package jdr

import (
	"encoding/xml"
	"html/template"

	"errors"
	"log"
	"os"
)

// Page represents a page of a character sheet.
type Page struct {
	Items []SheetItem
}

// ToHTML transforms a Page into a HTML code.
// This HTML code is embeddable into the character sheet webpage
func (page *Page) ToHTML() template.HTML {
	ret := ""

	for _, item := range page.Items {
		ret += string(item.ToHTML())
	}

	return template.HTML(ret)
}

// SheetItem represents an item in the character sheet (either a structural element or a value)
type SheetItem interface {
	Name() string
	ToHTML() template.HTML
}

// Block represents a SheetItem that contains other SheetItems.
// It is used as a structural element to group values together.
type Block struct {
	name  string
	Items []SheetItem
}

// Name of the block (possibly empty if the block is unnamed)
func (block *Block) Name() string {
	return block.name
}

// ToHTML transforms a Block into a HTML code.
func (block *Block) ToHTML() template.HTML {
	begin := `<fieldset>`
	legend := `<legend>` + template.HTMLEscapeString(block.Name()) + `</legend>`
	end := `</fieldset>`

	ret := template.HTML(begin)
	if block.Name() != "" {
		ret += template.HTML(legend)
	}

	for _, item := range block.Items {
		ret += item.ToHTML()
	}
	ret += template.HTML(end)

	return ret
}

// Variable is a value in the character sheet, such as the name of the character, or its XP count
type Variable struct {
	Type VariableType
	name string
}

// Name of the variable
func (v *Variable) Name() string {
	return v.name
}

// ToHTML transforms a Variable into a HTML code
func (v *Variable) ToHTML() template.HTML {
	label := ""
	if v.name != "" {
		label = `<label>` + template.HTMLEscapeString(v.name) + `</label>`
	}

	html, err := v.Type.ToHTML(v.Type.DefaultValue())
	if err != nil {
		log.Fatal(err)
	}

	return template.HTML(label) + html + template.HTML(`<br/>`)
}

// CharacterSheet is a role-play character sheet.
// It is structured in Pages, Blocks and Variables
type CharacterSheet struct {
	types map[string]VariableType
	Pages []*Page
}

// Script renders the Javascript code necessary to render the character sheet web page interactive
func (cs *CharacterSheet) Script() template.JS {
	return template.JS("")
}

// Render the CharacterSheet into an embeddable HTML code
func (cs *CharacterSheet) Render() template.HTML {
	ret := template.HTML("")

	for _, page := range cs.Pages {
		ret += page.ToHTML()
	}

	return ret
}

// AddType adds a custom variable type to the character sheet
func (cs *CharacterSheet) AddType(t VariableType) {
	//create the type array if it doesn't exist yet
	if cs.types == nil {
		cs.types = make(map[string]VariableType)
	}

	name := t.Name()
	cs.types[name] = t
}

// AddDefaultTypes adds the default variable types to the character sheet
func (cs *CharacterSheet) AddDefaultTypes() {
	cs.AddType(&VariableType_bool{})
	cs.AddType(&VariableType_int{})
	cs.AddType(&VariableType_float{})
	cs.AddType(&VariableType_string{})
	cs.AddType(&VariableType_d{})
}

// getType searches into the types (default & customs) of a character sheet for one matching "typename"
func (cs *CharacterSheet) getType(typename string) (VariableType, error) {
	t, ok := cs.types[typename]
	if !ok {
		return &VariableType_badType{}, errors.New("unknown type \"" + typename + "\"")
	}

	return t, nil
}

// xmlNode is a temporary structure used for parsing the character sheet XML file
// without knowing its structure à priori
type xmlNode struct {
	XMLName xml.Name
	Attrs   []xml.Attr `xml:"-"`
	Content []byte     `xml:",innerxml"`
	Nodes   []xmlNode  `xml:",any"`
}

func (n *xmlNode) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	n.Attrs = start.Attr
	type node xmlNode

	return d.DecodeElement((*node)(n), &start)
}

// The parseVariable function parses a Variable value from a XML node.
// The variable type is inferred from the "type" attribute of the node.
// If this attribute is omitted, the type of the variable must be given through the
// "defaults" parameter to avoid a parsing error.
// If this attribute is specified, the "defaults" parameter will be unused and may be nil
func parseVariable(root xmlNode, sheet *CharacterSheet, defaults *Variable) (*Variable, error) {
	ret := &Variable{}

	typeOk := false
	nameOk := false

	//parsing default values
	if defaults != nil {
		switch defaults.Type.(type) {
		case *VariableType_badType:
			typeOk = false
		default:
			typeOk = true
			ret.Type = defaults.Type
		}
	}

