:
				thisBtype = bundleBranch
			}

			// Folders with both index.md and _index.md type of files have
			// undefined behaviour and can never work.
			// The branch variant will win because of sort order, but log
			// a warning about it.
			if thisBtype > bundleNot && btype > bundleNot && thisBtype != btype {
				c.logger.WARN.Printf("Content directory %q have both index.* and _index.* files, pick one.", dir.Meta().Filename())
				// Reclassify it so it will be handled as a content file inside the
				// section, which is in line with the <= 0.55 behaviour.
				meta["classifier"] = files.ContentClassContent
			} else if thisBtype > bundleNot {
				btype = thisBtype
			}

		}

		if len(duplicates) > 0 {
			for i := len(duplicates) - 1; i >= 0; i-- {
				idx := duplicates[i]
				readdir = append(readdir[:idx], readdir[idx+1:]...)
			}
		}

		err := handleDir(btype, dir, path, readdir)
		if err != nil {
			return nil, err
		}

		if btype == bundleLeaf || partial {
			return nil, filepath.SkipDir
		}

		// Keep walking.
		return readdir, nil

	}

	var postHook hugofs.WalkHook
	if c.tracker != nil {
		postHook = func(dir hugofs.FileMetaInfo, path string, readdir []hugofs.FileMetaInfo) ([]hugofs.FileMetaInfo, error) {
			if c.tracker == nil {
				// Nothing to do.
				return readdir, nil
			}

			return readdir, nil
		}
	}

	wfn := func(path string, info hugofs.FileMetaInfo, err error) error {
		if err != nil {
			return err
		}

		return nil
	}

	w := hugofs.NewWalkway(hugofs.WalkwayConfig{
		Fs:       c.fs,
		Logger:   c.logger,
		Root:     dirname,
		Info:     fi.(hugofs.FileMetaInfo),
		HookPre:  preHook,
		HookPost: postHook,
		WalkFn:   wfn})

	return w.Walk()

}

func (c *pagesCollector) isBundleHeader(fi hugofs.FileMetaInfo) bool {
	class := fi.Meta().Classifier()
	return class == files.ContentClassLeaf || class == files.ContentClassBranch
}

func (c *pagesCollector) getLang(fi hugofs.FileMetaInfo) string {
	lang := fi.Meta().Lang()
	if lang != "" {
		return lang
	}

	return c.sp.DefaultContentLanguage
}

func (c *pagesCollector) addToBundle(info hugofs.FileMetaInfo, btyp bundleDirType, bundles pageBundles) error {
	getBundle := func(lang string) *fileinfoBundle {
		return bundles[lang]
	}

	cloneBundle := func(lang string) *fileinfoBundle {
		// Every bundled content file needs a content file header.
		// Use the default content language if found, else just
		// pick one.
		var (
			source *fileinfoBundle
			found  bool
		)

		source, found = bundles[c.sp.DefaultContentLanguage]
		if !found {
			for _, b := range bundles {
				source = b
				break
			}
		}

		if source == nil {
			panic(fmt.Sprintf("no source found, %d", len(bundles)))
		}

		clone := c.cloneFileInfo(source.header)
		clone.Meta()["lang"] = lang

		return &fileinfoBundle{
			header: clone,
		}
	}

	lang := c.getLang(info)
	bundle := getBundle(lang)
	isBundleHeader := c.isBundleHeader(info)
	classifier := info.Meta().Classifier()
	isContent := classifier == files.ContentClassContent
	if bundle == nil {
		if isBundleHeader {
			bundle = &fileinfoBundle{header: info}
			bundles[lang] = bundle
		} else {
			if btyp == bundleBranch {
				// No special logic for branch bundles.
				// Every language needs its own _index.md file.
				// Also, we only clone bundle headers for lonsesome, bundled,
				// content files.
				return c.handleFiles(info)
			}

			if isContent {
				bundle = cloneBundle(lang)
				bundles[lang] = bundle
			}
		}
	}

	if !isBundleHeader && bundle != nil {
		bundle.resources = append(bundle.resources, info)
	}

	if classifier == files.ContentClassFile {
		translations := info.Meta().Translations()

		for lang, b := range bundles {
			if !stringSliceContains(lang, translations...) && !b.containsResource(info.Name()) {

