package tre

import (
	"encoding/binary"
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"sort"
)



type CharBlock struct {
	From []byte
	To   []byte
}

type cpRange struct {
	from rune
	to   rune
}



func (b *CharBlock) String() string {
	var s strings.Builder
	fmt.Fprint(&s, "<")
	fmt.Fprintf(&s, "%X", b.From[0])
	for i := 1; i < len(b.From); i++ {
		fmt.Fprintf(&s, " %X", b.From[i])
	}
	fmt.Fprint(&s, "..")
	fmt.Fprintf(&s, "%X", b.To[0])
	for i := 1; i < len(b.To); i++ {
		fmt.Fprintf(&s, " %X", b.To[i])
	}
	fmt.Fprint(&s, ">")
	return s.String()
}

func GenCharBlocks(from, to rune) ([]*CharBlock, error) {
	rs, err := splitCodePoint(from, to)
	if err != nil {
		return nil, err
	}

	blks := make([]*CharBlock, len(rs))
	for i, r := range rs {
		blks[i] = &CharBlock{
			From: []byte(string(r.from)),
			To:   []byte(string(r.to)),
		}
	}

	return blks, nil
}

/// `splitCodePoint` splits a code point range represented by <from..to> into
/// some blocks.  The code points that the block contains will be a continuous
/// byte sequence when encoded into UTF-8.  For instance, this function splits
/// <U+0000..U+07FF> into <U+0000..U+007F> and <U+0080..U+07FF> because
/// <U+0000..U+07FF> is continuous on the code point but non-continuous in the
/// UTF-8 byte sequence (In UTF-8, <U+0000..U+007F> is encoded <00..7F>, and
/// <U+0080..U+07FF> is encoded <C2 80..DF BF>).
///
/// The blocks don't contain surrogate code points <U+D800..U+DFFF> because byte
/// sequences encoding them are ill-formed in UTF-8.  For instance,
/// <U+D000..U+FFFF> is split into <U+D000..U+D7FF> and <U+E000..U+FFFF>.
/// However, when `from` or `to` itself is the surrogate code point, this
/// function returns an error.
func splitCodePoint(from, to rune) ([]*cpRange, error) {
	if from > to {
		return nil, fmt.Errorf(
			"code point range must be from <= to: U+%X..U+%X",
			from,
			to,
		)
	}
	if from < 0x0000 || from > 0x10ffff || to < 0x0000 || to > 0x10ffff {
		return nil, fmt.Errorf(
			"code point must be >=U+0000 and <=U+10FFFF:" +
				"U+%X..U+%X",
			from,
			to,
		)
	}
	// https://www.unicode.org/versions/Unicode13.0.0/ch03.pdf
	//  > 3.9 Unicode Encoding Forms
	//   > UTF-8 D92
	//    > Because surrogate code points are not Unicode scalar values,
	//    > any UTF-8 byte sequence that would otherwise
	//    > map to code points U+D800..U+DFFF is ill-formed.
	if from >= 0xd800 && from <= 0xdfff || to >= 0xd800 && to <= 0xdfff {
		return nil, fmt.Errorf(
			"surrogate code points U+D800..U+DFFF " +
				"are not allowed in UTF-8: U+%X..U+%X",
			from,
			to,
		)
	}

	in := &cpRange{
		from: from,
		to:   to,
	}
	var rs []*cpRange
	for in.from <= in.to {
		r := &cpRange{
			from: in.from,
			to:   in.to,
		}
		// https://www.unicode.org/versions/Unicode13.0.0/ch03.pdf
		//  > 3.9 Unicode Encoding Forms
		//   > UTF-8 Table 3-7.
		//    > Well-Formed UTF-8 Byte Sequences
		switch {
		case in.from <= 0x007f && in.to > 0x007f:
			r.to = 0x007f
		case in.from <= 0x07ff && in.to > 0x07ff:
			r.to = 0x07ff
		case in.from <= 0x0fff && in.to > 0x0fff:
			r.to = 0x0fff
		case in.from <= 0xcfff && in.to > 0xcfff:
			r.to = 0xcfff
		case in.from <= 0xd7ff && in.to > 0xd7ff:
			r.to = 0xd7ff
		case in.from <= 0xffff && in.to > 0xffff:
			r.to = 0xffff
		case in.from <= 0x3ffff && in.to > 0x3ffff:
			r.to = 0x3ffff
		case in.from <= 0xfffff && in.to > 0xfffff:
			r.to = 0xfffff
		}
		rs = append(rs, r)
		in.from = r.to + 1

