// Copyright 2016 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 tplimpl

import (
	"html/template"
	"io"
	"os"
	"path/filepath"
	"strings"

	"sync"

	"github.com/eknkc/amber"
	"github.com/spf13/afero"
	bp "github.com/spf13/hugo/bufferpool"
	"github.com/spf13/hugo/deps"
	"github.com/spf13/hugo/helpers"
	"github.com/spf13/hugo/output"
	"github.com/yosssi/ace"
)

// TODO(bep) globals get rid of the rest of the jww.ERR etc.

// Protecting global map access (Amber)
var amberMu sync.Mutex

type templateErr struct {
	name string
	err  error
}

type GoHTMLTemplate struct {
	*template.Template

	// This looks, and is, strange.
	// The clone is used by non-renderable content pages, and these need to be
	// re-parsed on content change, and to avoid the
	// "cannot Parse after Execute" error, we need to re-clone it from the original clone.
	clone      *template.Template
	cloneClone *template.Template

	// a separate storage for the overlays created from cloned master templates.
	// note: No mutex protection, so we add these in one Go routine, then just read.
	overlays map[string]*template.Template

	errors []*templateErr

	funcster *templateFuncster

	amberFuncMap template.FuncMap

	*deps.Deps
}

type TemplateProvider struct{}

var DefaultTemplateProvider *TemplateProvider

// Update updates the Hugo Template System in the provided Deps.
// with all the additional features, templates & functions
func (*TemplateProvider) Update(deps *deps.Deps) error {
	tmpl := &GoHTMLTemplate{
		Template: template.New(""),
		overlays: make(map[string]*template.Template),
		errors:   make([]*templateErr, 0),
		Deps:     deps,
	}

	deps.Tmpl = tmpl

	tmpl.initFuncs(deps)

	tmpl.LoadEmbedded()

	if deps.WithTemplate != nil {
		err := deps.WithTemplate(tmpl)
		if err != nil {
			tmpl.errors = append(tmpl.errors, &templateErr{"init", err})
		}

	}

	tmpl.MarkReady()

	return nil

}

// Clone clones
func (*TemplateProvider) Clone(d *deps.Deps) error {

	t := d.Tmpl.(*GoHTMLTemplate)

	// 1. Clone the clone with new template funcs
	// 2. Clone any overlays with new template funcs

	tmpl := &GoHTMLTemplate{
		Template: template.Must(t.Template.Clone()),
		overlays: make(map[string]*template.Template),
		errors:   make([]*templateErr, 0),
		Deps:     d,
	}

	d.Tmpl = tmpl
	tmpl.initFuncs(d)

	for k, v := range t.overlays {
		vc := template.Must(v.Clone())
		// The extra lookup is a workaround, see
		// * https://github.com/golang/go/issues/16101
		// * https://github.com/spf13/hugo/issues/2549
		vc = vc.Lookup(vc.Name())
		vc.Funcs(tmpl.funcster.funcMap)
		tmpl.overlays[k] = vc
	}

	tmpl.MarkReady()

	return nil
}

func (t *GoHTMLTemplate) initFuncs(d *deps.Deps) {

	t.funcster = newTemplateFuncster(d)

	// The URL funcs in the funcMap is somewhat language dependent,
	// so we need to wait until the language and site config is loaded.
	t.funcster.initFuncMap()

	t.amberFuncMap = template.FuncMap{}

	amberMu.Lock()
	for k, v := range amber.FuncMap {
		t.amberFuncMap[k] = v
	}

	for k, v := range t.funcster.funcMap {
		t.amberFuncMap[k] = v
		// Hacky, but we need to make sure that the func names are in the global map.
		amber.FuncMap[k] = func() string {
			panic("should never be invoked")
		}
	}
	amberMu.Unlock()