				// Clone and add it to the bundle.
				clone := c.cloneFileInfo(info)
				clone.Meta()["lang"] = lang
				b.resources = append(b.resources, clone)
			}
		}
	}

	return nil
}

func (c *pagesCollector) cloneFileInfo(fi hugofs.FileMetaInfo) hugofs.FileMetaInfo {
	cm := hugofs.FileMeta{}
	meta := fi.Meta()
	if meta == nil {
		panic(fmt.Sprintf("not meta: %v", fi.Name()))
	}
	for k, v := range meta {
		cm[k] = v
	}

	return hugofs.NewFileMetaInfo(fi, cm)
}

func (c *pagesCollector) handleBundleBranch(readdir []hugofs.FileMetaInfo) error {

	// Maps bundles to its language.
	bundles := pageBundles{}

	for _, fim := range readdir {

		if fim.IsDir() {
			continue
		}

		meta := fim.Meta()

		switch meta.Classifier() {
		case files.ContentClassContent:
			if err := c.handleFiles(fim); err != nil {
				return err
			}
		default:
			if err := c.addToBundle(fim, bundleBranch, bundles); err != nil {
				return err
			}
		}

	}

	return c.proc.Process(bundles)

}

func (c *pagesCollector) handleBundleLeaf(dir hugofs.FileMetaInfo, path string, readdir []hugofs.FileMetaInfo) error {
	// Maps bundles to its language.
	bundles := pageBundles{}

	walk := func(path string, info hugofs.FileMetaInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() {
			return nil
		}

		return c.addToBundle(info, bundleLeaf, bundles)

	}

	// Start a new walker from the given path.
	w := hugofs.NewWalkway(hugofs.WalkwayConfig{
		Root:       path,
		Fs:         c.fs,
		Logger:     c.logger,
		Info:       dir,
		DirEntries: readdir,
		WalkFn:     walk})

	if err := w.Walk(); err != nil {
		return err
	}

	return c.proc.Process(bundles)

}

func (c *pagesCollector) handleFiles(fis ...hugofs.FileMetaInfo) error {
	for _, fi := range fis {
		if fi.IsDir() {
			continue
		}

		if err := c.proc.Process(fi); err != nil {
			return err
		}
	}
	return nil
}

type pagesCollectorProcessorProvider interface {
	Process(item interface{}) error
	Start(ctx context.Context) context.Context
	Wait() error
}

type pagesProcessor struct {
	h  *HugoSites
	sp *source.SourceSpec

	itemChan  chan interface{}
	itemGroup *errgroup.Group

	// The output Pages
	pagesChan  chan *pageState
	pagesGroup *errgroup.Group

	numWorkers int

	partialBuild bool
}

func (proc *pagesProcessor) Process(item interface{}) error {
	proc.itemChan <- item
	return nil
}

func (proc *pagesProcessor) Start(ctx context.Context) context.Context {
	proc.pagesChan = make(chan *pageState, proc.numWorkers)
	proc.pagesGroup, ctx = errgroup.WithContext(ctx)
	proc.itemChan = make(chan interface{}, proc.numWorkers)
	proc.itemGroup, ctx = errgroup.WithContext(ctx)

	proc.pagesGroup.Go(func() error {
		for p := range proc.pagesChan {
			s := p.s
			p.forceRender = proc.partialBuild

			if p.forceRender {
				s.replacePage(p)
			} else {
				s.addPage(p)
			}
		}
		return nil
	})

	for i := 0; i < proc.numWorkers; i++ {
		proc.itemGroup.Go(func() error {
			for item := range proc.itemChan {
				select {
				case <-proc.h.Done():
					return nil
				default:
					if err := proc.process(item); err != nil {
						proc.h.SendError(err)
					}
				}
			}

			return nil
		})
	}

	return ctx
}

func (proc *pagesProcessor) Wait() error {
	close(proc.itemChan)

	err := proc.itemGroup.Wait()

	close(proc.pagesChan)

	if err != nil {
		return err
	}

	return proc.pagesGroup.Wait()
}

func (proc *pagesProcessor) newPageFromBundle(b *fileinfoBundle) (*pageState, error) {
	p, err := proc.newPageFromFi(b.header, nil)
	if err != nil {
		return nil, err
	}

	if len(b.resources) > 0 {

		resources := make(resource.Resources, len(b.resources))

		for i, rfi := range b.resources {
			meta := rfi.Meta()
			classifier := meta.Classifier()
			var r resource.Resource
			switch classifier {
			case files.ContentClassContent:
				rp, err := proc.newPageFromFi(rfi, p)
				if err != nil {
					return nil, err
				}
				rp.m.resourcePath = filepath.ToSlash(strings.TrimPrefix(rp.Path(), p.File().Dir()))

