package cnm

import (
	"io"
	"strings"
)

func init() {
	RegisterTextContentParser("", parseTextPlain)
	RegisterTextContentParser("plain", parseTextPlain)
	RegisterTextContentParser("pre", parseTextPre)
}

// Block represents an arbitrary CNM within the "content" top-level block.
type Block interface {
	// Name returns the name of the block.
	Name() string

	// Args returns the block arguments.
	Args() []string
	WriteIndent(w io.Writer, n int) error
}

// ContentBlock represents a block that holds other content blocks.
type ContentBlock struct {
	name     string
	args     []string
	children []Block
}

// WriteIndent writes the block header and its children indented by n tabs.
func (cb *ContentBlock) WriteIndent(w io.Writer, n int) error {
	ss := []string{Escape(cb.name)}
	ss = append(ss, cb.args...)
	if err := writeIndent(w, JoinEscape(ss), n); err != nil {
		return err
	}
	for _, ch := range cb.children {
		if err := ch.WriteIndent(w, n+1); err != nil {
			return err
		}
	}
	return nil
}

// NewContentBlock creates a new ContentBlock with a name and argument.
func NewContentBlock(name string, args ...string) *ContentBlock {
	var a []string
	for _, arg := range args {
		if arg != "" {
			a = append(a, arg)
		}
	}
	return &ContentBlock{name: name, args: a}
}

// Name returns the block's name.
func (cb *ContentBlock) Name() string {
	return cb.name
}

// Args returns the block arguments.
func (cb *ContentBlock) Args() []string {
	return cb.args
}

// Children returns the block's child blocks.
func (cb *ContentBlock) Children() []Block {
	return cb.children
}

// AppendChild adds a new child block to the end of the list of children.
func (cb *ContentBlock) AppendChild(block Block) {
	cb.children = append(cb.children, block)
}

func (cb *ContentBlock) parse(p *Parser, block *TokenBlock) (err error) {
	for err == nil {
		if !p.Empty() && p.Indent() <= block.Indent() {
			break
		}

		token := p.Block()
		if blk, ok := token.(*TokenBlock); ok {
			var b Block
			switch blk.Name {
			case "section":
				b, err = parseContentSection(p, blk)
			case "text":
				b, err = parseContentText(p, blk)
			case "raw":
				b, err = parseContentRaw(p, blk)
			case "list":
				b, err = parseContentList(p, blk)
			case "table":
				b, err = parseContentTable(p, blk)
			case "embed":
				b, err = parseContentEmbed(p, blk)
			default:
				err = parseUnknown(p, blk)
			}
			if b != nil {
				cb.AppendChild(b)
			}
		} else if err = p.Next(); err != nil {
			break
		}
	}
	return
}

// SectionBlock represents a "section" content block.
type SectionBlock struct {
	ContentBlock
}

// NewSectionBlock creates a new SectionBlock with a title.
func NewSectionBlock(title string) *SectionBlock {
	return &SectionBlock{*NewContentBlock("section", title)}
}

// Title returns the section block's title.
func (b *SectionBlock) Title() string { return strings.Join(b.args, " ") }

func parseContentSection(p *Parser, block *TokenBlock) (*SectionBlock, error) {
	sec := NewSectionBlock(strings.Join(block.Args, " "))
	if err := p.Next(); err != nil {
		return sec, err
	}
	return sec, sec.parse(p, block)
}

// TextBlock represents a "text" content block.
type TextBlock struct {
	// Format is the text format (first word of the block argument).
	Format string
	// Contents are the text contents.
	Contents TextContents
}

// NewTextBlock creates a new TextBlock containing arbitrary text contents.
func NewTextBlock(format string, contents TextContents) *TextBlock {
	return &TextBlock{format, contents}
}

// Name returns the block name "text".
func (t *TextBlock) Name() string { return "text" }

// Args returns the block's arguments (format).
func (t *TextBlock) Args() []string {
	if t.Format == "" {
		return nil
	}
	return []string{t.Format}
}