}

func (t *GoHTMLTemplate) Funcs(funcMap template.FuncMap) {
	t.Template.Funcs(funcMap)
}

func (t *GoHTMLTemplate) Partial(name string, contextList ...interface{}) template.HTML {
	if strings.HasPrefix("partials/", name) {
		name = name[8:]
	}
	var context interface{}

	if len(contextList) == 0 {
		context = nil
	} else {
		context = contextList[0]
	}
	return t.ExecuteTemplateToHTML(context, "partials/"+name, "theme/partials/"+name)
}

func (t *GoHTMLTemplate) executeTemplate(context interface{}, w io.Writer, layouts ...string) {
	var worked bool
	for _, layout := range layouts {
		templ := t.Lookup(layout)
		if templ == nil {
			// TODO(bep) output
			layout += ".html"
			templ = t.Lookup(layout)
		}

		if templ != nil {
			if err := templ.Execute(w, context); err != nil {
				helpers.DistinctErrorLog.Println(layout, err)
			}
			worked = true
			break
		}
	}
	if !worked {
		t.Log.ERROR.Println("Unable to render", layouts)
		t.Log.ERROR.Println("Expecting to find a template in either the theme/layouts or /layouts in one of the following relative locations", layouts)
	}
}

func (t *GoHTMLTemplate) ExecuteTemplateToHTML(context interface{}, layouts ...string) template.HTML {
	b := bp.GetBuffer()
	defer bp.PutBuffer(b)
	t.executeTemplate(context, b, layouts...)
	return template.HTML(b.String())
}

func (t *GoHTMLTemplate) Lookup(name string) *template.Template {

	if templ := t.Template.Lookup(name); templ != nil {
		return templ
	}

	if t.overlays != nil {
		if templ, ok := t.overlays[name]; ok {
			return templ
		}
	}

	// The clone is used for the non-renderable HTML pages (p.IsRenderable == false) that is parsed
	// as Go templates late in the build process.
	if t.clone != nil {
		if templ := t.clone.Lookup(name); templ != nil {
			return templ
		}
	}

	return nil

}

func (t *GoHTMLTemplate) GetClone() *template.Template {
	return t.clone
}

func (t *GoHTMLTemplate) RebuildClone() *template.Template {
	t.clone = template.Must(t.cloneClone.Clone())
	return t.clone
}

func (t *GoHTMLTemplate) LoadEmbedded() {
	t.EmbedShortcodes()
	t.EmbedTemplates()
}

// MarkReady marks the template as "ready for execution". No changes allowed
// after this is set.
// TODO(bep) if this proves to be resource heavy, we could detect
// earlier if we really need this, or make it lazy.
func (t *GoHTMLTemplate) MarkReady() {
	if t.clone == nil {
		t.clone = template.Must(t.Template.Clone())
		t.cloneClone = template.Must(t.clone.Clone())
	}
}

func (t *GoHTMLTemplate) checkState() {
	if t.clone != nil {
		panic("template is cloned and cannot be modfified")
	}
}

func (t *GoHTMLTemplate) AddInternalTemplate(prefix, name, tpl string) error {
	if prefix != "" {
		return t.AddTemplate("_internal/"+prefix+"/"+name, tpl)
	}
	return t.AddTemplate("_internal/"+name, tpl)
}

func (t *GoHTMLTemplate) AddInternalShortcode(name, content string) error {
	return t.AddInternalTemplate("shortcodes", name, content)
}

func (t *GoHTMLTemplate) AddTemplate(name, tpl string) error {
	t.checkState()
	templ, err := t.New(name).Parse(tpl)
	if err != nil {
		t.errors = append(t.errors, &templateErr{name: name, err: err})
		return err
	}
	if err := applyTemplateTransformers(templ); err != nil {
		return err
	}

	return nil
}

func (t *GoHTMLTemplate) AddTemplateFileWithMaster(name, overlayFilename, masterFilename string) error {

