// Copyright © 2013 Steve Francia <spf@spf13.com>.
//
// Licensed under the Simple Public 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://opensource.org/licenses/Simple-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 (
	"bufio"
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"github.com/BurntSushi/toml"
	"github.com/theplant/blackfriday"
	"io"
	"html/template"
	"io/ioutil"
	"launchpad.net/goyaml"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"
	"unicode"
)

var _ = filepath.Base("")

type Page struct {
	Status          string
	Images          []string
	Content         template.HTML
	Summary         template.HTML
	RawMarkdown     string // TODO should be []byte
	Params          map[string]interface{}
	RenderedContent *bytes.Buffer
	contentType     string
	Draft           bool
	Aliases         []string
	Tmpl            Template
	Markup          string
	PageMeta
	File
	Position
	Node
}

type File struct {
	FileName, OutFile, Extension string
}

type PageMeta struct {
	WordCount      int
	FuzzyWordCount int
}

type Position struct {
	Prev *Page
	Next *Page
}

type Pages []*Page

func (p Pages) Len() int           { return len(p) }
func (p Pages) Less(i, j int) bool { return p[i].Date.Unix() > p[j].Date.Unix() }
func (p Pages) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }

// TODO eliminate unnecessary things
func (p Pages) Sort()             { sort.Sort(p) }
func (p Pages) Limit(n int) Pages { return p[0:n] }

// TODO abstract further to support loading from more
// than just files on disk. Should load reader (file, []byte)
func NewPage(filename string) *Page {
	page := Page{contentType: "",
		File:   File{FileName: filename, Extension: "html"},
		Node:   Node{Keywords: make([]string, 10, 30)},
		Params: make(map[string]interface{}),
		Markup: "md"}
	page.Date, _ = time.Parse("20060102", "20080101")
	page.guessSection()
	return &page
}

func (page *Page) Initalize() error {
	err := page.buildPageFromFile()
	if err != nil {
		return err
	}
	page.analyzePage()
	return nil
}

func (p *Page) guessSection() {
	if p.Section == "" {
		x := strings.Split(p.FileName, string(os.PathSeparator))
		if len(x) > 1 {
			if section := x[len(x)-2]; section != "content" {
				p.Section = section
			}
		}
	}
}

func (page *Page) Type() string {
	if page.contentType != "" {
		return page.contentType
	}
	page.guessSection()
	if x := page.Section; x != "" {
		return x
	}

	return "page"
}

func (page *Page) Layout(l ...string) string {
	layout := ""
	if len(l) == 0 {
		layout = "single"
	} else {
		layout = l[0]
	}

	if x := page.layout; x != "" {
		return x
	}

	return strings.ToLower(page.Type()) + "/" + layout + ".html"
}

func ReadFrom(buf io.Reader, name string) (page *Page, err error) {
	if len(name) == 0 {
		return nil, errors.New("Zero length page name")
	}

	p := NewPage(name)

	if err = p.parse(buf); err != nil {
		return
	}

	p.analyzePage()

	return p, nil
}

func (p *Page) analyzePage() {
	p.WordCount = TotalWords(p.RawMarkdown)
	p.FuzzyWordCount = int((p.WordCount+100)/100) * 100
}

func splitPageContent(data []byte, start string, end string) ([]string, []string) {
	lines := strings.Split(string(data), "\n")
	datum := lines[0:]

	var found = 0
	if start != end {
		for i, line := range lines {

			if strings.HasPrefix(line, start) {
				found += 1
			}

			if strings.HasPrefix(line, end) {
				found -= 1
			}

			if found == 0 {
				datum = lines[0 : i+1]
				lines = lines[i+1:]
				break
			}
		}
	}
	return datum, lines
}

func (p *Page) Permalink() template.HTML {
	baseUrl := string(p.Site.BaseUrl)
	section := strings.TrimSpace(p.Section)
	pSlug := strings.TrimSpace(p.Slug)
	pUrl := strings.TrimSpace(p.Url)
	var path string
	if len(pSlug) > 0 {
		if p.Site.Config.UglyUrls {
			path = section + "/" + p.Slug + "." + p.Extension
		} else {
			path = section + "/" + p.Slug + "/"
		}
	} else if len(pUrl) > 2 {
		path = pUrl
	} else {
		_, t := filepath.Split(p.FileName)
		if p.Site.Config.UglyUrls {
			x := replaceExtension(strings.TrimSpace(t), p.Extension)
			path = section + "/" + x
		} else {
			file, _ := fileExt(strings.TrimSpace(t))
			path = section + "/" + file
		}
	}
	return template.HTML(MakePermalink(baseUrl, path))
}

