// 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 (
	"errors"
	"fmt"
	"path/filepath"

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

	"strings"

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

var (
	// This should be the only list of valid extensions for content files.
	contentFileExtensions = []string{
		"html", "htm",
		"mdown", "markdown", "md",
		"asciidoc", "adoc", "ad",
		"rest", "rst",
		"mmark",
		"org",
		"pandoc", "pdc"}

	contentFileExtensionsSet map[string]bool
)

func init() {
	contentFileExtensionsSet = make(map[string]bool)
	for _, ext := range contentFileExtensions {
		contentFileExtensionsSet[ext] = true
	}
}

func newHandlerChain(s *Site) contentHandler {
	c := &contentHandlers{s: s}

	contentFlow := c.parsePage(
		c.handlePageContent(),
	)

	c.rootHandler = c.processFirstMatch(
		contentFlow,

		// Creates a file resource (image, CSS etc.) if there is a parent
		// page set on the current context.
		c.createResource(),

		// Everything that isn't handled above, will just be copied
		// to destination.
		c.copyFile(),
	)

	return c.rootHandler

}

type contentHandlers struct {
	s           *Site
	rootHandler contentHandler
}

func (c *contentHandlers) processFirstMatch(handlers ...contentHandler) func(ctx *handlerContext) handlerResult {
	return func(ctx *handlerContext) handlerResult {
		for _, h := range handlers {
			res := h(ctx)
			if res.handled || res.err != nil {
				return res
			}
		}
		return handlerResult{err: errors.New("no matching handler found")}
	}
}

type handlerContext struct {
	// These are the pages stored in Site.
	pages chan<- *pageState

	doNotAddToSiteCollections bool

	currentPage *pageState
	parentPage  *pageState

	bundle *bundleDir

	source *fileInfo

	// Relative path to the target.
	target string
}

func (c *handlerContext) ext() string {
	if c.currentPage != nil {
		return c.currentPage.contentMarkupType()
	}

	if c.bundle != nil {
		return c.bundle.fi.Ext()
	} else {
		return c.source.Ext()
	}
}

func (c *handlerContext) targetPath() string {
	if c.target != "" {
		return c.target
	}

	return c.source.Filename()
}

func (c *handlerContext) file() *fileInfo {
	if c.bundle != nil {
		return c.bundle.fi
	}

	return c.source
}

// Create a copy with the current context as its parent.
func (c handlerContext) childCtx(fi *fileInfo) *handlerContext {
	if c.currentPage == nil {
		panic("Need a Page to create a child context")
	}

	c.target = strings.TrimPrefix(fi.Path(), c.bundle.fi.Dir())
	c.source = fi

	c.doNotAddToSiteCollections = c.bundle != nil && c.bundle.tp != bundleBranch

	c.bundle = nil

	c.parentPage = c.currentPage
	c.currentPage = nil

	return &c
}

func (c *handlerContext) supports(exts ...string) bool {
	ext := c.ext()
	for _, s := range exts {
		if s == ext {
			return true
		}
	}

	return false
}

func (c *handlerContext) isContentFile() bool {
	return contentFileExtensionsSet[c.ext()]
}

type (
	handlerResult struct {
		err     error
		handled bool
		result  interface{}
	}

	contentHandler func(ctx *handlerContext) handlerResult
)

var (
	notHandled handlerResult
)

func (c *contentHandlers) parsePage(h contentHandler) contentHandler {
	return func(ctx *handlerContext) handlerResult {
		if !ctx.isContentFile() {
			return notHandled
		}

		result := handlerResult{handled: true}
		fi := ctx.file()

		content := func() (hugio.ReadSeekCloser, error) {
			f, err := fi.Open()
			if err != nil {
				return nil, fmt.Errorf("failed to open content file %q: %s", fi.Filename(), err)
			}
			return f, nil
		}

		ps, err := newPageWithContent(fi, c.s, content)
		if err != nil {
			return handlerResult{err: err}
		}

		if !c.s.shouldBuild(ps) {
			if !ctx.doNotAddToSiteCollections {
				ctx.pages <- ps
			}
			return result
		}

		ctx.currentPage = ps

		if ctx.bundle != nil {
			// Add the bundled files
			for _, fi := range ctx.bundle.resources {
				childCtx := ctx.childCtx(fi)
				res := c.rootHandler(childCtx)
				if res.err != nil {
					return res
				}
				if res.result != nil {
					switch resv := res.result.(type) {
					case *pageState:
						resv.m.resourcePath = filepath.ToSlash(childCtx.target)
						resv.parent = ps
						ps.addResources(resv)
					case resource.Resource:
						ps.addResources(resv)

					default:
						panic("Unknown type")
					}
				}
			}
		}

		return h(ctx)
	}
}

func (c *contentHandlers) handlePageContent() contentHandler {
	return func(ctx *handlerContext) handlerResult {
		p := ctx.currentPage

		if !ctx.doNotAddToSiteCollections {
			ctx.pages <- p
		}

		return handlerResult{handled: true, result: p}
	}
}

func (c *contentHandlers) createResource() contentHandler {
	return func(ctx *handlerContext) handlerResult {
		if ctx.parentPage == nil {
			return notHandled
		}

		// TODO(bep) consolidate with multihost logic + clean up
		outputFormats := ctx.parentPage.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)

		}

		resource, err := c.s.ResourceSpec.New(
			resources.ResourceSourceDescriptor{
				TargetPaths:       ctx.parentPage.getTargetPaths,
				SourceFile:        ctx.source,
				RelTargetFilename: ctx.target,
				TargetBasePaths:   targetBasePaths,
			})

		return handlerResult{err: err, handled: true, result: resource}
	}
}

func (c *contentHandlers) copyFile() contentHandler {
	return func(ctx *handlerContext) handlerResult {
		f, err := c.s.BaseFs.Content.Fs.Open(ctx.source.Filename())
		if err != nil {
			err := fmt.Errorf("failed to open file in copyFile: %s", err)
			return handlerResult{err: err}
		}

		target := ctx.targetPath()

		defer f.Close()
		if err := c.s.publish(&c.s.PathSpec.ProcessingStats.Files, target, f); err != nil {
			return handlerResult{err: err}
		}

		return handlerResult{handled: true}
	}
}