		// Skip surrogate code points U+D800..U+DFFF.
		if in.from >= 0xd800 && in.from <= 0xdfff {
			in.from = 0xe000
		}
	}
	return rs, nil
}



type OriginalTable struct {
	entries  []int
	rowCount int
	colCount int
}

func NewOriginalTable(entries []int, colCount int) (*OriginalTable, error) {
	if len(entries) == 0 {
		return nil, fmt.Errorf("enries is empty")
	}
	if colCount <= 0 {
		return nil, fmt.Errorf("colCount must be >=1")
	}
	if len(entries)%colCount != 0 {
		return nil, fmt.Errorf("entries length or column count are incorrect; entries length: %v, column count: %v", len(entries), colCount)
	}

	return &OriginalTable{
		entries:  entries,
		rowCount: len(entries) / colCount,
		colCount: colCount,
	}, nil
}

type Compressor interface {
	Compress(orig *OriginalTable) error
	Lookup(row, col int) (int, error)
	OriginalTableSize() (int, int)
}

var (
	_ Compressor = &CompressorUniqueEntriesTable{}
	_ Compressor = &CompressorRowDisplacementTable{}
)

type CompressorUniqueEntriesTable struct {
	UniqueEntries    []int
	RowNums          []int
	OriginalRowCount int
	OriginalColCount int
}

func NewCompressorUniqueEntriesTable() *CompressorUniqueEntriesTable {
	return &CompressorUniqueEntriesTable{}
}

func (tab *CompressorUniqueEntriesTable) Lookup(row, col int) (int, error) {
	if row < 0 || row >= tab.OriginalRowCount || col < 0 || col >= tab.OriginalColCount {
		return 0, fmt.Errorf("indexes are out of range: [%v, %v]", row, col)
	}
	return tab.UniqueEntries[tab.RowNums[row]*tab.OriginalColCount+col], nil
}

func (tab *CompressorUniqueEntriesTable) OriginalTableSize() (int, int) {
	return tab.OriginalRowCount, tab.OriginalColCount
}

func (tab *CompressorUniqueEntriesTable) Compress(orig *OriginalTable) error {
	var uniqueEntries []int
	rowNums := make([]int, orig.rowCount)
	hash2RowNum := map[string]int{}
	nextRowNum := 0
	for row := 0; row < orig.rowCount; row++ {
		var rowHash string
		{
			buf := make([]byte, 0, orig.colCount*8)
			for col := 0; col < orig.colCount; col++ {
				b := make([]byte, 8)
				binary.PutUvarint(b, uint64(orig.entries[row*orig.colCount+col]))
				buf = append(buf, b...)
			}
			rowHash = string(buf)
		}
		rowNum, ok := hash2RowNum[rowHash]
		if !ok {
			rowNum = nextRowNum
			nextRowNum++
			hash2RowNum[rowHash] = rowNum
			start := row * orig.colCount
			entry := append([]int{}, orig.entries[start:start+orig.colCount]...)
			uniqueEntries = append(uniqueEntries, entry...)
		}
		rowNums[row] = rowNum
	}

	tab.UniqueEntries = uniqueEntries
	tab.RowNums = rowNums
	tab.OriginalRowCount = orig.rowCount
	tab.OriginalColCount = orig.colCount

	return nil
}

const ForbiddenValue = -1

type CompressorRowDisplacementTable struct {
	OriginalRowCount int
	OriginalColCount int
	EmptyValue       int
	Entries          []int
	Bounds           []int
	RowDisplacement  []int
}

func NewCompressorRowDisplacementTable(emptyValue int) *CompressorRowDisplacementTable {
	return &CompressorRowDisplacementTable{
		EmptyValue: emptyValue,
	}
}

func (tab *CompressorRowDisplacementTable) Lookup(row int, col int) (int, error) {
	if row < 0 || row >= tab.OriginalRowCount || col < 0 || col >= tab.OriginalColCount {
		return tab.EmptyValue, fmt.Errorf("indexes are out of range: [%v, %v]", row, col)
	}
	d := tab.RowDisplacement[row]
	if tab.Bounds[d+col] != row {
		return tab.EmptyValue, nil
	}
	return tab.Entries[d+col], nil
}

func (tab *CompressorRowDisplacementTable) OriginalTableSize() (int, int) {
	return tab.OriginalRowCount, tab.OriginalColCount
}

type rowInfo struct {
	rowNum        int
	nonEmptyCount int
	nonEmptyCol   []int
}

