#include "forth.h"

// Stack operations
void do_dup(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t v = data_stack[data_sp];
    data_push(v);
}

void do_drop(Word* w) {
    (void)w;
    data_pop();
}

void do_swap(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t a = data_stack[data_sp-1];
    int64_t b = data_stack[data_sp];
    data_stack[data_sp-1] = b;
    data_stack[data_sp] = a;
}

void do_over(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    data_push(data_stack[data_sp-1]);
}

void do_rot(Word* w) {
    (void)w;
    if (data_sp < 2) return;
    int64_t a = data_stack[data_sp-2];
    int64_t b = data_stack[data_sp-1];
    int64_t c = data_stack[data_sp];
    data_stack[data_sp-2] = c;
    data_stack[data_sp-1] = a;
    data_stack[data_sp] = b;
}

void do_minus_rot(Word* w) {
    (void)w;
    if (data_sp < 2) return;
    int64_t a = data_stack[data_sp-2];
    int64_t b = data_stack[data_sp-1];
    int64_t c = data_stack[data_sp];
    data_stack[data_sp-2] = b;
    data_stack[data_sp-1] = c;
    data_stack[data_sp] = a;
}

void do_nip(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    data_stack[data_sp-1] = data_stack[data_sp];
    data_sp--;
}

void do_tuck(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t a = data_stack[data_sp-1];
    int64_t b = data_stack[data_sp];
    data_push(a);
    data_stack[data_sp-2] = b;
}

// Arithmetic
void do_add(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a + b);
}

void do_sub(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a - b);
}

void do_mul(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a * b);
}

void do_div(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    if (b == 0) {
        printf("Division by zero\n");
        data_push(a);
        data_push(b);
        return;
    }
    data_push(a / b);
}

void do_mod(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    if (b == 0) {
        printf("Modulo by zero\n");
        data_push(a);
        data_push(b);
        return;
    }
    data_push(a % b);
}

void do_slash_mod(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    if (b == 0) {
        printf("Modulo by zero\n");
        data_push(a);
        data_push(b);
        return;
    }
    data_push(a / b);
    data_push(a % b);
}

void do_one_plus(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    data_stack[data_sp]++;
}

void do_one_minus(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    data_stack[data_sp]--;
}

void do_two_plus(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    data_stack[data_sp] += 2;
}

void do_two_minus(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    data_stack[data_sp] -= 2;
}

void do_negate(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    data_stack[data_sp] = -data_stack[data_sp];
}

void do_abs(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t v = data_pop();
    data_push(v < 0 ? -v : v);
}

void do_min(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a < b ? a : b);
}

void do_max(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a > b ? a : b);
}

// Logic
void do_and(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a & b);
}

void do_or(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a | b);
}

void do_xor(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a ^ b);
}

void do_invert(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    data_stack[data_sp] = ~data_stack[data_sp];
}

void do_lshift(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a << b);
}

void do_rshift(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push((int64_t)((uint64_t)a >> b));
}

// Comparison
void do_eq(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a == b ? -1 : 0);
}

void do_neq(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a != b ? -1 : 0);
}

void do_lt(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a < b ? -1 : 0);
}

void do_gt(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a > b ? -1 : 0);
}

void do_lte(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a <= b ? -1 : 0);
}

void do_gte(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_pop();
    int64_t a = data_pop();
    data_push(a >= b ? -1 : 0);
}

void do_zero_eq(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t a = data_pop();
    data_push(a == 0 ? -1 : 0);
}

void do_zero_lt(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t a = data_pop();
    data_push(a < 0 ? -1 : 0);
}

void do_zero_gt(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t a = data_pop();
    data_push(a > 0 ? -1 : 0);
}

// I/O
void do_dot(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    printf("%" PRId64 " ", data_pop());
    fflush(stdout);
}

void do_cr(Word* w) {
    (void)w;
    printf("\n");
    fflush(stdout);
}

void do_emit(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    putchar((char)data_pop());
    fflush(stdout);
}

void do_key(Word* w) {
    (void)w;
    int c = getchar();
    data_push(c == EOF ? -1 : c);
}

