package treerack

import (
	"bufio"
	"errors"
	"fmt"
	"io"
)

type CommitType int

const (
	None  CommitType = 0
	Alias CommitType = 1 << iota
	Whitespace
	NoWhitespace
	Documentation
	Root
)

type SequenceItem struct {
	Name     string
	Min, Max int // 0,0 considered as 1,1, x,0 considered as x,-1
}

type Syntax struct {
	registry     *registry
	initialized  bool
	initFailed   bool
	explicitRoot bool
	root         definition
	parser       parser
	builder      builder
}

var (
	ErrSyntaxInitialized       = errors.New("syntax initialized")
	ErrInitFailed              = errors.New("init failed")
	ErrNoParsersDefined        = errors.New("no parsers defined")
	ErrInvalidInput            = errors.New("invalid input")
	ErrInvalidUnicodeCharacter = errors.New("invalid unicode character")
	ErrInvalidEscapeCharacter  = errors.New("invalid escape character")
	ErrUnexpectedCharacter     = errors.New("unexpected character")
	ErrInvalidSyntax           = errors.New("invalid syntax")
	ErrRootAlias               = errors.New("root node cannot be an alias")
	ErrRootWhitespace          = errors.New("root node cannot be a whitespace")
	ErrNotImplemented          = errors.New("not implemented")
	ErrMultipleRoots           = errors.New("multiple roots")
	ErrInvalidSymbolName       = errors.New("invalid symbol name")
)

const symbolChars = "^\\\\ \\n\\t\\b\\f\\r\\v/.\\[\\]\\\"{}\\^+*?|():=;"

func parseSymbolChars(c []rune) []rune {
	_, chars, _, err := parseClass(c)
	if err != nil {
		panic(err)
	}

	return chars
}

var symbolCharRunes = parseSymbolChars([]rune(symbolChars))

func duplicateDefinition(name string) error {
	return fmt.Errorf("duplicate definition: %s", name)
}

func isValidSymbol(n string) bool {
	runes := []rune(n)
	for _, r := range runes {
		if !matchChars(symbolCharRunes, nil, true, r) {
			return false
		}
	}

	return true

}

func (s *Syntax) register(d definition) error {
	if s.initialized {
		return ErrSyntaxInitialized
	}

	if s.registry == nil {
		s.registry = newRegistry()
	}

	if d.commitType()&Root != 0 {
		if s.explicitRoot {
			return ErrMultipleRoots
		}

		if s.root != nil {
			s.root.setCommitType(s.root.commitType() &^ Root)
		}

		s.root = d
		s.root.setCommitType(s.root.commitType() | Root)
		s.explicitRoot = true
	} else if !s.explicitRoot {
		if s.root != nil {
			s.root.setCommitType(s.root.commitType() &^ Root)
		}

		s.root = d
		s.root.setCommitType(s.root.commitType() | Root)
	}

	// TODO: verify that definition names match the symbol criteria, or figure a better naming for the
	// whitespace

	return s.registry.setDefinition(d)
}

func (s *Syntax) anyChar(name string, ct CommitType) error {
	return s.class(name, ct, true, nil, nil)
}

func (s *Syntax) AnyChar(name string, ct CommitType) error {
	if !isValidSymbol(name) {
		return ErrInvalidSymbolName
	}

	return s.anyChar(name, ct)
}

func childName(name string, childIndex int) string {
	return fmt.Sprintf("%s:%d", name, childIndex)
}

func namesToSequenceItems(n []string) []SequenceItem {
	si := make([]SequenceItem, len(n))
	for i := range n {
		si[i] = SequenceItem{Name: n[i]}
	}

	return si
}

func (s *Syntax) class(name string, ct CommitType, not bool, chars []rune, ranges [][]rune) error {
	cname := childName(name, 0)
	if err := s.register(newChar(cname, not, chars, ranges)); err != nil {
		return err
	}

	return s.sequence(name, ct, SequenceItem{Name: cname})
}

func (s *Syntax) Class(name string, ct CommitType, not bool, chars []rune, ranges [][]rune) error {
	if !isValidSymbol(name) {
		return ErrInvalidSymbolName
	}

	return s.class(name, ct, not, chars, ranges)
}

func (s *Syntax) charSequence(name string, ct CommitType, chars []rune) error {
	var refs []string
	for i, ci := range chars {
		ref := childName(name, i)
		refs = append(refs, ref)
		if err := s.register(newChar(ref, false, []rune{ci}, nil)); err != nil {
			return err
		}
	}

	return s.sequence(name, ct|NoWhitespace, namesToSequenceItems(refs)...)
}

func (s *Syntax) CharSequence(name string, ct CommitType, chars []rune) error {
	if !isValidSymbol(name) {
		return ErrInvalidSymbolName
	}

	return s.charSequence(name, ct, chars)
}

func (s *Syntax) sequence(name string, ct CommitType, items ...SequenceItem) error {
	return s.register(newSequence(name, ct, items))
}

func (s *Syntax) Sequence(name string, ct CommitType, items ...SequenceItem) error {
	if !isValidSymbol(name) {
		return ErrInvalidSymbolName
	}

	return s.sequence(name, ct, items...)
}

func (s *Syntax) choice(name string, ct CommitType, elements ...string) error {
	return s.register(newChoice(name, ct, elements))
}

func (s *Syntax) Choice(name string, ct CommitType, elements ...string) error {
	if !isValidSymbol(name) {
		return ErrInvalidSymbolName
	}

	return s.choice(name, ct, elements...)
}

func (s *Syntax) Read(r io.Reader) error {
	if s.initialized {
		return ErrSyntaxInitialized
	}

	return ErrNotImplemented
}

// TODO: why normalization failed?

func (s *Syntax) Init() error {
	if s.initFailed {
		return ErrInitFailed
	}

	if s.initialized {
		return nil
	}

	if s.root == nil {
		return ErrNoParsersDefined
	}

	if s.root.commitType()&Alias != 0 {
		return ErrRootAlias
	}

	if s.root.commitType()&Whitespace != 0 {
		return ErrRootWhitespace
	}

	s.registry = initWhitespace(s.registry)

	for _, def := range s.registry.definitions {
		if def.commitType()&Root != 0 {
			s.root = def
			break
		}
	}

	if err := s.root.validate(s.registry, &idSet{}); err != nil {
		return err
	}

	if err := s.root.normalize(s.registry, &idSet{}); err != nil {
		return err
	}

	for _, p := range s.registry.definitions {
		p.init(s.registry)
	}

	var err error
	s.parser, err = s.root.parser(s.registry, &idSet{})
	if err != nil {
		s.initFailed = true
		return err
	}

	s.builder = s.root.builder()
	s.initialized = true
	return nil
}

func (s *Syntax) Generate(w io.Writer) error {
	if err := s.Init(); err != nil {
		return err
	}

	return ErrNotImplemented
}

// TODO: optimize top sequences to save memory, or just support streaming, or combine the two

func (s *Syntax) Parse(r io.Reader) (*Node, error) {
	if err := s.Init(); err != nil {
		return nil, err
	}

	c := newContext(bufio.NewReader(r))
	if err := parse(s.parser, c); err != nil {
		return nil, err
	}

	return build(s.builder, c), nil
}