func (tab *CompressorRowDisplacementTable) Compress(orig *OriginalTable) error {
	rowInfo := make([]rowInfo, orig.rowCount)
	{
		row := 0
		col := 0
		rowInfo[0].rowNum = 0
		for _, v := range orig.entries {
			if col == orig.colCount {
				row++
				col = 0
				rowInfo[row].rowNum = row
			}
			if v != tab.EmptyValue {
				rowInfo[row].nonEmptyCount++
				rowInfo[row].nonEmptyCol = append(rowInfo[row].nonEmptyCol, col)
			}
			col++
		}

		sort.SliceStable(rowInfo, func(i int, j int) bool {
			return rowInfo[i].nonEmptyCount > rowInfo[j].nonEmptyCount
		})
	}

	origEntriesLen := len(orig.entries)
	entries := make([]int, origEntriesLen)
	bounds := make([]int, origEntriesLen)
	resultBottom := orig.colCount
	rowDisplacement := make([]int, orig.rowCount)
	{
		for i := 0; i < origEntriesLen; i++ {
			entries[i] = tab.EmptyValue
			bounds[i] = ForbiddenValue
		}

		nextRowDisplacement := 0
		for _, rInfo := range rowInfo {
			if rInfo.nonEmptyCount <= 0 {
				continue
			}

			for {
				isOverlapped := false
				for _, col := range rInfo.nonEmptyCol {
					if entries[nextRowDisplacement+col] == tab.EmptyValue {
						continue
					}
					nextRowDisplacement++
					isOverlapped = true
					break
				}
				if isOverlapped {
					continue
				}

				rowDisplacement[rInfo.rowNum] = nextRowDisplacement
				for _, col := range rInfo.nonEmptyCol {
					entries[nextRowDisplacement+col] = orig.entries[(rInfo.rowNum*orig.colCount)+col]
					bounds[nextRowDisplacement+col] = rInfo.rowNum
				}
				resultBottom = nextRowDisplacement + orig.colCount
				nextRowDisplacement++
				break
			}
		}
	}

	tab.OriginalRowCount = orig.rowCount
	tab.OriginalColCount = orig.colCount
	tab.Entries = entries[:resultBottom]
	tab.Bounds = bounds[:resultBottom]
	tab.RowDisplacement = rowDisplacement

	return nil
}



func Main() {
}

var rep = strings.NewReplacer(
	`.`, `\.`,
	`*`, `\*`,
	`+`, `\+`,
	`?`, `\?`,
	`|`, `\|`,
	`(`, `\(`,
	`)`, `\)`,
	`[`, `\[`,
	`\`, `\\`,
)

// EscapePattern escapes the special characters.
// For example, EscapePattern(`+`) returns `\+`.
func EscapePattern(s string) string {
	return rep.Replace(s)
}

// LexKindID represents an ID of a lexical kind and is unique across all modes.
type LexKindID int

const (
	LexKindIDNil = LexKindID(0)
	LexKindIDMin = LexKindID(1)
)

func (id LexKindID) Int() int {
	return int(id)
}

// LexModeKindID represents an ID of a lexical kind and is unique within a mode.
// Use LexKindID to identify a kind across all modes uniquely.
type LexModeKindID int

const (
	LexModeKindIDNil = LexModeKindID(0)
	LexModeKindIDMin = LexModeKindID(1)
)

func (id LexModeKindID) Int() int {
	return int(id)
}

// LexKindName represents a name of a lexical kind.
type LexKindName string

const LexKindNameNil = LexKindName("")

func (k LexKindName) String() string {
	return string(k)
}

func (k LexKindName) validate() error {
	err := validateIdentifier(k.String())
	if err != nil {
		return fmt.Errorf("invalid kind name: %v", err)
	}
	return nil
}

// LexPattern represents a pattern of a lexeme.
// The pattern is written in regular expression.
type LexPattern string

func (p LexPattern) validate() error {
	if p == "" {
		return fmt.Errorf("pattern doesn't allow to be the empty string")
	}
	return nil
}