void do_dot_quote(Word* w) {
    (void)w;
    if (state == 0) {
        // Interpret mode: print immediately
        if (input_ptr == NULL) { printf("Missing string\n"); return; }
        while (*input_ptr && isspace((unsigned char)*input_ptr)) input_ptr++;
        if (*input_ptr != '"') { printf("Expected \" to start string\n"); return; }
        input_ptr++;
        char* start = input_ptr;
        while (*input_ptr && *input_ptr != '"') input_ptr++;
        if (*input_ptr != '"') { printf("Unterminated string\n"); return; }
        while (start < input_ptr) putchar(*start++);
        input_ptr++;
        fflush(stdout);
    } else {
        // Compile mode: compile string for runtime
        if (input_ptr == NULL) { printf("Missing string\n"); return; }
        while (*input_ptr && isspace((unsigned char)*input_ptr)) input_ptr++;
        if (*input_ptr != '"') { printf("Expected \" to start string\n"); return; }
        input_ptr++;
        char* start = input_ptr;
        while (*input_ptr && *input_ptr != '"') input_ptr++;
        if (*input_ptr != '"') { printf("Unterminated string\n"); return; }
        size_t len = input_ptr - start;
        Word* inner_w = lookup_word_internal("do_dot_quote_inner");
        if (!inner_w) { printf("Fatal: do_dot_quote_inner not found\n"); return; }
        ensure_compile_cap(2 + (int32_t)len);
        compile_buf[compile_idx++] = (Cell){.word = inner_w};
        compile_buf[compile_idx++] = (Cell){.num = (int64_t)len};
        for (size_t i = 0; i < len; i++) {
            compile_buf[compile_idx++] = (Cell){.num = (int64_t)start[i]};
        }
        input_ptr++;
    }
}

void do_dot_quote_inner(Word* w) {
    (void)w;
    int64_t len = ip->num;
    ip++;
    for (int64_t i = 0; i < len; i++) {
        putchar((char)ip->num);
        ip++;
    }
    fflush(stdout);
}

void do_words(Word* w) {
    (void)w;
    printf("Dictionary words:\n");
    for (Word* cur = dict_head; cur != NULL; cur = cur->prev) {
        if (cur->flags & (1 << 6)) continue;
        printf("%s ", cur->name);
    }
    printf("\n");
    fflush(stdout);
}

// Memory operations
void do_fetch(Word* w) {
    (void)w;
    int64_t addr = data_pop();
    if (addr < 0 || addr >= user_mem_size) {
        printf("Address out of bounds\n");
        return;
    }
    data_push(user_mem[addr].num);
}

void do_store(Word* w) {
    (void)w;
    int64_t addr = data_pop();
    int64_t val = data_pop();
    if (addr < 0 || addr >= user_mem_size) {
        printf("Address out of bounds\n");
        return;
    }
    user_mem[addr].num = val;
}

void do_plus_store(Word* w) {
    (void)w;
    int64_t addr = data_pop();
    int64_t val = data_pop();
    if (addr < 0 || addr >= user_mem_size) {
        printf("Address out of bounds\n");
        return;
    }
    user_mem[addr].num += val;
}

void do_cfetch(Word* w) {
    (void)w;
    int64_t addr = data_pop();   // byte offset
    int64_t max_byte = user_mem_size * (int64_t)sizeof(Cell);
    if (addr < 0 || addr >= max_byte) {
        printf("Address out of bounds\n");
        return;
    }
    uint8_t* base = (uint8_t*)user_mem;
    data_push((int64_t)base[addr]);
}

void do_cstore(Word* w) {
    (void)w;
    int64_t addr = data_pop();
    int64_t val = data_pop();
    int64_t max_byte = user_mem_size * (int64_t)sizeof(Cell);
    if (addr < 0 || addr >= max_byte) {
        printf("Address out of bounds\n");
        return;
    }
    uint8_t* base = (uint8_t*)user_mem;
    base[addr] = (uint8_t)val;
}

void do_here(Word* w) {
    (void)w;
    // push the cell offset index
    data_push(here - user_mem);
}

void do_allot(Word* w) {
    (void)w;
    int64_t n = data_pop();
    if (here + n > user_mem + user_mem_size) {
        printf("User memory overflow\n");
        return;
    }
    here += n;
}

// Variable and constant
void do_variable(Word* w) {
    (void)w;
    char* name = next_token();
    if (!name) { printf("VARIABLE expects a name\n"); return; }

    // allocate one cell in user memory for the variable's data
    if (here + 1 > user_mem + user_mem_size) {
        printf("User memory overflow\n");
        return;
    }
    Cell* var_cell = here;    // address of the data cell
    var_cell->num = 0;        // initialise to 0 (optional)
    here++;

    // create dictionary entry
    Word* new_w = malloc(sizeof(Word));
    if (!new_w) { printf("Out of memory\n"); exit(1); }
    new_w->prev = dict_head;
    dict_head = new_w;

    size_t len = strlen(name);
    if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
    new_w->flags = (uint8_t)len;
    memcpy(new_w->name, name, len);
    new_w->name[len] = '\0';
    new_w->code = do_do_var;
    new_w->body = var_cell;   // body points directly to the data cell in user_mem
}

void do_constant(Word* w) {
    (void)w;
    int64_t val = data_pop();
    char* name = next_token();
    if (!name) { printf("CONSTANT expects a name\n"); data_push(val); return; }