func (page *Page) handleTomlMetaData(datum []byte) (interface{}, error) {
	m := map[string]interface{}{}
	if _, err := toml.Decode(string(datum), &m); err != nil {
		return m, fmt.Errorf("Invalid TOML in %s \nError parsing page meta data: %s", page.FileName, err)
	}
	return m, nil
}

func (page *Page) handleYamlMetaData(datum []byte) (interface{}, error) {
	m := map[string]interface{}{}
	if err := goyaml.Unmarshal(datum, &m); err != nil {
		return m, fmt.Errorf("Invalid YAML in %s \nError parsing page meta data: %s", page.FileName, err)
	}
	return m, nil
}

func (page *Page) handleJsonMetaData(datum []byte) (interface{}, error) {
	var f interface{}
	if err := json.Unmarshal(datum, &f); err != nil {
		return f, fmt.Errorf("Invalid JSON in %v \nError parsing page meta data: %s", page.FileName, err)
	}
	return f, nil
}

func (page *Page) update(f interface{}) error {
	m := f.(map[string]interface{})

	for k, v := range m {
		switch strings.ToLower(k) {
		case "title":
			page.Title = interfaceToString(v)
		case "description":
			page.Description = interfaceToString(v)
		case "slug":
			page.Slug = Urlize(interfaceToString(v))
		case "url":
			if url := interfaceToString(v); strings.HasPrefix(url, "http://") || strings.HasPrefix(url, "https://") {
				return fmt.Errorf("Only relative urls are supported, %v provided", url)
			}
			page.Url = Urlize(interfaceToString(v))
		case "type":
			page.contentType = interfaceToString(v)
		case "keywords":
			page.Keywords = interfaceArrayToStringArray(v)
		case "date", "pubdate":
			page.Date = interfaceToStringToDate(v)
		case "draft":
			page.Draft = interfaceToBool(v)
		case "layout":
			page.layout = interfaceToString(v)
		case "markup":
			page.Markup = interfaceToString(v)
		case "aliases":
			page.Aliases = interfaceArrayToStringArray(v)
			for _, alias := range page.Aliases {
				if strings.HasPrefix(alias, "http://") || strings.HasPrefix(alias, "https://") {
					return fmt.Errorf("Only relative aliases are supported, %v provided", alias)
				}
			}
		case "status":
			page.Status = interfaceToString(v)
		default:
			// If not one of the explicit values, store in Params
			switch vv := v.(type) {
			case string: // handle string values
				page.Params[strings.ToLower(k)] = vv
			default: // handle array of strings as well
				switch vvv := vv.(type) {
				case []interface{}:
					var a = make([]string, len(vvv))
					for i, u := range vvv {
						a[i] = interfaceToString(u)
					}
					page.Params[strings.ToLower(k)] = a
				}
			}
		}
	}
	return nil

}

func (page *Page) GetParam(key string) interface{} {
	v := page.Params[strings.ToLower(key)]

	if v == nil {
		return nil
	}

	switch v.(type) {
	case string:
		return interfaceToString(v)
	case []string:
		return v
	}
	return nil
}

var ErrDetectingFrontMatter = errors.New("unable to detect front matter")
var ErrMatchingStartingFrontMatterDelimiter = errors.New("unable to match beginning front matter delimiter")
var ErrMatchingEndingFrontMatterDelimiter = errors.New("unable to match ending front matter delimiter")

func (page *Page) parseFrontMatter(data *bufio.Reader) (err error) {

	if err = checkEmpty(data); err != nil {
		return
	}

	var mark rune
	if mark, err = chompWhitespace(data); err != nil {
		return
	}

	f := page.detectFrontMatter(mark)
	if f == nil {
		return ErrDetectingFrontMatter
	}

	if found, err := beginFrontMatter(data, f); err != nil || !found {
		return ErrMatchingStartingFrontMatterDelimiter
	}

	var frontmatter = new(bytes.Buffer)
	for {
		line, _, err := data.ReadLine()
		if err != nil {
			if err == io.EOF {
				return ErrMatchingEndingFrontMatterDelimiter
			}
			return err
		}