// LexModeID represents an ID of a lex mode.
type LexModeID int

const (
	LexModeIDNil     = LexModeID(0)
	LexModeIDDefault = LexModeID(1)
)

func (n LexModeID) String() string {
	return strconv.Itoa(int(n))
}

func (n LexModeID) Int() int {
	return int(n)
}

func (n LexModeID) IsNil() bool {
	return n == LexModeIDNil
}

// LexModeName represents a name of a lex mode.
type LexModeName string

const (
	LexModeNameNil     = LexModeName("")
	LexModeNameDefault = LexModeName("default")
)

func (m LexModeName) String() string {
	return string(m)
}

func (m LexModeName) validate() error {
	err := validateIdentifier(m.String())
	if err != nil {
		return fmt.Errorf("invalid mode name: %v", err)
	}
	return nil
}

const idPattern = `^[a-z](_?[0-9a-z]+)*$`

var idRE = regexp.MustCompile(idPattern)

func validateIdentifier(id string) error {
	if id == "" {
		return fmt.Errorf("identifier doesn't allow to be the empty string")
	}
	if !idRE.MatchString(id) {
		return fmt.Errorf("identifier must be %v", idPattern)
	}
	return nil
}

func SnakeCaseToUpperCamelCase(snake string) string {
	elems := strings.Split(snake, "_")
	for i, e := range elems {
		if len(e) == 0 {
			continue
		}
		elems[i] = strings.ToUpper(string(e[0])) + e[1:]
	}

	return strings.Join(elems, "")
}

type LexEntry struct {
	Kind     LexKindName   `json:"kind"`
	Pattern  LexPattern    `json:"pattern"`
	Modes    []LexModeName `json:"modes"`
	Push     LexModeName   `json:"push"`
	Pop      bool          `json:"pop"`
	Fragment bool          `json:"fragment"`
}

func (e *LexEntry) validate() error {
	err := e.Kind.validate()
	if err != nil {
		return err
	}
	err = e.Pattern.validate()
	if err != nil {
		return err
	}
	if len(e.Modes) > 0 {
		for _, mode := range e.Modes {
			err = mode.validate()
			if err != nil {
				return err
			}
		}
	}
	return nil
}

type LexSpec struct {
	Name    string      `json:"name"`
	Entries []*LexEntry `json:"entries"`
}

func (s *LexSpec) Validate() error {
	err := validateIdentifier(s.Name)
	if err != nil {
		return fmt.Errorf("invalid specification name: %v", err)
	}

	if len(s.Entries) <= 0 {
		return fmt.Errorf("the lexical specification must have at least one entry")
	}
	{
		var errs []error
		for i, e := range s.Entries {
			err := e.validate()
			if err != nil {
				errs = append(errs, fmt.Errorf("entry #%v: %w", i+1, err))
			}
		}
		if len(errs) > 0 {
			var b strings.Builder
			fmt.Fprintf(&b, "%v", errs[0])
			for _, err := range errs[1:] {
				fmt.Fprintf(&b, "\n%v", err)
			}
			return fmt.Errorf(b.String())
		}
	}
	{
		ks := map[string]struct{}{}
		fks := map[string]struct{}{}
		for _, e := range s.Entries {
			// Allow duplicate names between fragments and non-fragments.
			if e.Fragment {
				if _, exist := fks[e.Kind.String()]; exist {
					return fmt.Errorf("kinds `%v` are duplicates", e.Kind)
				}
				fks[e.Kind.String()] = struct{}{}
			} else {
				if _, exist := ks[e.Kind.String()]; exist {
					return fmt.Errorf("kinds `%v` are duplicates", e.Kind)
				}
				ks[e.Kind.String()] = struct{}{}
			}
		}
	}
	{
		kinds := []string{}
		modes := []string{
			LexModeNameDefault.String(), // This is a predefined mode.
		}
		for _, e := range s.Entries {
			if e.Fragment {
				continue
			}

			kinds = append(kinds, e.Kind.String())

			for _, m := range e.Modes {
				modes = append(modes, m.String())
			}
		}

		kindErrs := findSpellingInconsistenciesErrors(kinds, nil)
		modeErrs := findSpellingInconsistenciesErrors(modes, func(ids []string) error {
			if SnakeCaseToUpperCamelCase(ids[0]) == SnakeCaseToUpperCamelCase(LexModeNameDefault.String()) {
				var b strings.Builder
				fmt.Fprintf(&b, "%+v", ids[0])
				for _, id := range ids[1:] {
					fmt.Fprintf(&b, ", %+v", id)
				}
				return fmt.Errorf("these identifiers are treated as the same. please use the same spelling as predefined '%v': %v", LexModeNameDefault, b.String())
			}
			return nil
		})
		errs := append(kindErrs, modeErrs...)
		if len(errs) > 0 {
			var b strings.Builder
			fmt.Fprintf(&b, "%v", errs[0])
			for _, err := range errs[1:] {
				fmt.Fprintf(&b, "\n%v", err)
			}
			return fmt.Errorf(b.String())
		}
	}

