// lexer.h -- DVX BASIC lexer (tokenizer)
//
// Converts BASIC source text into a stream of tokens. Case-insensitive
// for keywords. Handles line continuations (_), comments (' and REM),
// type suffixes (%, &, !, #, $), and string literals.
//
// Embeddable: no DVX dependencies, pure C.

#ifndef DVXBASIC_LEXER_H
#define DVXBASIC_LEXER_H

#include <stdint.h>
#include <stdbool.h>

// ============================================================
// Token types
// ============================================================

typedef enum {
    // Literals
    TOK_INT_LIT,           // integer literal (123, &HFF)
    TOK_LONG_LIT,          // long literal (123&)
    TOK_FLOAT_LIT,         // float literal (3.14, 1.5E10)
    TOK_STRING_LIT,        // "string literal"

    // Identifiers and symbols
    TOK_IDENT,             // variable/function name
    TOK_DOT,               // .
    TOK_COMMA,             // ,
    TOK_SEMICOLON,         // ;
    TOK_COLON,             // :
    TOK_LPAREN,            // (
    TOK_RPAREN,            // )
    TOK_HASH,              // # (file channel)

    // Operators
    TOK_PLUS,              // +
    TOK_MINUS,             // -
    TOK_STAR,              // *
    TOK_SLASH,             // /
    TOK_BACKSLASH,         // \ (integer divide)
    TOK_CARET,             // ^
    TOK_AMPERSAND,         // & (string concat or hex prefix)
    TOK_EQ,                // =
    TOK_NE,                // <>
    TOK_LT,                // <
    TOK_GT,                // >
    TOK_LE,                // <=
    TOK_GE,                // >=

    // Type suffixes (attached to identifier)
    TOK_SUFFIX_INT,        // %
    TOK_SUFFIX_LONG,       // &
    TOK_SUFFIX_SINGLE,     // !
    TOK_SUFFIX_DOUBLE,     // #
    TOK_SUFFIX_STRING,     // $

    // Keywords
    TOK_AND,
    TOK_APP,
    TOK_AS,
    TOK_BASE,
    TOK_BOOLEAN,
    TOK_BYVAL,
    TOK_CALL,
    TOK_CASE,
    TOK_CLOSE,
    TOK_CONST,
    TOK_DATA,
    TOK_DECLARE,
    TOK_DEF,
    TOK_DEFDBL,
    TOK_DEFINT,
    TOK_DEFLNG,
    TOK_DEFSNG,
    TOK_DEFSTR,
    TOK_DIM,
    TOK_DO,
    TOK_DOEVENTS,
    TOK_DOUBLE,
    TOK_ELSE,
    TOK_ELSEIF,
    TOK_END,
    TOK_EOF_KW,            // EOF (keyword, not end-of-file)
    TOK_EQV,
    TOK_ERASE,
    TOK_ERR,
    TOK_ERROR_KW,
    TOK_EXPLICIT,
    TOK_EXIT,
    TOK_FALSE_KW,
    TOK_FOR,
    TOK_FUNCTION,
    TOK_GET,
    TOK_GOSUB,
    TOK_GOTO,
    TOK_HIDE,
    TOK_IF,
    TOK_IMP,
    TOK_INPUT,
    TOK_INTEGER,
    TOK_IS,
    TOK_LBOUND,
    TOK_LET,
    TOK_LINE,
    TOK_LOAD,
    TOK_LONG,
    TOK_LOOP,
    TOK_ME,
    TOK_MOD,
    TOK_MSGBOX,
    TOK_NEXT,
    TOK_NOT,
    TOK_ON,
    TOK_OPEN,
    TOK_OPTION,
    TOK_OR,
    TOK_OUTPUT,
    TOK_PRESERVE,
    TOK_PRINT,
    TOK_PUT,
    TOK_RANDOMIZE,
    TOK_READ,
    TOK_REDIM,
    TOK_REM,
    TOK_RESTORE,
    TOK_RESUME,
    TOK_RETURN,
    TOK_SEEK,
    TOK_SELECT,
    TOK_SET,
    TOK_SHARED,
    TOK_SHELL,
    TOK_SHOW,
    TOK_SINGLE,
    TOK_SLEEP,
    TOK_INIREAD,
    TOK_INIWRITE,
    TOK_SQLCLOSE,
    TOK_SQLEOF,
    TOK_SQLERROR,
    TOK_SQLEXEC,
    TOK_SQLFIELD,       // SQLField$(rs, col) or SQLField$(rs, "name")
    TOK_SQLFIELDCOUNT,
    TOK_SQLFIELDINT,
    TOK_SQLFIELDDBL,
    TOK_SQLFREERESULT,
    TOK_SQLNEXT,
    TOK_SQLOPEN,
    TOK_SQLQUERY,
    TOK_SQLAFFECTED,
    TOK_STATIC,
    TOK_STEP,
    TOK_STRING_KW,
    TOK_SUB,
    TOK_SWAP,
    TOK_THEN,
    TOK_TIMER,
    TOK_TO,
    TOK_TRUE_KW,
    TOK_TYPE,
    TOK_UBOUND,
    TOK_UNLOAD,
    TOK_UNTIL,
    TOK_WEND,
    TOK_WHILE,
    TOK_WITH,
    TOK_WRITE,
    TOK_XOR,

    // File modes
    TOK_APPEND,
    TOK_BINARY,
    TOK_RANDOM,

    // Special
    TOK_NEWLINE,           // end of logical line
    TOK_EOF,               // end of source
    TOK_ERROR              // lexer error
} BasTokenTypeE;

// ============================================================
// Token
// ============================================================

#define BAS_MAX_TOKEN_LEN 256

typedef struct {
    BasTokenTypeE type;
    int32_t       line;    // 1-based source line number
    int32_t       col;     // 1-based column number

    // Value (depends on type)
    union {
        int32_t   intVal;
        int64_t   longVal;
        float     fltVal;
        double    dblVal;
    };

    char text[BAS_MAX_TOKEN_LEN];  // raw text of the token
    int32_t textLen;
} BasTokenT;

// ============================================================
// Lexer state
// ============================================================

typedef struct {
    const char *source;    // source text (not owned)
    int32_t     sourceLen;
    int32_t     pos;       // current position in source
    int32_t     line;      // current line (1-based)
    int32_t     col;       // current column (1-based)
    BasTokenT   token;     // current token
    char        error[256];
} BasLexerT;

// ============================================================
// API
// ============================================================

// Initialize lexer with source text. The source must remain valid
// for the lifetime of the lexer.
void basLexerInit(BasLexerT *lex, const char *source, int32_t sourceLen);

// Advance to the next token. Returns the token type.
// The token is available in lex->token.
BasTokenTypeE basLexerNext(BasLexerT *lex);

// Peek at the current token type without advancing.
BasTokenTypeE basLexerPeek(const BasLexerT *lex);

// Return human-readable name for a token type.
const char *basTokenName(BasTokenTypeE type);

#endif // DVXBASIC_LEXER_H