/**
 * This file is part of the Fun programming language.
 * https://fun-lang.xyz/
 *
 * Copyright 2025 Johannes Findeisen <you@hanez.org>
 * Licensed under the terms of the Apache-2.0 license.
 * https://opensource.org/license/apache-2-0
 */

#ifndef FUN_VM_H
#define FUN_VM_H

#include "bytecode.h"

#define MAX_FRAMES 128
#define MAX_FRAME_LOCALS 64
#define MAX_GLOBALS 128
#define OUTPUT_SIZE 1024
#define STACK_SIZE 1024

static const char *opcode_names[] = {
    "NOP","LOAD_CONST","LOAD_LOCAL","STORE_LOCAL",
    "LOAD_GLOBAL","STORE_GLOBAL","ADD","SUB","MUL","DIV",
    "LT","LTE","GT","GTE","EQ","NEQ","POP","JUMP",
    "JUMP_IF_FALSE","CALL","RETURN","PRINT","ECHO","HALT",
    "LINE",
    "MOD","AND","OR","NOT","DUP","SWAP",
    "MAKE_ARRAY","INDEX_GET","INDEX_SET",
    "LEN","PUSH","APOP","SET","INSERT","REMOVE","SLICE",
    "TO_NUMBER","TO_STRING","CAST","TYPEOF",
    "SPLIT","JOIN","SUBSTR","FIND",
    "REGEX_MATCH","REGEX_SEARCH","REGEX_REPLACE",
    "CONTAINS","INDEX_OF","CLEAR",
    "ENUMERATE","ZIP",
    "MIN","MAX","CLAMP","ABS","POW","RANDOM_SEED","RANDOM_INT",
    "MAKE_MAP","KEYS","VALUES","HAS_KEY",
    "READ_FILE","WRITE_FILE","ENV","INPUT_LINE","PROC_RUN","PROC_SYSTEM",
    "TIME_NOW_MS","CLOCK_MONO_MS","DATE_FORMAT",
    "THREAD_SPAWN","THREAD_JOIN","SLEEP_MS",
    "RANDOM_NUMBER",
    "BAND","BOR","BXOR","BNOT","SHL","SHR","ROTL","ROTR",
    "JSON_PARSE","JSON_STRINGIFY","JSON_FROM_FILE","JSON_TO_FILE",
    "CURL_GET","CURL_POST","CURL_DOWNLOAD",
    "SQLITE_OPEN","SQLITE_CLOSE","SQLITE_EXEC","SQLITE_QUERY",
    "LIBSQL_OPEN","LIBSQL_CLOSE","LIBSQL_EXEC","LIBSQL_QUERY",
    "PCSC_ESTABLISH","PCSC_RELEASE","PCSC_LIST_READERS","PCSC_CONNECT","PCSC_DISCONNECT","PCSC_TRANSMIT",
    "PCRE2_TEST","PCRE2_MATCH","PCRE2_FINDALL",
    "INI_LOAD","INI_FREE","INI_GET_STRING","INI_GET_INT","INI_GET_DOUBLE","INI_GET_BOOL","INI_SET","INI_UNSET","INI_SAVE",
    "XML_PARSE","XML_ROOT","XML_NAME","XML_TEXT",
    "SOCK_TCP_LISTEN","SOCK_TCP_ACCEPT","SOCK_TCP_CONNECT","SOCK_SEND","SOCK_RECV","SOCK_CLOSE","SOCK_UNIX_LISTEN","SOCK_UNIX_CONNECT",
    "EXIT",
    "OS_LIST_DIR",
    "TK_BIND",
    "SERIAL_OPEN","SERIAL_CONFIG","SERIAL_SEND","SERIAL_RECV","SERIAL_CLOSE",
    "TK_EVAL","TK_RESULT","TK_LOOP","TK_WM_TITLE","TK_LABEL","TK_BUTTON","TK_PACK",
    "TRY_PUSH","TRY_POP","THROW",
    /* Notcurses TUI (optional) */
    "NC_INIT","NC_SHUTDOWN","NC_CLEAR","NC_DRAW_TEXT","NC_GETCH"
};

typedef struct {
    Bytecode *fn;
    int ip;
    Value locals[MAX_FRAME_LOCALS];
    /* exception handling (per-frame) */
    int try_stack[16];
    int try_sp; /* -1 when empty */
} Frame;

struct VM {
    Value stack[STACK_SIZE];
    int sp;

    Frame frames[MAX_FRAMES];
    int fp; // frame pointer, -1 when no frame

    Value globals[MAX_GLOBALS];

    Value output[OUTPUT_SIZE]; // store printed values
    int output_count;
    int output_is_partial[OUTPUT_SIZE]; // 1 when the corresponding output entry should not end with newline (echo)

    long long instr_count; // executed instructions in the last vm_run

    int current_line; // last executed source line (debug)

    int exit_code; // process exit code set by OP_EXIT

    int trace_enabled; // when non-zero, print executed ops and stack
    int repl_on_error; // when non-zero, enter REPL on runtime error (preserve stack)
    int (*on_error_repl)(struct VM *vm); // optional hook to run REPL on error

    /* --- Debugger state --- */
    int debug_step_mode;        // 0 none, 1 step, 2 next, 3 finish
    int debug_step_target_fp;   // target frame pointer for next/finish
    long long debug_step_start_ic; // instruction count snapshot when step/next requested
    int debug_stop_requested;   // force a pause at loop top

    struct {
        char *file;             // strdup'ed file path
        int line;               // 1-based line
        int active;             // 1 if active
    } breakpoints[64];
    int break_count;            // number of active breakpoints
};

typedef struct VM VM;

// initialize VM (zero state)
void vm_init(VM *vm);

// helper function to clear the output
void vm_clear_output(VM *vm);
void vm_print_output(VM *vm);
void vm_free(VM *vm);

// reset VM to initial state (free globals/locals/output; keep VM object)
void vm_reset(VM *vm);

// print non-nil globals (index and value) to stdout
void vm_dump_globals(VM *vm);
// run entry Bytecode (pushes first frame)
void vm_run(VM *vm, Bytecode *entry);

/* Raise a runtime error that respects try/catch/finally.
 * If a try handler is active in the current frame, control jumps to it
 * with an error string pushed on the stack. Otherwise, prints the error
 * (annotated with location) and terminates execution. */
void vm_raise_error(VM *vm, const char *msg);

/* --- Debugger API --- */
void vm_debug_reset(VM *vm);
int  vm_debug_add_breakpoint(VM *vm, const char *file, int line); // returns id >=0 or -1
int  vm_debug_delete_breakpoint(VM *vm, int id);                   // returns 1 on success
void vm_debug_clear_breakpoints(VM *vm);
void vm_debug_list_breakpoints(VM *vm);
void vm_debug_request_step(VM *vm);
void vm_debug_request_next(VM *vm);
void vm_debug_request_finish(VM *vm);
void vm_debug_request_continue(VM *vm);

static inline int opcode_is_valid(int op) {
    return op >= OP_NOP && op <= OP_NC_GETCH;  // all current opcodes (including optional NC_*)
}

#endif