				r = rp

			case files.ContentClassFile:
				r, err = proc.newResource(rfi, p)
				if err != nil {
					return nil, err
				}
			default:
				panic(fmt.Sprintf("invalid classifier: %q", classifier))
			}

			resources[i] = r

		}

		p.addResources(resources...)
	}

	return p, nil
}

func (proc *pagesProcessor) newPageFromFi(fim hugofs.FileMetaInfo, owner *pageState) (*pageState, error) {
	fi, err := newFileInfo(proc.sp, fim)
	if err != nil {
		return nil, err
	}

	var s *Site
	meta := fim.Meta()

	if owner != nil {
		s = owner.s
	} else {
		lang := meta.Lang()
		s = proc.getSite(lang)
	}

	r := func() (hugio.ReadSeekCloser, error) {
		return meta.Open()
	}

	p, err := newPageWithContent(fi, s, owner != nil, r)
	if err != nil {
		return nil, err
	}
	p.parent = owner
	return p, nil
}

func (proc *pagesProcessor) newResource(fim hugofs.FileMetaInfo, owner *pageState) (resource.Resource, error) {

	// TODO(bep) consolidate with multihost logic + clean up
	outputFormats := owner.m.outputFormats()
	seen := make(map[string]bool)
	var targetBasePaths []string
	// Make sure bundled resources are published to all of the ouptput formats'
	// sub paths.
	for _, f := range outputFormats {
		p := f.Path
		if seen[p] {
			continue
		}
		seen[p] = true
		targetBasePaths = append(targetBasePaths, p)

	}

	meta := fim.Meta()
	r := func() (hugio.ReadSeekCloser, error) {
		return meta.Open()
	}

	target := strings.TrimPrefix(meta.Path(), owner.File().Dir())

	return owner.s.ResourceSpec.New(
		resources.ResourceSourceDescriptor{
			TargetPaths:        owner.getTargetPaths,
			OpenReadSeekCloser: r,
			FileInfo:           fim,
			RelTargetFilename:  target,
			TargetBasePaths:    targetBasePaths,
		})
}

func (proc *pagesProcessor) getSite(lang string) *Site {
	if lang == "" {
		return proc.h.Sites[0]
	}

	for _, s := range proc.h.Sites {
		if lang == s.Lang() {
			return s
		}
	}
	return proc.h.Sites[0]
}

func (proc *pagesProcessor) copyFile(fim hugofs.FileMetaInfo) error {
	meta := fim.Meta()
	s := proc.getSite(meta.Lang())
	f, err := meta.Open()
	if err != nil {
		return errors.Wrap(err, "copyFile: failed to open")
	}

	target := filepath.Join(s.PathSpec.GetTargetLanguageBasePath(), meta.Path())

	defer f.Close()

	return s.publish(&s.PathSpec.ProcessingStats.Files, target, f)

}

func (proc *pagesProcessor) process(item interface{}) error {
	send := func(p *pageState, err error) {
		if err != nil {
			proc.sendError(err)
		} else {
			proc.pagesChan <- p
		}
	}

	switch v := item.(type) {
	// Page bundles mapped to their language.
	case pageBundles:
		for _, bundle := range v {
			if proc.shouldSkip(bundle.header) {
				continue
			}
			send(proc.newPageFromBundle(bundle))
		}
	case hugofs.FileMetaInfo:
		if proc.shouldSkip(v) {
			return nil
		}
		meta := v.Meta()

		classifier := meta.Classifier()
		switch classifier {
		case files.ContentClassContent:
			send(proc.newPageFromFi(v, nil))
		case files.ContentClassFile:
			proc.sendError(proc.copyFile(v))
		default:
			panic(fmt.Sprintf("invalid classifier: %q", classifier))
		}
	default:
		panic(fmt.Sprintf("unrecognized item type in Process: %T", item))
	}

	return nil
}

func (proc *pagesProcessor) sendError(err error) {
	if err == nil {
		return
	}
	proc.h.SendError(err)
}

func (proc *pagesProcessor) shouldSkip(fim hugofs.FileMetaInfo) bool {
	return proc.sp.DisabledLanguages[fim.Meta().Lang()]
}

func stringSliceContains(k string, values ...string) bool {
	for _, v := range values {
		if k == v {
			return true
		}
	}
	return false
}