		if bytes.Equal(line, f.markend) {
			if f.includeMark {
				frontmatter.Write(line)
			}
			break
		}

		frontmatter.Write(line)
		frontmatter.Write([]byte{'\n'})
	}

	metadata, err := f.parse(frontmatter.Bytes())
	if err != nil {
		return
	}

	if err = page.update(metadata); err != nil {
		return
	}

	return
}

func checkEmpty(data *bufio.Reader) (err error) {
	if _, _, err = data.ReadRune(); err != nil {
		return errors.New("unable to locate front matter")
	}
	if err = data.UnreadRune(); err != nil {
		return errors.New("unable to unread first charactor in page buffer.")
	}
	return
}

type frontmatterType struct {
	markstart, markend []byte
	parse              func([]byte) (interface{}, error)
	includeMark        bool
}

func (page *Page) detectFrontMatter(mark rune) (f *frontmatterType) {
	switch mark {
	case '-':
		return &frontmatterType{[]byte{'-', '-', '-'}, []byte{'-', '-', '-'}, page.handleYamlMetaData, false}
	case '+':
		return &frontmatterType{[]byte{'+', '+', '+'}, []byte{'+', '+', '+'}, page.handleTomlMetaData, false}
	case '{':
		return &frontmatterType{[]byte{'{'}, []byte{'}'}, page.handleJsonMetaData, true}
	default:
		return nil
	}
}

func beginFrontMatter(data *bufio.Reader, f *frontmatterType) (bool, error) {
	var err error
	var peek []byte
	if f.includeMark {
		peek, err = data.Peek(len(f.markstart))
	} else {
		peek = make([]byte, len(f.markstart))
		_, err = data.Read(peek)
	}
	if err != nil {
		return false, err
	}
	return bytes.Equal(peek, f.markstart), nil
}

func chompWhitespace(data *bufio.Reader) (r rune, err error) {
	for {
		r, _, err = data.ReadRune()
		if err != nil {
			return
		}
		if unicode.IsSpace(r) {
			continue
		}
		if err := data.UnreadRune(); err != nil {
			return r, errors.New("unable to unread first charactor in front matter.")
		}
		return r, nil
	}
}

func (p *Page) Render(layout ...string) template.HTML {
	curLayout := ""

	if len(layout) > 0 {
		curLayout = layout[0]
	}

	return template.HTML(string(p.ExecuteTemplate(curLayout).Bytes()))
}

func (p *Page) ExecuteTemplate(layout string) *bytes.Buffer {
	l := p.Layout(layout)
	buffer := new(bytes.Buffer)
	p.Tmpl.ExecuteTemplate(buffer, l, p)
	return buffer
}

func (page *Page) readFile() (data []byte, err error) {
	data, err = ioutil.ReadFile(page.FileName)
	if err != nil {
		return nil, err
	}
	return data, nil
}

func (page *Page) buildPageFromFile() error {
	f, err := os.Open(page.FileName)
	if err != nil {
		return err
	}
	return page.parse(bufio.NewReader(f))
}

func (page *Page) parse(reader io.Reader) error {
	data := bufio.NewReader(reader)

	err := page.parseFrontMatter(data)
	if err != nil {
		return err
	}

	switch page.Markup {
	case "md":
		page.convertMarkdown(data)
	case "rst":
		page.convertRestructuredText(data)
	}
	return nil
}

func (page *Page) convertMarkdown(lines io.Reader) {
	b := new(bytes.Buffer)
	b.ReadFrom(lines)
	content := b.Bytes()
	page.Content = template.HTML(string(blackfriday.MarkdownCommon(RemoveSummaryDivider(content))))
	summary, plain := getSummaryString(content)
	if plain {
		page.Summary = template.HTML(string(summary))
	} else {
		page.Summary = template.HTML(string(blackfriday.MarkdownCommon(summary)))
	}
}

func (page *Page) convertRestructuredText(lines io.Reader) {
	b := new(bytes.Buffer)
	b.ReadFrom(lines)
	content := b.Bytes()
	page.Content = template.HTML(getRstContent(content))
	summary, plain := getSummaryString(content)
	if plain {
		page.Summary = template.HTML(string(summary))
	} else {
		page.Summary = template.HTML(getRstContent(summary))
	}
}