    // allocate a cell in user memory to hold the constant value
    if (here + 1 > user_mem + user_mem_size) {
        printf("User memory overflow\n");
        data_push(val);       // restore the value (optional)
        return;
    }
    Cell* val_cell = here;
    val_cell->num = val;
    here++;

    Word* new_w = malloc(sizeof(Word));
    if (!new_w) { printf("Out of memory\n"); exit(1); }
    new_w->prev = dict_head;
    dict_head = new_w;

    size_t len = strlen(name);
    if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
    new_w->flags = (uint8_t)len;
    memcpy(new_w->name, name, len);
    new_w->name[len] = '\0';
    new_w->code = do_do_const;
    new_w->body = val_cell;   // body points to the cell that holds the value
}

void do_do_var(Word* w) {
    // push the address (cell index into user_mem) of the variable's data cell
    data_push(w->body - user_mem);
}

void do_do_const(Word* w) {
    data_push(w->body->num);   // push the constant value
}

// Return stack ops
void do_to_r(Word* w) {
    (void)w;
    int64_t val = data_pop();
    ret_push_num(val);
}

void do_r_from(Word* w) {
    (void)w;
    int64_t val = ret_pop_num();
    data_push(val);
}

void do_r_fetch(Word* w) {
    (void)w;
    if (rp < 0) { printf("Return stack underflow\n"); return; }
    data_push(ret_stack[rp].num);
}

// Control flow
void do_exit(Word* w) {
    (void)w;
    Cell* ret_addr = ret_pop_ip();
    ip = ret_addr;
}

void do_docolon(Word* w) {
    ret_push_ip(ip);
    ip = w->body;
}

void do_lit(Word* w) {
    (void)w;
    data_push(ip->num);
    ip++;
}

void do_colon(Word* w) {
    (void)w;
    char* name = next_token();
    if (!name) { printf("':' expects a name\n"); return; }
    size_t len = strlen(name);
    if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
    memcpy(compiling_name, name, len);
    compiling_name[len] = '\0';
    state = 1;
    compile_idx = 0;
    ensure_compile_cap(0);   // make sure compile_buf exists
}

void do_semicolon(Word* w) {
    (void)w;
    if (state != 1) { printf("';' only valid in compile mode\n"); return; }
    Word* exit_w = lookup_word("exit");
    if (!exit_w) { printf("Fatal: exit word not found\n"); return; }

    ensure_compile_cap(1);
    compile_buf[compile_idx++] = (Cell){.word = exit_w};

    // Create body copy of compiled cells
    Cell* body_copy = malloc(compile_idx * sizeof(Cell));
    if (!body_copy) { printf("Out of memory\n"); exit(1); }
    memcpy(body_copy, compile_buf, compile_idx * sizeof(Cell));

    // Create new word entry
    Word* new_w = malloc(sizeof(Word));
    if (!new_w) { printf("Out of memory\n"); free(body_copy); exit(1); }
    new_w->prev = dict_head;
    dict_head = new_w;

    size_t len = strlen(compiling_name);
    if (len > MAX_NAME_LEN) len = MAX_NAME_LEN;
    new_w->flags = (uint8_t)len;   // no hidden, no immediate
    memcpy(new_w->name, compiling_name, len);
    new_w->name[len] = '\0';
    new_w->code = do_docolon;
    new_w->body = body_copy;

    state = 0;   // back to interpret mode
}

void do_branch(Word* w) {
    (void)w;
    int64_t offset = ip->num;
    ip += offset;
}

void do_zero_branch(Word* w) {
    (void)w;
    int64_t cond = data_pop();
    if (cond == 0) {
        int64_t offset = ip->num;
        ip += offset;
    } else {
        ip++;
    }
}

// Control flow using compile stack (indices)
void do_if(Word* w) {
    (void)w;
    if (state != 1) { printf("IF only valid in compile mode\n"); return; }
    Word* zbranch = lookup_word_internal("0branch");
    if (!zbranch) { printf("Fatal: 0branch not found\n"); return; }
    ensure_compile_cap(2);
    compile_buf[compile_idx++] = (Cell){.word = zbranch};
    // compile_push current index (where the offset will be placed)
    compile_push(compile_idx);
    compile_idx++;   // reserve offset cell
}

void do_then(Word* w) {
    (void)w;
    if (state != 1) { printf("THEN only valid in compile mode\n"); return; }
    int64_t offset_idx = compile_pop();
    if (offset_idx < 0) return;
    compile_buf[offset_idx].num = compile_idx - offset_idx;
}

void do_else(Word* w) {
    (void)w;
    if (state != 1) { printf("ELSE only valid in compile mode\n"); return; }
    int64_t if_offset_idx = compile_pop();
    if (if_offset_idx < 0) return;

