// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// Token definitions for the Five (Harbour-compatible) language.
// Pattern follows tsgo's Kind+Precedence approach
// (ref/typescript-go/internal/ast/kind.go, precedence.go).
package token

import "strconv"

// Kind represents a token type. Using int16 following tsgo pattern.
type Kind int16

const (
	// Special
	ILLEGAL Kind = iota
	EOF
	NEWLINE // statement terminator

	// Literals
	INT       // 42
	LONG      // 42L or large integer
	DOUBLE    // 3.14
	STRING    // "hello" or 'hello'
	DATE_LIT  // 0d20260327 or CTOD("20260327")
	TRUE      // .T.
	FALSE     // .F.
	NIL_LIT   // NIL

	// Identifiers
	IDENT // variable/function name

	// Operators
	PLUS       // +
	MINUS      // -
	STAR       // *
	SLASH      // /
	PERCENT    // %
	POWER      // ** or ^
	ASSIGN     // :=
	EQ         // = or ==
	EXEQ       // ==
	NEQ        // != or <> or #
	LT         // <
	GT         // >
	LTE        // <=
	GTE        // >=
	DOLLAR     // $ (string containment)
	AMPERSAND  // & (macro)
	AT         // @ (pass by ref)
	ARROW      // -> (alias field access)
	DBLARROW   // => (hash pair)
	COLONCOLON // :: (self access)
	COLON      // : (send message)
	DOT        // .
	INC        // ++ (postfix)
	DEC        // -- (postfix)
	PLUSEQ     // +=
	MINUSEQ    // -=
	STAREQ     // *=
	SLASHEQ    // /=
	PERCENTEQ  // %=
	POWEREQ    // **=

	// Logical operators (keyword-style)
	AND // .AND.
	OR  // .OR.
	NOT // .NOT. or !

	// Delimiters
	LPAREN   // (
	RPAREN   // )
	LBRACKET // [
	RBRACKET // ]
	LBRACE   // {
	RBRACE   // }
	COMMA    // ,
	SEMICOLON // ; (line continuation)
	PIPE     // | (in code blocks {|x| ...})
	QMARK    // ? (QOut shorthand)
	QQMARK   // ?? (QQOut shorthand)

	// Keywords — Declarations
	FUNCTION_KW
	PROCEDURE
	RETURN
	LOCAL
	STATIC
	PRIVATE
	PUBLIC
	FIELD
	MEMVAR
	PARAMETERS
	DECLARE

	// Keywords — Control flow
	IF
	ELSEIF
	ELSE
	ENDIF
	DO
	WHILE
	ENDDO
	FOR
	TO
	STEP
	NEXT
	EACH
	IN
	EXIT
	LOOP
	SWITCH
	CASE
	OTHERWISE
	ENDSWITCH
	ENDCASE
	BEGIN
	SEQUENCE
	RECOVER
	USING
	END

	// Keywords — OOP
	CLASS
	ENDCLASS
	DATA
	METHOD
	INHERIT
	FROM
	CONSTRUCTOR
	DESTRUCTOR
	INLINE_KW
	OPERATOR_KW
	ACCESS
	ASSIGN_KW

	// Keywords — xBase commands
	USE
	ALIAS
	SELECT
	GO
	GOTO
	TOP
	BOTTOM
	SKIP_KW
	SEEK
	SOFTSEEK
	REPLACE
	WITH
	APPEND
	BLANK
	DELETE_KW
	RECALL
	PACK
	ZAP
	INDEX
	ON
	UNIQUE
	DESCENDING
	ASCENDING
	SET
	FILTER
	RELATION
	INTO
	ORDER

	// Keywords — New Five extensions
	IMPORT
	GO_KW       // GO (goroutine)
	CHANNEL
	SEND_KW
	RECEIVE
	WAITGROUP
	TYPE_KW     // TYPE ... END TYPE
	AS
	DEFER_KW    // DEFER expr (cleanup on function exit)
	CONST_KW    // CONST ... END CONST (enum block)
	QUESTION_COLON // ?: nil-safe send
	WATCH_KW    // WATCH ... CASE ... ENDWATCH (channel select)
	ASYNC_KW    // ASYNC expr (launch async)
	AWAIT_KW    // AWAIT expr (wait for result)
	PARALLEL_KW // PARALLEL FOR (parallel loop)
	ARROW_LEFT  // <- (channel receive)
	TIMEOUT_KW  // WITH TIMEOUT n
	SPAWN_KW    // SPAWN { block } (goroutine)