// WriteIndent writes the block header and its content indented by n tabs.
func (t *TextBlock) WriteIndent(w io.Writer, n int) error {
	s := t.Name()
	if t.Format != "" {
		s += " " + Escape(t.Format)
	}
	if err := writeIndent(w, s, n); err != nil {
		return err
	}
	if err := t.Contents.WriteIndent(w, n+1); err != nil {
		return err
	}
	return nil
}

func parseContentText(p *Parser, block *TokenBlock) (*TextBlock, error) {
	format := ""
	if len(block.Args) >= 1 {
		format = block.Args[0]
	}
	tb := NewTextBlock(format, nil)

	if err := p.Next(); err != nil {
		return tb, err
	}

	var err error
	tb.Contents, err = parseTextFormat(p, block, tb.Format)

	return tb, err
}

func parseTextFormat(p *Parser, block *TokenBlock, format string) (TextContents, error) {
	if parser := GetTextContentParser(format); parser != nil {
		return parser(p, block)
	}
	r, err := parseContentRaw(p, block)
	return TextPreContents{r.Contents}, err
}

// TextContents represents the textual contents of a text block.
type TextContents interface {
	WriteIndent(w io.Writer, n int) error
}

// TextContentParser parses text content in a text block.
type TextContentParser func(p *Parser, block *TokenBlock) (TextContents, error)

var textContentParsers = map[string]TextContentParser{}

// GetTextContentParser retrieves a text content parser or nil if it doesn't
// exist.
func GetTextContentParser(name string) TextContentParser {
	return textContentParsers[name]
}

// RegisterTextContentParser registers a new text content parser for a format.
func RegisterTextContentParser(name string, parser TextContentParser) {
	if parser == nil {
		delete(textContentParsers, name)
	} else {
		textContentParsers[name] = parser
	}
}

// TextPlainContents represents a list of simple text paragraphs.
type TextPlainContents struct {
	// Paragraphs is a list of simple text paragraphs.
	Paragraphs []string
}

// WriteIndent writes the plain text content indented by n tabs.
func (t TextPlainContents) WriteIndent(w io.Writer, n int) error {
	for i, p := range t.Paragraphs {
		if i != 0 {
			if err := writeIndent(w, "", 0); err != nil {
				return err
			}
		}
		if err := writeIndent(w, Escape(p), n); err != nil {
			return err
		}
	}
	return nil
}

// NewTextPlainBlock creates a new TextBlock containing TextPlainContents.
func NewTextPlainBlock(paragraphs []string) *TextBlock {
	par := make([]string, len(paragraphs))
	copy(par, paragraphs)
	return NewTextBlock("", TextPlainContents{par})
}

func parseTextPlain(p *Parser, block *TokenBlock) (TextContents, error) {
	txt := TextPlainContents{}
	paragraph := ""
	var err error
	for err == nil {
		if !p.Empty() && p.Indent() <= block.Indent() {
			break
		}

		token := p.SimpleText()
		end := false
		if text, ok := token.(*TokenSimpleText); ok {
			if text.Text == "" {
				end = true
			} else if paragraph == "" {
				paragraph = text.Text
			} else {
				paragraph += " " + text.Text
			}
		} else if _, ok := token.(*TokenEmptyLine); ok && paragraph != "" {
			end = true
		}
		if end {
			txt.Paragraphs = append(txt.Paragraphs, paragraph)
			paragraph = ""
		}
		err = p.Next()
	}
	if paragraph != "" {
		txt.Paragraphs = append(txt.Paragraphs, paragraph)
	}
	return txt, err
}

// TextPreContents represents preformatted contents of a text block.
type TextPreContents struct {
	// Text is the preformatted content.
	Text string
}

// WriteIndent writes the preformatted text content indented by n tabs.
func (t TextPreContents) WriteIndent(w io.Writer, n int) error {
	ss := strings.Split(t.Text, "\n")
	for _, s := range ss {
		if err := writeIndent(w, EscapeNonspace(s), n); err != nil {
			return err
		}
	}
	return nil
}