    Word* branch_w = lookup_word_internal("branch");
    if (!branch_w) { printf("Fatal: branch not found\n"); return; }
    ensure_compile_cap(2);

    // resolve IF offset to skip the ELSE branch
    compile_buf[if_offset_idx].num = (compile_idx + 2) - if_offset_idx;

    // compile unconditional branch for ELSE part
    compile_buf[compile_idx++] = (Cell){.word = branch_w};
    compile_push(compile_idx);
    compile_idx++;   // reserve offset cell
}

void do_begin(Word* w) {
    (void)w;
    if (state != 1) { printf("BEGIN only valid in compile mode\n"); return; }
    compile_push(compile_idx);
}

void do_until(Word* w) {
    (void)w;
    if (state != 1) { printf("UNTIL only valid in compile mode\n"); return; }
    int64_t begin_idx = compile_pop();
    if (begin_idx < 0) return;

    Word* zbranch = lookup_word_internal("0branch");
    if (!zbranch) { printf("Fatal: 0branch not found\n"); return; }
    ensure_compile_cap(2);
    compile_buf[compile_idx++] = (Cell){.word = zbranch};
    compile_buf[compile_idx++] = (Cell){.num = begin_idx - compile_idx};
}

void do_while(Word* w) {
    (void)w;
    if (state != 1) { printf("WHILE only valid in compile mode\n"); return; }
    int64_t begin_idx = compile_pop();
    if (begin_idx < 0) return;

    Word* zbranch = lookup_word_internal("0branch");
    if (!zbranch) { printf("Fatal: 0branch not found\n"); return; }
    ensure_compile_cap(2);
    compile_buf[compile_idx++] = (Cell){.word = zbranch};
    int64_t while_offset_idx = compile_idx;
    compile_idx++;   // reserve offset

    compile_push(while_offset_idx);
    compile_push(begin_idx);
}

void do_repeat(Word* w) {
    (void)w;
    if (state != 1) { printf("REPEAT only valid in compile mode\n"); return; }
    int64_t begin_idx = compile_pop();
    if (begin_idx < 0) return;
    int64_t while_offset_idx = compile_pop();
    if (while_offset_idx < 0) return;

    Word* branch_w = lookup_word_internal("branch");
    if (!branch_w) { printf("Fatal: branch not found\n"); return; }
    ensure_compile_cap(2);
    compile_buf[compile_idx++] = (Cell){.word = branch_w};
    compile_buf[compile_idx++] = (Cell){.num = begin_idx - compile_idx};

    compile_buf[while_offset_idx].num = compile_idx - while_offset_idx;
}

void do_depth(Word* w) {
    (void)w;
    data_push(data_sp + 1);
}

void do_pick(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t idx = data_pop();
    if (idx < 0 || idx > data_sp) return;
    int64_t value = data_stack[data_sp - (int32_t)idx];
    data_push(value);
}

void do_roll(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t n = data_pop();
    if (n == 0) return;
    if (n < 0 || n > data_sp) return;
    int64_t i = data_stack[data_sp - (int32_t)n];
    int32_t pos = (int32_t)(data_sp - (int32_t)n);
    while (pos < data_sp) {
        data_stack[pos] = data_stack[pos + 1];
        pos++;
    }
    data_stack[data_sp] = i;
}

void do_qdup(Word* w) {
    (void)w;
    if (data_sp < 0) return;
    int64_t v = data_pop();
    if (v != 0) {
        data_push(v);
        data_push(v);
    }
}

void do_2dup(Word* w) {
    (void)w;
    if (data_sp < 1) return;
    int64_t b = data_stack[data_sp];
    int64_t a = data_stack[data_sp - 1];
    data_push(a);
    data_push(b);
}

void do_2drop(Word* w) {
    (void)w;
    data_pop();
    data_pop();
}

void do_2swap(Word* w) {
    (void)w;
    if (data_sp < 3) return;
    int64_t d = data_pop(); // x4
    int64_t c = data_pop(); // x3
    int64_t b = data_pop(); // x2
    int64_t a = data_pop(); // x1
    data_push(b);
    data_push(a);
    data_push(d);
    data_push(c);
}