	// Keywords — Preprocessor
	PP_INCLUDE  // #include
	PP_DEFINE   // #define
	PP_UNDEF    // #undef
	PP_IFDEF    // #ifdef
	PP_IFNDEF   // #ifndef
	PP_ELSE     // #else
	PP_ENDIF    // #endif
	PP_COMMAND  // #command
	PP_TRANSLATE // #translate
	PP_PRAGMA   // #pragma

	// Internal
	_kindEnd
)

// Token represents a single lexical token.
type Token struct {
	Kind    Kind
	Literal string // raw text
	Pos     Position
}

// Position in source file.
type Position struct {
	File   string
	Line   int
	Col    int
	Offset int // byte offset from start of source
}

func (p Position) String() string {
	if p.File != "" {
		return p.File + ":" + strconv.Itoa(p.Line) + ":" + strconv.Itoa(p.Col)
	}
	return strconv.Itoa(p.Line) + ":" + strconv.Itoa(p.Col)
}

// itoa removed — using strconv.Itoa (fixes math.MinInt overflow bug)

// --- Operator Precedence (tsgo pattern) ---

type Precedence int

const (
	PrecNone       Precedence = iota
	PrecAssign                        // :=, +=, -=, ...
	PrecOr                            // .OR.
	PrecAnd                           // .AND.
	PrecNot                           // .NOT., !
	PrecComparison                    // =, ==, !=, <, >, <=, >=, $
	PrecAddition                      // +, -
	PrecMultiply                      // *, /, %
	PrecPower                         // **, ^
	PrecUnary                         // -, !, .NOT., ++, --
	PrecPostfix                       // ++, --, [], ()
	PrecCall                          // function(), obj:method()
	PrecPrimary                       // literals, identifiers, (expr)
)

// GetBinaryPrecedence returns the precedence of a binary operator token.
// Returns PrecNone if not a binary operator.
// Pattern: tsgo GetBinaryOperatorPrecedence (ref/typescript-go/internal/ast/precedence.go:338)
func GetBinaryPrecedence(kind Kind) Precedence {
	switch kind {
	case ASSIGN, PLUSEQ, MINUSEQ, STAREQ, SLASHEQ, PERCENTEQ, POWEREQ:
		return PrecAssign
	case OR:
		return PrecOr
	case AND:
		return PrecAnd
	case EQ, EXEQ, NEQ, LT, GT, LTE, GTE, DOLLAR:
		return PrecComparison
	case PLUS, MINUS:
		return PrecAddition
	case STAR, SLASH, PERCENT:
		return PrecMultiply
	case POWER:
		return PrecPower
	default:
		return PrecNone
	}
}

// IsRightAssociative returns true for right-to-left operators.
func IsRightAssociative(kind Kind) bool {
	switch kind {
	case POWER, ASSIGN, PLUSEQ, MINUSEQ, STAREQ, SLASHEQ, PERCENTEQ, POWEREQ:
		return true
	default:
		return false
	}
}