	// There is currently no known way to associate a cloned template with an existing one.
	// This funky master/overlay design will hopefully improve in a future version of Go.
	//
	// Simplicity is hard.
	//
	// Until then we'll have to live with this hackery.
	//
	// See https://github.com/golang/go/issues/14285
	//
	// So, to do minimum amount of changes to get this to work:
	//
	// 1. Lookup or Parse the master
	// 2. Parse and store the overlay in a separate map

	masterTpl := t.Lookup(masterFilename)

	if masterTpl == nil {
		b, err := afero.ReadFile(t.Fs.Source, masterFilename)
		if err != nil {
			return err
		}
		masterTpl, err = t.New(masterFilename).Parse(string(b))

		if err != nil {
			// TODO(bep) Add a method that does this
			t.errors = append(t.errors, &templateErr{name: name, err: err})
			return err
		}
	}

	b, err := afero.ReadFile(t.Fs.Source, overlayFilename)
	if err != nil {
		return err
	}

	overlayTpl, err := template.Must(masterTpl.Clone()).Parse(string(b))
	if err != nil {
		t.errors = append(t.errors, &templateErr{name: name, err: err})
	} else {
		// The extra lookup is a workaround, see
		// * https://github.com/golang/go/issues/16101
		// * https://github.com/spf13/hugo/issues/2549
		overlayTpl = overlayTpl.Lookup(overlayTpl.Name())
		if err := applyTemplateTransformers(overlayTpl); err != nil {
			return err
		}
		t.overlays[name] = overlayTpl
	}

	return err
}

func (t *GoHTMLTemplate) AddAceTemplate(name, basePath, innerPath string, baseContent, innerContent []byte) error {
	t.checkState()
	var base, inner *ace.File
	name = name[:len(name)-len(filepath.Ext(innerPath))] + ".html"

	// Fixes issue #1178
	basePath = strings.Replace(basePath, "\\", "/", -1)
	innerPath = strings.Replace(innerPath, "\\", "/", -1)

	if basePath != "" {
		base = ace.NewFile(basePath, baseContent)
		inner = ace.NewFile(innerPath, innerContent)
	} else {
		base = ace.NewFile(innerPath, innerContent)
		inner = ace.NewFile("", []byte{})
	}
	parsed, err := ace.ParseSource(ace.NewSource(base, inner, []*ace.File{}), nil)
	if err != nil {
		t.errors = append(t.errors, &templateErr{name: name, err: err})
		return err
	}
	templ, err := ace.CompileResultWithTemplate(t.New(name), parsed, nil)
	if err != nil {
		t.errors = append(t.errors, &templateErr{name: name, err: err})
		return err
	}
	return applyTemplateTransformers(templ)
}

func (t *GoHTMLTemplate) AddTemplateFile(name, baseTemplatePath, path string) error {
	t.checkState()
	// get the suffix and switch on that
	ext := filepath.Ext(path)
	switch ext {
	case ".amber":
		templateName := strings.TrimSuffix(name, filepath.Ext(name)) + ".html"
		b, err := afero.ReadFile(t.Fs.Source, path)

		if err != nil {
			return err
		}

		amberMu.Lock()
		templ, err := t.CompileAmberWithTemplate(b, path, t.New(templateName))
		amberMu.Unlock()
		if err != nil {
			return err
		}

		return applyTemplateTransformers(templ)
	case ".ace":
		var innerContent, baseContent []byte
		innerContent, err := afero.ReadFile(t.Fs.Source, path)

		if err != nil {
			return err
		}

		if baseTemplatePath != "" {
			baseContent, err = afero.ReadFile(t.Fs.Source, baseTemplatePath)
			if err != nil {
				return err
			}
		}

		return t.AddAceTemplate(name, baseTemplatePath, path, baseContent, innerContent)
	default:

		if baseTemplatePath != "" {
			return t.AddTemplateFileWithMaster(name, path, baseTemplatePath)
		}

		b, err := afero.ReadFile(t.Fs.Source, path)