	return nil
}

func findSpellingInconsistenciesErrors(ids []string, hook func(ids []string) error) []error {
	duplicated := FindSpellingInconsistencies(ids)
	if len(duplicated) == 0 {
		return nil
	}

	var errs []error
	for _, dup := range duplicated {
		if hook != nil {
			err := hook(dup)
			if err != nil {
				errs = append(errs, err)
				continue
			}
		}

		var b strings.Builder
		fmt.Fprintf(&b, "%+v", dup[0])
		for _, id := range dup[1:] {
			fmt.Fprintf(&b, ", %+v", id)
		}
		err := fmt.Errorf("these identifiers are treated as the same. please use the same spelling: %v", b.String())
		errs = append(errs, err)
	}

	return errs
}

// FindSpellingInconsistencies finds spelling inconsistencies in identifiers. The identifiers are considered to be the same
// if they are spelled the same when expressed in UpperCamelCase. For example, `left_paren` and `LeftParen` are spelled the same
// in UpperCamelCase. Thus they are considere to be spelling inconsistency.
func FindSpellingInconsistencies(ids []string) [][]string {
	m := map[string][]string{}
	for _, id := range removeDuplicates(ids) {
		c := SnakeCaseToUpperCamelCase(id)
		m[c] = append(m[c], id)
	}

	var duplicated [][]string
	for _, camels := range m {
		if len(camels) == 1 {
			continue
		}
		duplicated = append(duplicated, camels)
	}

	for _, dup := range duplicated {
		sort.Slice(dup, func(i, j int) bool {
			return dup[i] < dup[j]
		})
	}
	sort.Slice(duplicated, func(i, j int) bool {
		return duplicated[i][0] < duplicated[j][0]
	})

	return duplicated
}

func removeDuplicates(s []string) []string {
	m := map[string]struct{}{}
	for _, v := range s {
		m[v] = struct{}{}
	}

	var unique []string
	for v := range m {
		unique = append(unique, v)
	}

	return unique
}

// StateID represents an ID of a state of a transition table.
type StateID int

const (
	// StateIDNil represents an empty entry of a transition table.
	// When the driver reads this value, it raises an error meaning lexical analysis failed.
	StateIDNil = StateID(0)

	// StateIDMin is the minimum value of the state ID. All valid state IDs are represented as
	// sequential numbers starting from this value.
	StateIDMin = StateID(1)
)

func (id StateID) Int() int {
	return int(id)
}

type SpecRowDisplacementTable struct {
	OriginalRowCount int       `json:"original_row_count"`
	OriginalColCount int       `json:"original_col_count"`
	EmptyValue       StateID   `json:"empty_value"`
	Entries          []StateID `json:"entries"`
	Bounds           []int     `json:"bounds"`
	RowDisplacement  []int     `json:"row_displacement"`
}

type SpecUniqueEntriesTable struct {
	UniqueEntries             *SpecRowDisplacementTable `json:"unique_entries,omitempty"`
	UncompressedUniqueEntries []StateID             `json:"uncompressed_unique_entries,omitempty"`
	RowNums                   []int                 `json:"row_nums"`
	OriginalRowCount          int                   `json:"original_row_count"`
	OriginalColCount          int                   `json:"original_col_count"`
	EmptyValue                int                   `json:"empty_value"`
}

type TransitionTable struct {
	InitialStateID         StateID             `json:"initial_state_id"`
	AcceptingStates        []LexModeKindID     `json:"accepting_states"`
	RowCount               int                 `json:"row_count"`
	ColCount               int                 `json:"col_count"`
	Transition             *SpecUniqueEntriesTable `json:"transition,omitempty"`
	UncompressedTransition []StateID           `json:"uncompressed_transition,omitempty"`
}

type CompiledLexModeSpec struct {
	KindNames []LexKindName    `json:"kind_names"`
	Push      []LexModeID      `json:"push"`
	Pop       []int            `json:"pop"`
	DFA       *TransitionTable `json:"dfa"`
}

type CompiledLexSpec struct {
	Name             string                 `json:"name"`
	InitialModeID    LexModeID              `json:"initial_mode_id"`
	ModeNames        []LexModeName          `json:"mode_names"`
	KindNames        []LexKindName          `json:"kind_names"`
	KindIDs          [][]LexKindID          `json:"kind_ids"`
	CompressionLevel int                    `json:"compression_level"`
	Specs            []*CompiledLexModeSpec `json:"specs"`
}