cemc 0.1.1

/**
 * Cem Runtime - Async I/O Implementation
 */

#define _XOPEN_SOURCE 700
#include "io.h"
#include "scheduler.h"
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

// Forward declare I/O functions to avoid unistd.h (which conflicts with
// stack.h's dup())
extern ssize_t write(int fd, const void *buf, size_t count);
extern ssize_t read(int fd, void *buf, size_t count);

#define STDIN_FILENO 0
#define STDOUT_FILENO 1
#define STDERR_FILENO 2

// Make sure stdout and stdin are in non-blocking mode
static bool io_initialized = false;

static void ensure_nonblocking_io(void) {
  if (io_initialized)
    return;

  // Set stdout to non-blocking
  int flags = fcntl(STDOUT_FILENO, F_GETFL, 0);
  if (flags == -1 || fcntl(STDOUT_FILENO, F_SETFL, flags | O_NONBLOCK) == -1) {
    runtime_error("ensure_nonblocking_io: failed to set stdout non-blocking");
  }

  // Set stdin to non-blocking
  flags = fcntl(STDIN_FILENO, F_GETFL, 0);
  if (flags == -1 || fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK) == -1) {
    runtime_error("ensure_nonblocking_io: failed to set stdin non-blocking");
  }

  io_initialized = true;
}

/**
 * Write a string to stdout with newline
 * Stack effect: ( str -- )
 *
 * Phase 2b: Uses cleanup handlers to ensure buffer is freed even if
 * strand is terminated while blocked.
 */
StackCell *write_line(StackCell *stack) {
  ensure_nonblocking_io();

  // Pop string from stack
  if (!stack || stack->tag != TAG_STRING) {
    runtime_error("write_line: expected string on stack");
  }

  const char *str = stack->value.s;
  StackCell *rest = stack->next;

  // Calculate total length (string + newline)
  size_t str_len = strlen(str);
  size_t total_len = str_len + 1; // +1 for newline

  // Allocate buffer for string + newline
  char *buffer = malloc(total_len);
  if (!buffer) {
    runtime_error("write_line: out of memory");
  }
  memcpy(buffer, str, str_len);
  buffer[str_len] = '\n';

  // Register cleanup handler to free buffer if strand terminates while blocked
  strand_push_cleanup(free, buffer);

  // Free the string cell (we've copied the data)
  free_cell(stack);

  // Write the buffer, handling EWOULDBLOCK by yielding
  size_t written = 0;
  while (written < total_len) {
    ssize_t n = write(STDOUT_FILENO, buffer + written, total_len - written);

    if (n > 0) {
      written += n;
    } else if (n == -1) {
      if (errno == EAGAIN || errno == EWOULDBLOCK) {
        // Would block - yield to scheduler and wait for writability
        strand_block_on_write(STDOUT_FILENO);
        // When we resume, try again
      } else {
        // Real error
        strand_pop_cleanup(); // Remove cleanup handler before freeing manually
        free(buffer);
        runtime_error("write_line: write() failed");
      }
    } else {
      // n == 0, shouldn't happen for stdout
      strand_pop_cleanup(); // Remove cleanup handler before freeing manually
      free(buffer);
      runtime_error("write_line: unexpected write() return 0");
    }
  }

  // Success - remove cleanup handler and free buffer manually
  strand_pop_cleanup();
  free(buffer);
  return rest;
}

/**
 * Read a line from stdin
 * Stack effect: ( -- str )
 *
 * Phase 2b: Uses cleanup handlers to ensure buffer is freed even if
 * strand is terminated while blocked.
 */
StackCell *read_line(StackCell *stack) {
  ensure_nonblocking_io();

  // Buffer for reading (we'll grow it if needed)
  size_t capacity = 128;
  size_t length = 0;
  char *buffer = malloc(capacity);
  if (!buffer) {
    runtime_error("read_line: out of memory");
  }

  // Register cleanup handler to free buffer if strand terminates while blocked
  strand_push_cleanup(free, buffer);

  // Read until we get a newline or EOF
  bool done = false;
  while (!done) {
    // Try to read one character at a time
    // (This is inefficient but simple for now; we could optimize later)
    char c;
    ssize_t n = read(STDIN_FILENO, &c, 1);

    if (n > 0) {
      // Got a character
      if (c == '\n') {
        done = true;
      } else {
        // Add to buffer
        if (length >= capacity) {
          capacity *= 2;
          char *new_buffer = realloc(buffer, capacity);
          if (!new_buffer) {
            strand_pop_cleanup(); // Remove cleanup handler before freeing
                                  // manually
            free(buffer);
            runtime_error("read_line: out of memory");
          }
          // Update cleanup handler with new buffer pointer atomically
          buffer = new_buffer;
          strand_update_cleanup_arg(buffer);
        }
        buffer[length++] = c;
      }
    } else if (n == 0) {
      // EOF
      done = true;
    } else {
      // n == -1
      if (errno == EAGAIN || errno == EWOULDBLOCK) {
        // Would block - yield to scheduler and wait for readability
        strand_block_on_read(STDIN_FILENO);
        // When we resume, try again
      } else {
        // Real error
        strand_pop_cleanup(); // Remove cleanup handler before freeing manually
        free(buffer);
        runtime_error("read_line: read() failed");
      }
    }
  }

  // Null-terminate the string
  if (length >= capacity) {
    capacity++;
    char *new_buffer = realloc(buffer, capacity);
    if (!new_buffer) {
      strand_pop_cleanup(); // Remove cleanup handler before freeing manually
      free(buffer);
      runtime_error("read_line: out of memory");
    }
    // Update cleanup handler with new buffer pointer atomically
    buffer = new_buffer;
    strand_update_cleanup_arg(buffer);
  }
  buffer[length] = '\0';

  // Create string cell and transfer ownership of buffer
  StackCell *result = alloc_cell();
  result->tag = TAG_STRING;
  result->value.s = buffer; // Transfer ownership to string cell
  result->next = stack;

  // Buffer ownership transferred to string cell, so remove cleanup handler
  // (the string cell will be freed by normal stack cleanup)
  strand_pop_cleanup();

  return result;
}