// --- Keyword lookup ---

var keywords map[string]Kind

func init() {
	keywords = map[string]Kind{
		"FUNCTION":    FUNCTION_KW,
		"PROCEDURE":   PROCEDURE,
		"RETURN":      RETURN,
		"LOCAL":       LOCAL,
		"STATIC":      STATIC,
		"PRIVATE":     PRIVATE,
		"PUBLIC":      PUBLIC,
		"FIELD":       FIELD,
		"MEMVAR":      MEMVAR,
		"PARAMETERS":  PARAMETERS,
		"DECLARE":     DECLARE,
		"IF":          IF,
		"ELSEIF":      ELSEIF,
		"ELSE":        ELSE,
		"ENDIF":       ENDIF,
		"DO":          DO,
		"WHILE":       WHILE,
		"ENDDO":       ENDDO,
		"FOR":         FOR,
		"TO":          TO,
		"STEP":        STEP,
		"NEXT":        NEXT,
		"EACH":        EACH,
		"IN":          IN,
		"EXIT":        EXIT,
		"LOOP":        LOOP,
		"SWITCH":      SWITCH,
		"CASE":        CASE,
		"OTHERWISE":   OTHERWISE,
		"ENDSWITCH":   ENDSWITCH,
		"ENDCASE":     ENDCASE,
		"BEGIN":       BEGIN,
		"SEQUENCE":    SEQUENCE,
		"RECOVER":     RECOVER,
		"USING":       USING,
		"END":         END,
		"CLASS":       CLASS,
		"ENDCLASS":    ENDCLASS,
		"DATA":        DATA,
		// METHOD: recognized as keyword (used at top level too: METHOD name CLASS classname)
		"METHOD":      METHOD,
		"INHERIT":     INHERIT,
		"FROM":        FROM,
		"CONSTRUCTOR": CONSTRUCTOR,
		"DESTRUCTOR":  DESTRUCTOR,
		"INLINE":      INLINE_KW,
		"OPERATOR":    OPERATOR_KW,
		"ACCESS":      ACCESS,
		"ASSIGN":      ASSIGN_KW,
		"USE":         USE,
		"ALIAS":       ALIAS,
		"SELECT":      SELECT,
		"GO":          GO,
		"GOTO":        GOTO,
		"TOP":         TOP,
		"BOTTOM":      BOTTOM,
		"SKIP":        SKIP_KW,
		"SEEK":        SEEK,
		"SOFTSEEK":    SOFTSEEK,
		"REPLACE":     REPLACE,
		"WITH":        WITH,
		"APPEND":      APPEND,
		"BLANK":       BLANK,
		"DELETE":      DELETE_KW,
		"RECALL":      RECALL,
		"PACK":        PACK,
		"ZAP":         ZAP,
		"INDEX":       INDEX,
		"ON":          ON,
		"UNIQUE":      UNIQUE,
		"DESCENDING":  DESCENDING,
		"ASCENDING":   ASCENDING,
		"SET":         SET,
		"FILTER":      FILTER,
		"RELATION":    RELATION,
		"INTO":        INTO,
		"ORDER":       ORDER,
		"IMPORT":      IMPORT,
		// CHANNEL, SEND, RECEIVE, WAITGROUP — now RTL functions, not keywords
		"TYPE":        TYPE_KW,
		"AS":          AS,
		"DEFER":       DEFER_KW,
		"CONST":       CONST_KW,
		"WATCH":       WATCH_KW,
		"ASYNC":       ASYNC_KW,
		"AWAIT":       AWAIT_KW,
		"PARALLEL":    PARALLEL_KW,
		"TIMEOUT":     TIMEOUT_KW,
		"SPAWN":       SPAWN_KW,
		"LAUNCH":      SPAWN_KW,
		"GOROUTINE":   SPAWN_KW,
		"NIL":         NIL_LIT,
		// Harbour aliases
		"FUNC":     FUNCTION_KW,
		"PROC":     PROCEDURE,
		"RET":      RETURN,
		"ENDW":     ENDDO,    // some Harbour code uses ENDW
	}
}

// LookupKeyword returns the keyword Kind for an identifier, or IDENT.
// Harbour keywords are case-insensitive.
func LookupKeyword(ident string) Kind {
	// Convert to uppercase for case-insensitive lookup
	upper := toUpper(ident)
	if kind, ok := keywords[upper]; ok {
		return kind
	}
	return IDENT
}

// toUpper converts ASCII string to uppercase without allocating for already-upper strings.
func toUpper(s string) string {
	for i := 0; i < len(s); i++ {
		if s[i] >= 'a' && s[i] <= 'z' {
			// Need to allocate
			buf := make([]byte, len(s))
			copy(buf, s[:i])
			for j := i; j < len(s); j++ {
				if s[j] >= 'a' && s[j] <= 'z' {
					buf[j] = s[j] - 32
				} else {
					buf[j] = s[j]
				}
			}
			return string(buf)
		}
	}
	return s // already uppercase
}

// String returns the display name of the token kind.
func (k Kind) String() string {
	if int(k) < len(kindNames) {
		return kindNames[k]
	}
	return "UNKNOWN"
}