		if err != nil {
			return err
		}

		t.Log.DEBUG.Printf("Add template file from path %s", path)

		return t.AddTemplate(name, string(b))
	}

}

func (t *GoHTMLTemplate) GenerateTemplateNameFrom(base, path string) string {
	name, _ := filepath.Rel(base, path)
	return filepath.ToSlash(name)
}

func isDotFile(path string) bool {
	return filepath.Base(path)[0] == '.'
}

func isBackupFile(path string) bool {
	return path[len(path)-1] == '~'
}

const baseFileBase = "baseof"

func isBaseTemplate(path string) bool {
	return strings.Contains(path, baseFileBase)
}

func (t *GoHTMLTemplate) loadTemplates(absPath string, prefix string) {
	t.Log.DEBUG.Printf("Load templates from path %q prefix %q", absPath, prefix)
	walker := func(path string, fi os.FileInfo, err error) error {
		if err != nil {
			return nil
		}

		t.Log.DEBUG.Println("Template path", path)
		if fi.Mode()&os.ModeSymlink == os.ModeSymlink {
			link, err := filepath.EvalSymlinks(absPath)
			if err != nil {
				t.Log.ERROR.Printf("Cannot read symbolic link '%s', error was: %s", absPath, err)
				return nil
			}

			linkfi, err := t.Fs.Source.Stat(link)
			if err != nil {
				t.Log.ERROR.Printf("Cannot stat '%s', error was: %s", link, err)
				return nil
			}

			if !linkfi.Mode().IsRegular() {
				t.Log.ERROR.Printf("Symbolic links for directories not supported, skipping '%s'", absPath)
			}
			return nil
		}

		if !fi.IsDir() {
			if isDotFile(path) || isBackupFile(path) || isBaseTemplate(path) {
				return nil
			}

			var (
				workingDir = t.PathSpec.WorkingDir()
				themeDir   = t.PathSpec.GetThemeDir()
				layoutDir  = t.PathSpec.LayoutDir()
			)

			if themeDir != "" && strings.HasPrefix(absPath, themeDir) {
				workingDir = themeDir
				layoutDir = "layouts"
			}

			li := strings.LastIndex(path, layoutDir) + len(layoutDir) + 1
			relPath := path[li:]

			descriptor := output.TemplateLookupDescriptor{
				WorkingDir: workingDir,
				LayoutDir:  layoutDir,
				RelPath:    relPath,
				Prefix:     prefix,
				Theme:      t.PathSpec.Theme(),
				FileExists: func(filename string) (bool, error) {
					return helpers.Exists(filename, t.Fs.Source)
				},
				ContainsAny: func(filename string, subslices [][]byte) (bool, error) {
					return helpers.FileContainsAny(filename, subslices, t.Fs.Source)
				},
			}

			tplID, err := output.CreateTemplateNames(descriptor)
			if err != nil {
				t.Log.ERROR.Printf("Failed to resolve template in path %q: %s", path, err)

				return nil
			}

			if err := t.AddTemplateFile(tplID.Name, tplID.MasterFilename, tplID.OverlayFilename); err != nil {
				t.Log.ERROR.Printf("Failed to add template %q in path %q: %s", tplID.Name, path, err)
			}

		}
		return nil
	}
	if err := helpers.SymbolicWalk(t.Fs.Source, absPath, walker); err != nil {
		t.Log.ERROR.Printf("Failed to load templates: %s", err)
	}
}

func (t *GoHTMLTemplate) LoadTemplatesWithPrefix(absPath string, prefix string) {
	t.loadTemplates(absPath, prefix)
}

func (t *GoHTMLTemplate) LoadTemplates(absPath string) {
	t.loadTemplates(absPath, "")
}

func (t *GoHTMLTemplate) PrintErrors() {
	for i, e := range t.errors {
		t.Log.ERROR.Println(i, ":", e.err)
	}
}