From 96115b347e480c9adfa177f045c9d7033c637811 Mon Sep 17 00:00:00 2001
From: samsonium <me@samsonium.ru>
Date: Sat, 10 Oct 2026 03:56:00 +0300
Subject: [PATCH] feat: implement file writer

---
 CMakeLists.txt                |  1 +
 include/compiler/fzl_writer.h | 25 ++++++++++++
 src/compiler/fzl_writer.c     | 72 +++++++++++++++++++++++++++++++++++
 src/compiler/main.c           | 41 +++++++++++++++++++-
 4 files changed, 138 insertions(+), 1 deletion(-)
 create mode 100644 include/compiler/fzl_writer.h
 create mode 100644 src/compiler/fzl_writer.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4b60a09..0013498 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,6 +13,7 @@ add_executable(fzc
 	src/compiler/fzl_parser.c
 	src/compiler/fzl_debug.c
 	src/compiler/fzl_walker.c
+	src/compiler/fzl_writer.c
 	src/compiler/utils/fzl_const_pool.c
 	src/compiler/main.c)
 
diff --git a/include/compiler/fzl_writer.h b/include/compiler/fzl_writer.h
new file mode 100644
index 0000000..f8184fd
--- /dev/null
+++ b/include/compiler/fzl_writer.h
@@ -0,0 +1,25 @@
+#ifndef FZL_WRITER_H
+#define FZL_WRITER_H
+
+#include <compiler/fzl_walker.h>
+#include <compiler/utils/fzl_const_pool.h>
+
+// File writer descriptor
+typedef struct
+{
+  const char *filepath;
+} fzl_writer_t;
+
+// Allocate writer
+fzl_writer_t *fzl_mkwriter(const char *filepath);
+
+// Write out a file
+int fzl_write(fzl_writer_t *writer, fzl_walker_t *walker);
+
+// Get last writer error message
+char *fzl_writer_geterror();
+
+// Free writer
+void fzl_freewriter(fzl_writer_t *writer);
+
+#endif // FZL_WRITER_H
diff --git a/src/compiler/fzl_writer.c b/src/compiler/fzl_writer.c
new file mode 100644
index 0000000..22ec471
--- /dev/null
+++ b/src/compiler/fzl_writer.c
@@ -0,0 +1,72 @@
+#include <compiler/fzl_writer.h>
+#include <compiler/utils/fzl_const_pool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char wrlast_err[256];
+
+fzl_writer_t *fzl_mkwriter(const char *filepath)
+{
+  if (strlen(filepath) < 1)
+    return NULL;
+
+  fzl_writer_t *writer = malloc(sizeof(fzl_writer_t));
+  if (!writer)
+    return NULL;
+
+  writer->filepath = filepath;
+
+  return writer;
+}
+
+int fzl_write(fzl_writer_t *writer, fzl_walker_t *walker)
+{
+  if (!writer || !walker)
+    return -1;
+
+  FILE *fp = fopen(writer->filepath, "wb");
+  if (!fp)
+  {
+    snprintf(wrlast_err, sizeof(wrlast_err), "failed to open '%s' to write",
+             writer->filepath);
+    return -1;
+  }
+
+  const char hdr[5] = {'F', 'Z', 'L', 0x0, 0x1};
+  fwrite(hdr, sizeof(char), 5, fp);
+  fwrite(&walker->consts->size, sizeof(size_t), 1, fp);
+  fwrite(&walker->op_count, sizeof(size_t), 1, fp);
+
+  for (size_t i = 0; i < walker->consts->size; i++)
+  {
+    fzl_const_t c = walker->consts->array[i];
+    fwrite(&c.type, sizeof(fzl_consttype_t), 1, fp);
+
+    if (c.type == FZL_CONSTTYPE_STRING)
+    {
+      size_t strlen = c.as.string.length;
+      fwrite(&c.as.string.length, sizeof(size_t), 1, fp);
+      fwrite(c.as.string.chars, sizeof(char), strlen, fp);
+    }
+  }
+
+  if (walker->op_count > 0)
+    fwrite(walker->ops, sizeof(uint64_t), walker->op_count, fp);
+
+  fclose(fp);
+
+  return 0;
+}
+
+char *fzl_writer_geterror() { return wrlast_err; }
+
+void fzl_freewriter(fzl_writer_t *writer)
+{
+  if (!writer)
+    return;
+
+  free(writer);
+}
diff --git a/src/compiler/main.c b/src/compiler/main.c
index 3407ec0..46c0689 100644
--- a/src/compiler/main.c
+++ b/src/compiler/main.c
@@ -2,6 +2,7 @@
 #include <compiler/fzl_parser.h>
 #include <compiler/fzl_reader.h>
 #include <compiler/fzl_walker.h>
+#include <compiler/fzl_writer.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -11,6 +12,7 @@
 typedef struct
 {
   char *filepath;
+  char *outpath;
   bool verbose;
   bool help;
 } build_args_t;
@@ -32,6 +34,7 @@ build_args_t *getargs(int argc, char **argv)
     return NULL;
 
   args->filepath = NULL;
+  args->outpath = NULL;
   args->verbose = false;
   args->help = false;
 
@@ -53,6 +56,15 @@ build_args_t *getargs(int argc, char **argv)
       {
         args->verbose = true;
       }
+      else if (strcmp(argv[i], "-o") == 0 || strcmp(argv[i], "--out") == 0)
+      {
+        if (!argv[i + 1] || argv[i + 1][0] == '-')
+        {
+          printf("Error: file path is not specified.\n");
+          return NULL;
+        }
+        args->outpath = argv[++i];
+      }
       else
       {
         printf("Error: unknown argument '%s'\n", argv[i]);
@@ -156,7 +168,8 @@ int main(int argc, char **argv)
   {
     printf("ok!\n");
     fzl_debug_print_ast(parser->root);
-    printf("-> walking AST...");
+    printf("> building\n");
+    printf("-> walking AST...\n");
   }
 
   fzl_walker_t *walker = fzl_mkwalker(parser->root);
@@ -178,13 +191,39 @@ int main(int argc, char **argv)
     printf("--> Ops:\n");
     for (size_t i = 0; i < walker->op_count; i++)
       printf("---> %lu\n", walker->ops[i]);
+
+    printf("-> preparing final write\n");
   }
 
+  char outpath[256];
+  if (args->outpath)
+    strcpy(outpath, args->outpath);
+  else
+    strcpy(outpath, "a.fzlc");
+
+  if (args->verbose)
+  {
+    printf("-> output file path is: %s", outpath);
+    printf("-> writing file...");
+  }
+
+  fzl_writer_t *writer = fzl_mkwriter(outpath);
+  result = fzl_write(writer, walker);
+  if (result != 0)
+  {
+    printf("Error: %s\n", fzl_writer_geterror());
+    return -1;
+  }
+
+  if (args->verbose)
+    printf("ok!\n");
+
   free(args);
   fzl_freereader(rd);
   fzl_freeparser(parser);
   fzl_freeast(parser->root);
   fzl_freewalker(walker);
+  fzl_freewriter(writer);
 
   printf("done.\n");
   return 0;