var kindNames = [...]string{
	ILLEGAL:     "ILLEGAL",
	EOF:         "EOF",
	NEWLINE:     "NEWLINE",
	INT:         "INT",
	LONG:        "LONG",
	DOUBLE:      "DOUBLE",
	STRING:      "STRING",
	DATE_LIT:    "DATE",
	TRUE:        ".T.",
	FALSE:       ".F.",
	NIL_LIT:     "NIL",
	IDENT:       "IDENT",
	PLUS:        "+",
	MINUS:       "-",
	STAR:        "*",
	SLASH:       "/",
	PERCENT:     "%",
	POWER:       "**",
	ASSIGN:      ":=",
	EQ:          "=",
	EXEQ:        "==",
	NEQ:         "!=",
	LT:          "<",
	GT:          ">",
	LTE:         "<=",
	GTE:         ">=",
	DOLLAR:      "$",
	AMPERSAND:   "&",
	AT:          "@",
	ARROW:       "->",
	DBLARROW:    "=>",
	COLONCOLON:  "::",
	COLON:       ":",
	DOT:         ".",
	INC:         "++",
	DEC:         "--",
	PLUSEQ:      "+=",
	MINUSEQ:     "-=",
	STAREQ:      "*=",
	SLASHEQ:     "/=",
	PERCENTEQ:   "%=",
	POWEREQ:     "**=",
	AND:         ".AND.",
	OR:          ".OR.",
	NOT:         ".NOT.",
	LPAREN:      "(",
	RPAREN:      ")",
	LBRACKET:    "[",
	RBRACKET:    "]",
	LBRACE:      "{",
	RBRACE:      "}",
	COMMA:       ",",
	SEMICOLON:   ";",
	PIPE:        "|",
	FUNCTION_KW: "FUNCTION",
	PROCEDURE:   "PROCEDURE",
	RETURN:      "RETURN",
	LOCAL:       "LOCAL",
	STATIC:      "STATIC",
	IF:          "IF",
	ELSEIF:      "ELSEIF",
	ELSE:        "ELSE",
	ENDIF:       "ENDIF",
	DO:          "DO",
	WHILE:       "WHILE",
	ENDDO:       "ENDDO",
	FOR:         "FOR",
	TO:          "TO",
	STEP:        "STEP",
	NEXT:        "NEXT",
	EACH:        "EACH",
	IN:          "IN",
	EXIT:        "EXIT",
	LOOP:        "LOOP",
	BEGIN:       "BEGIN",
	SEQUENCE:    "SEQUENCE",
	RECOVER:     "RECOVER",
	END:         "END",
	CLASS:       "CLASS",
	ENDCLASS:    "ENDCLASS",
	DATA:        "DATA",
	METHOD:      "METHOD",
	USE:         "USE",
	SEEK:        "SEEK",
	REPLACE:     "REPLACE",
	APPEND:      "APPEND",
	INDEX:       "INDEX",
	SET:         "SET",
	SELECT:      "SELECT",
	IMPORT:      "IMPORT",
	// Missing tokens added for complete String() coverage
	PRIVATE:     "PRIVATE",
	PUBLIC:      "PUBLIC",
	FIELD:       "FIELD",
	MEMVAR:      "MEMVAR",
	PARAMETERS:  "PARAMETERS",
	DECLARE:     "DECLARE",
	SWITCH:      "SWITCH",
	CASE:        "CASE",
	OTHERWISE:   "OTHERWISE",
	ENDSWITCH:   "ENDSWITCH",
	ENDCASE:     "ENDCASE",
	QMARK:       "?",
	QQMARK:      "??",
	BLANK:       "BLANK",
	SKIP_KW:     "SKIP",
	DELETE_KW:   "DELETE",
	RECALL:      "RECALL",
	PACK:        "PACK",
	ZAP:         "ZAP",
	GO:          "GO",
	GOTO:        "GOTO",
	TOP:         "TOP",
	BOTTOM:      "BOTTOM",
	SOFTSEEK:    "SOFTSEEK",
	UNIQUE:      "UNIQUE",
	DESCENDING:  "DESCENDING",
	FROM:        "FROM",
	ON:          "ON",
	WITH:        "WITH",
	ALIAS:       "ALIAS",
	ACCESS:      "ACCESS",
	ASSIGN_KW:   "ASSIGN",
	INHERIT:     "INHERIT",
	INLINE_KW:   "INLINE",
	DESTRUCTOR:  "DESTRUCTOR",
	CONSTRUCTOR: "CONSTRUCTOR",
	OPERATOR_KW: "OPERATOR",
	USING:       "USING",
	TYPE_KW:     "TYPE",
	AS:          "AS",
	GO_KW:       "GO_KW",
	DEFER_KW:    "DEFER",
	CONST_KW:    "CONST",
	WATCH_KW:    "WATCH",
	ASYNC_KW:    "ASYNC",
	AWAIT_KW:    "AWAIT",
	PARALLEL_KW: "PARALLEL",
	TIMEOUT_KW:  "TIMEOUT",
	SPAWN_KW:    "SPAWN",
	ARROW_LEFT:  "<-",
}