// NewTextPreBlock creates a new TextBlock containing TextPreContents.
func NewTextPreBlock(text string) *TextBlock {
	return NewTextBlock("", TextPreContents{text})
}

func parseTextPre(p *Parser, block *TokenBlock) (TextContents, error) {
	var lines []string
	var ls []string
	var err error
	for err == nil {
		if !p.Empty() && p.Indent() <= block.Indent() {
			break
		}

		token := p.RawText()
		if text, ok := token.(*TokenRawText); ok {
			if len(ls) > 0 {
				lines = append(lines, ls...)
				ls = ls[:0]
			}
			lines = append(lines, Unescape(text.Text))
		} else if _, ok := token.(*TokenEmptyLine); ok && len(lines) > 0 {
			ls = append(ls, "")
		}
		err = p.Next()
	}
	return TextPreContents{strings.Join(lines, "\n")}, err
}

// RawBlock represents a "raw" content block.
type RawBlock struct {
	// Syntax is the syntax of the block contents (first word of block argument)
	Syntax string

	// Contents is the raw content.
	Contents string
}

// Name returns the block name "raw".
func (r *RawBlock) Name() string { return "raw" }

// Args returns the block's arguments (syntax).
func (r *RawBlock) Args() []string {
	if r.Syntax == "" {
		return nil
	}
	return []string{r.Syntax}
}

// WriteIndent writes the raw content indented by n tabs.
func (r *RawBlock) WriteIndent(w io.Writer, n int) error {
	s := r.Name()
	if r.Syntax != "" {
		s += " " + Escape(r.Syntax)
	}
	if err := writeIndent(w, s, n); err != nil {
		return err
	}
	if r.Contents != "" {
		ss := strings.Split(r.Contents, "\n")
		for _, s := range ss {
			if err := writeIndent(w, s, n+1); err != nil {
				return err
			}
		}
	}
	return nil
}

func parseContentRaw(p *Parser, block *TokenBlock) (*RawBlock, error) {
	arg := ""
	if len(block.Args) > 0 {
		arg = block.Args[0]
	}
	rb := &RawBlock{arg, ""}

	if err := p.Next(); err != nil {
		return rb, err
	}

	var lines []string
	var ls []string
	var err error
	for err == nil {
		if !p.Empty() && p.Indent() <= block.Indent() {
			break
		}

		token := p.RawText()
		if text, ok := token.(*TokenRawText); ok {
			if len(ls) > 0 {
				lines = append(lines, ls...)
				ls = ls[:0]
			}
			lines = append(lines, text.Text)
		} else if _, ok := token.(*TokenEmptyLine); ok && len(lines) > 0 {
			ls = append(ls, "")
		}
		err = p.Next()
	}
	rb.Contents = strings.Join(lines, "\n")

	return rb, err
}

// ListBlock represents a "list" content block.
type ListBlock struct {
	ContentBlock
}

// NewListBlock creates a new ListBlock.
//
// If the ordered parameter is true, the list is created in "ordered" mode.
func NewListBlock(ordered bool) *ListBlock {
	arg := ""
	if ordered {
		arg = "ordered"
	}
	return &ListBlock{*NewContentBlock("list", arg)}
}

// Ordered returns true if the list is in ordered mode (first word of the
// block argument is "ordered").
func (b *ListBlock) Ordered() bool {
	return len(b.args) >= 1 && b.args[0] == "ordered"
}

func parseContentList(p *Parser, block *TokenBlock) (*ListBlock, error) {
	list := NewListBlock(false)
	list.args = block.Args
	if err := p.Next(); err != nil {
		return list, err
	}
	return list, list.parse(p, block)
}

// TableBlock represents a "table" content block.
type TableBlock struct {
	rows []Block
}

// NewTableBlock creates a new TableBlock.
func NewTableBlock() *TableBlock {
	return &TableBlock{}
}

// Name returns the block name "table".
func (t *TableBlock) Name() string {
	return "table"
}

// Args returns the block's nil arguments.
func (t *TableBlock) Args() []string {
	return nil
}

