// values.h -- DVX BASIC value representation and string heap
//
// Tagged union value type for the VM's evaluation stack, variables,
// and array elements. Strings are reference-counted for automatic
// memory management without a garbage collector.
//
// Embeddable: no DVX dependencies, pure C.

#ifndef DVXBASIC_VALUES_H
#define DVXBASIC_VALUES_H

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

// ============================================================
// Reference-counted string
// ============================================================

typedef struct {
    int32_t  refCount;
    int32_t  len;
    int32_t  cap;      // allocated capacity (>= len + 1)
    char     data[];   // flexible array member, null-terminated
} BasStringT;

// Allocate a new string from a C string. refCount starts at 1.
BasStringT *basStringNew(const char *text, int32_t len);

// Allocate an empty string with a given capacity.
BasStringT *basStringAlloc(int32_t cap);

// Increment reference count.
BasStringT *basStringRef(BasStringT *s);

// Decrement reference count. Frees if count reaches zero.
void basStringUnref(BasStringT *s);

// Concatenate two strings. Returns a new string (refCount 1).
BasStringT *basStringConcat(const BasStringT *a, const BasStringT *b);

// Substring. Returns a new string (refCount 1).
BasStringT *basStringSub(const BasStringT *s, int32_t start, int32_t len);

// Compare two strings. Returns <0, 0, >0 like strcmp.
int32_t basStringCompare(const BasStringT *a, const BasStringT *b);

// Compare two strings case-insensitively. Returns <0, 0, >0.
int32_t basStringCompareCI(const BasStringT *a, const BasStringT *b);

// The empty string singleton (never freed).
extern BasStringT *basEmptyString;

// Initialize/shutdown the string system.
void basStringSystemInit(void);
void basStringSystemShutdown(void);

// ============================================================
// Forward declarations
// ============================================================

typedef struct BasValueTag BasValueT;

// ============================================================
// Reference-counted array
// ============================================================

#define BAS_ARRAY_MAX_DIMS 8

typedef struct {
    int32_t    refCount;
    uint8_t    elementType;              // BAS_TYPE_*
    int32_t    dims;                     // number of dimensions
    int32_t    lbound[BAS_ARRAY_MAX_DIMS]; // lower bound per dimension
    int32_t    ubound[BAS_ARRAY_MAX_DIMS]; // upper bound per dimension
    int32_t    totalElements;
    BasValueT *elements;                 // flat array of values
} BasArrayT;

// Allocate a new array. refCount starts at 1.
BasArrayT *basArrayNew(int32_t dims, int32_t *lbounds, int32_t *ubounds, uint8_t elementType);

// Free all elements and release the array.
void basArrayFree(BasArrayT *arr);

// Increment reference count.
BasArrayT *basArrayRef(BasArrayT *arr);

// Decrement reference count. Frees if count reaches zero.
void basArrayUnref(BasArrayT *arr);

// Compute flat index from multi-dimensional indices. Returns -1 if out of bounds.
int32_t basArrayIndex(BasArrayT *arr, int32_t *indices, int32_t ndims);

// ============================================================
// Reference-counted user-defined type instance
// ============================================================

typedef struct {
    int32_t    refCount;
    int32_t    typeId;       // index into type definition table
    int32_t    fieldCount;
    BasValueT *fields;       // array of field values
} BasUdtT;

// Allocate a new UDT instance. refCount starts at 1.
BasUdtT *basUdtNew(int32_t typeId, int32_t fieldCount);

// Free all fields and release the UDT.
void basUdtFree(BasUdtT *udt);

// Increment reference count.
BasUdtT *basUdtRef(BasUdtT *udt);

// Decrement reference count. Frees if count reaches zero.
void basUdtUnref(BasUdtT *udt);

// ============================================================
// Tagged value
// ============================================================

struct BasValueTag {
    uint8_t type;  // BAS_TYPE_*
    union {
        int16_t     intVal;    // BAS_TYPE_INTEGER
        int32_t     longVal;   // BAS_TYPE_LONG
        float       sngVal;    // BAS_TYPE_SINGLE
        double      dblVal;    // BAS_TYPE_DOUBLE
        BasStringT *strVal;    // BAS_TYPE_STRING (ref-counted)
        int16_t     boolVal;   // BAS_TYPE_BOOLEAN (True=-1, False=0)
        BasArrayT  *arrVal;    // BAS_TYPE_ARRAY (ref-counted)
        BasUdtT    *udtVal;    // BAS_TYPE_UDT (ref-counted)
    };
};

// Create values
BasValueT basValInteger(int16_t v);
BasValueT basValLong(int32_t v);
BasValueT basValSingle(float v);
BasValueT basValDouble(double v);
BasValueT basValString(BasStringT *s);
BasValueT basValStringFromC(const char *text);
BasValueT basValBool(bool v);

// Copy a value (increments string refcount if applicable).
BasValueT basValCopy(BasValueT v);

// Release a value (decrements string refcount if applicable).
void basValRelease(BasValueT *v);

// Convert a value to a specific type. Returns the converted value.
// The original is NOT released -- caller manages lifetime.
BasValueT basValToInteger(BasValueT v);
BasValueT basValToLong(BasValueT v);
BasValueT basValToSingle(BasValueT v);
BasValueT basValToDouble(BasValueT v);
BasValueT basValToString(BasValueT v);
BasValueT basValToBool(BasValueT v);

// Get the numeric value as a double (for mixed-type arithmetic).
double basValToNumber(BasValueT v);

// Get the string representation. Returns a new ref-counted string.
BasStringT *basValFormatString(BasValueT v);

// Check if a value is truthy (non-zero number, non-empty string).
bool basValIsTruthy(BasValueT v);

// Compare two values. Returns -1, 0, or 1.
// Numeric types are compared numerically. Strings lexicographically.
int32_t basValCompare(BasValueT a, BasValueT b);

// Compare two values case-insensitively (for OPTION COMPARE TEXT).
int32_t basValCompareCI(BasValueT a, BasValueT b);

// Determine the common type for a binary operation (type promotion).
// Integer + Single -> Single, etc.
uint8_t basValPromoteType(uint8_t a, uint8_t b);

#endif // DVXBASIC_VALUES_H