	//iterating on the attributes
	for i := 0; i < len(root.Attrs); i++ {
		attrName := root.Attrs[i].Name.Local
		attrVal := root.Attrs[i].Value

		switch attrName {
		case "type":
			t, err := sheet.getType(attrVal)
			if err != nil {
				return nil, err
			}
			ret.Type = t
			typeOk = true
		case "name":
			ret.name = attrVal
			nameOk = true
		}
	}

	//check if no parse error
	if !nameOk {
		return nil, errors.New("Unnamed variable")
	}
	if !typeOk {
		return nil, errors.New("No type provided for variable \"" + ret.Name() + "\"")
	}

	return ret, nil
}

func parseBlock(root xmlNode, sheet *CharacterSheet) (*Block, error) {
	ret := &Block{}

	for i := 0; i < len(root.Attrs); i++ {
		attrName := root.Attrs[i].Name.Local
		attrVal := root.Attrs[i].Value

		switch attrName {
		case "name":
			ret.name = attrVal
		}
	}

	for i := 0; i < len(root.Nodes); i++ {
		items, err := parseItem(root.Nodes[i], sheet)
		if err != nil {
			return nil, err
		}

		for _, item := range items {
			ret.Items = append(ret.Items, item)
		}
	}

	return ret, nil
}

func parseVariableGroup(root xmlNode, sheet *CharacterSheet, defaults *Variable) ([]*Variable, error) {
	ret := []*Variable{}

	typeOk := false
	if defaults == nil {
		defaults = &Variable{}
	} else {
		typeOk = true
	}

	for i := 0; i < len(root.Attrs); i++ {
		attrName := root.Attrs[i].Name.Local
		attrVal := root.Attrs[i].Value

		switch attrName {
		case "default-type":
			t, err := sheet.getType(attrVal)
			if err != nil {
				return nil, err
			}
			defaults.Type = t
			typeOk = true
		}
	}

	if !typeOk {
		defaults.Type = &VariableType_badType{}
	}

	for i := 0; i < len(root.Nodes); i++ {
		node := root.Nodes[i]

		switch node.XMLName.Local {
		case "variable":
			item, err := parseVariable(node, sheet, defaults)
			if err != nil {
				return nil, err
			}

			ret = append(ret, item)
		case "variable-group":
			items, err := parseVariableGroup(node, sheet, defaults)
			if err != nil {
				return nil, err
			}

			for j := 0; j < len(items); j++ {
				ret = append(ret, items[j])
			}

		default:
			return nil, errors.New("Unknown variable-group item: \"" + node.XMLName.Local + "\"")
		}
	}

	return ret, nil
}

func parseItem(root xmlNode, sheet *CharacterSheet) ([]SheetItem, error) {
	switch root.XMLName.Local {
	case "block":
		block, err := parseBlock(root, sheet)
		if err != nil {
			return nil, err
		}

		return []SheetItem{block}, nil
	case "variable":
		variable, err := parseVariable(root, sheet, nil)
		if err != nil {
			return nil, err
		}

		return []SheetItem{variable}, err
	case "variable-group":
		variables, err := parseVariableGroup(root, sheet, nil)
		if err != nil {
			return nil, err
		}

		items := make([]SheetItem, len(variables))
		for i, v := range variables {
			items[i] = SheetItem(v)
		}
		return items, nil
	default:
		return nil, errors.New("Unknown item: " + root.XMLName.Local)
	}
}

func parsePage(root xmlNode, sheet *CharacterSheet) (*Page, error) {
	ret := &Page{}

	for i := 0; i < len(root.Nodes); i++ {
		items, err := parseItem(root.Nodes[i], sheet)
		if err != nil {
			return nil, err
		}

		for _, item := range items {
			ret.Items = append(ret.Items, item)
		}
	}

	return ret, nil
}

func parseSheet(root xmlNode) (*CharacterSheet, error) {
	if root.XMLName.Local != "jdr-desc" {
		return nil, errors.New("Wrong root node")
	}

	sheet := &CharacterSheet{}
	sheet.AddDefaultTypes()
	for i := 0; i < len(root.Nodes); i++ {
		node := root.Nodes[i]

		switch node.XMLName.Local {
		case "custom-types":
			err := parseCustomTypes(node, sheet)
			if err != nil {
				return nil, err
			}

		case "page":
			page, err := parsePage(node, sheet)
			if err != nil {
				return nil, err
			}
			sheet.Pages = append(sheet.Pages, page)

		default:
			return nil, errors.New("Wrong format")
		}
	}

	return sheet, nil
}

// ReadCharacterSheet opens a character sheet XML file
// and parses the XML to get a CharacterSheet struct
func ReadCharacterSheet(filename string) (*CharacterSheet, error) {
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	decoder := xml.NewDecoder(file)
	var n xmlNode
	err = decoder.Decode(&n)
	if err != nil {
		return nil, err
	}

	sheet, err := parseSheet(n)
	if err != nil {
		return nil, err
	}
	return sheet, nil
}