// WriteIndent writes the table header and contents indented by n tabs.
func (t *TableBlock) WriteIndent(w io.Writer, n int) error {
	if err := writeIndent(w, t.Name(), n); err != nil {
		return err
	}
	for _, row := range t.rows {
		if err := row.WriteIndent(w, n+1); err != nil {
			return err
		}
	}
	return nil
}

// Rows returns the table's rows.
func (t *TableBlock) Rows() []Block {
	return t.rows
}

// AppendRow adds a new row to the end of the table.
func (t *TableBlock) AppendRow(row Block) {
	t.rows = append(t.rows, row)
}

func (t *TableBlock) parse(p *Parser, block *TokenBlock) (err error) {
	for err == nil {
		if !p.Empty() && p.Indent() <= block.Indent() {
			break
		}

		token := p.Block()
		if blk, ok := token.(*TokenBlock); ok {
			var b Block
			switch blk.Name {
			case "row":
				b, err = parseTableRow(p, blk)
			case "header":
				b, err = parseTableHeader(p, blk)
			default:
				err = parseUnknown(p, blk)
			}
			if b != nil {
				t.AppendRow(b)
			}
		} else if err = p.Next(); err != nil {
			break
		}
	}
	return
}

func parseContentTable(p *Parser, block *TokenBlock) (*TableBlock, error) {
	table := NewTableBlock()
	if err := p.Next(); err != nil {
		return table, err
	}
	return table, table.parse(p, block)
}

// RowBlock represents a "row" table block.
type RowBlock struct {
	ContentBlock
}

// NewRowBlock creates a new RowBlock.
func NewRowBlock() *RowBlock {
	return &RowBlock{*NewContentBlock("row", "")}
}

func parseTableRow(p *Parser, block *TokenBlock) (*RowBlock, error) {
	row := NewRowBlock()
	if err := p.Next(); err != nil {
		return row, err
	}
	return row, row.parse(p, block)
}

// HeaderBlock represents a "header" table block.
type HeaderBlock struct {
	ContentBlock
}

// NewHeaderBlock creates a new HeaderBlock.
func NewHeaderBlock() *HeaderBlock {
	return &HeaderBlock{*NewContentBlock("header", "")}
}

func parseTableHeader(p *Parser, block *TokenBlock) (*HeaderBlock, error) {
	hdr := NewHeaderBlock()
	if err := p.Next(); err != nil {
		return hdr, err
	}
	return hdr, hdr.parse(p, block)
}

// EmbedBlock represents an "embed" content block.
type EmbedBlock struct {
	// Type is the content type (first word of block argument).
	Type string

	// URL is the content URL (second word of the block argument).
	URL string

	// Description is the content description (block body as simple text).
	Description string
}

// Name returns the block name "embed".
func (e *EmbedBlock) Name() string { return "embed" }

// Args returns the block argument (type and URL).
func (e *EmbedBlock) Args() []string {
	if e.Type != "" && e.URL != "" {
		return []string{e.Type, e.URL}
	}
	return []string{e.Type}
}

// WriteIndent writes the embed block header and contents indented by n tabs.
func (e *EmbedBlock) WriteIndent(w io.Writer, n int) error {
	if e.URL == "" {
		return nil
	}

	s := e.Name() + " "
	if e.Type == "" {
		s += "*/*"
	} else {
		s += Escape(e.Type)
	}
	s += " " + Escape(e.URL)
	if err := writeIndent(w, s, n); err != nil {
		return err
	}
	if err := writeIndent(w, Escape(e.Description), n+1); err != nil {
		return err
	}
	return nil
}

func parseContentEmbed(p *Parser, block *TokenBlock) (*EmbedBlock, error) {
	embed := &EmbedBlock{}
	if len(block.Args) >= 1 {
		embed.Type = block.Args[0]
		if len(block.Args) >= 2 {
			embed.URL = block.Args[1]
		}
	}
	if err := p.Next(); err != nil {
		return embed, err
	}
	s, err := getSimpleText(p, block)
	embed.Description = s
	return embed, err
}