#include "LuaEngine/LuaEngine.h"

#include "DirectoryWalker/DirectoryWalker.h"
#include "Dom/Dom.h"
#include "Logger/Logger.h"
#include "Logger/LuaLogger.h"
#include "Path/Path.h"
#include "Version/Version.h"

#include <lauxlib.h>
#include <lua.h>
#include <lualib.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>

typedef enum { SCRIPT_INLINE, SCRIPT_EXTERNAL } ScriptType;

typedef struct {
  char *source;
  ScriptType type;
  unsigned long line;
} LuaScript;

typedef struct {
  LuaScript *items;
  size_t length;
  size_t capacity;
} ScriptList;

static int is_lua_element(const xmlNode *node) {
  return node->type == XML_ELEMENT_NODE &&
         strcasecmp((const char *)node->name, "lua") == 0;
}

static char *duplicate_string(const char *value) {
  size_t length = strlen(value);
  char *copy = malloc(length + 1);

  if (copy != NULL) {
    memcpy(copy, value, length + 1);
  }
  return copy;
}

static int grow_script_list(ScriptList *scripts) {
  size_t larger_capacity;
  LuaScript *larger_items;

  if (scripts->capacity > SIZE_MAX / (2 * sizeof(*scripts->items))) {
    return -1;
  }

  larger_capacity = scripts->capacity == 0 ? 4 : scripts->capacity * 2;
  larger_items =
      realloc(scripts->items, larger_capacity * sizeof(*scripts->items));
  if (larger_items == NULL) {
    return -1;
  }

  scripts->items = larger_items;
  scripts->capacity = larger_capacity;
  return 0;
}

static int append_script(ScriptList *scripts, const char *source,
                         ScriptType type, unsigned long line) {
  LuaScript *script;

  if (scripts->length == scripts->capacity && grow_script_list(scripts) != 0) {
    return -1;
  }

  script = &scripts->items[scripts->length];
  script->source = duplicate_string(source);
  if (script->source == NULL) {
    return -1;
  }

  script->type = type;
  script->line = line;
  ++scripts->length;
  return 0;
}

static int collect_script(xmlNode *node, ScriptList *scripts) {
  xmlChar *source_path = xmlGetProp(node, BAD_CAST "src");
  xmlChar *code;
  int result;

  if (source_path != NULL) {
    result = append_script(scripts, (const char *)source_path, SCRIPT_EXTERNAL,
                           node->line);
    xmlFree(source_path);
    return result;
  }

  code = xmlNodeGetContent(node);
  result = append_script(scripts, code == NULL ? "" : (const char *)code,
                         SCRIPT_INLINE, node->line);
  xmlFree(code);
  return result;
}

static int collect_scripts(xmlNode *node, ScriptList *scripts) {
  for (; node != NULL; node = node->next) {
    if (is_lua_element(node)) {
      if (collect_script(node, scripts) != 0) {
        return -1;
      }
    } else if (collect_scripts(node->children, scripts) != 0) {
      return -1;
    }
  }
  return 0;
}

static void free_scripts(ScriptList *scripts) {
  size_t index;

  for (index = 0; index < scripts->length; ++index) {
    free(scripts->items[index].source);
  }
  free(scripts->items);
}

static char *make_chunk_name(const char *input_path, unsigned long line) {
  size_t input_length = strlen(input_path);
  size_t capacity;
  char *chunk_name;

  if (input_length > SIZE_MAX - 32) {
    return NULL;
  }
  capacity = input_length + 32;
  chunk_name = malloc(capacity);

  if (chunk_name != NULL) {
    snprintf(chunk_name, capacity, "@%s:%lu", input_path, line);
  }
  return chunk_name;
}

static int run_script(lua_State *lua, const LuaScript *script,
                      const char *input_path) {
  char *source_path = NULL;
  char *chunk_name = NULL;
  const char *display_path;
  int load_result;
  int result;

  if (script->type == SCRIPT_EXTERNAL) {
    source_path = path_resolve_from_file(input_path, script->source);
    if (source_path == NULL) {
      logger_error("unable to allocate Lua source path");
      return -1;
    }
    display_path = source_path;
    load_result = luaL_loadfile(lua, source_path);
  } else {
    chunk_name = make_chunk_name(input_path, script->line);
    if (chunk_name == NULL) {
      logger_error("unable to allocate Lua chunk name");
      return -1;
    }
    display_path = input_path;
    load_result = luaL_loadbuffer(lua, script->source, strlen(script->source),
                                  chunk_name);
  }

  result = load_result == 0 ? lua_pcall(lua, 0, 0, 0) : load_result;
  if (result != 0) {
    const char *message = lua_tostring(lua, -1);

    logger_error("Lua error in %s: %s", display_path,
                 message == NULL ? "unknown error" : message);
    lua_pop(lua, 1);
  }

  free(chunk_name);
  free(source_path);
  return result == 0 ? 0 : -1;
}

static int run_scripts(lua_State *lua, const ScriptList *scripts,
                       const char *input_path) {
  size_t index;

  for (index = 0; index < scripts->length; ++index) {
    if (run_script(lua, &scripts->items[index], input_path) != 0) {
      return -1;
    }
  }
  return 0;
}

static void register_yapssg(lua_State *lua) {
  lua_newtable(lua);
  lua_pushstring(lua, yapssg_version);
  lua_setfield(lua, -2, "version");
  lua_setglobal(lua, "yapssg");
}

static int replace_document_root(lua_State *lua, htmlDocPtr document,
                                 const char *input_path) {
  xmlNodePtr replacement;
  xmlNodePtr old_root;

  lua_getglobal(lua, "page");
  if (!lua_istable(lua, -1)) {
    logger_error("Lua global 'page' must remain a table: %s", input_path);
    lua_pop(lua, 1);
    return -1;
  }

  replacement = dom_page_from_lua(lua, lua_gettop(lua));
  lua_pop(lua, 1);
  if (replacement == NULL || replacement->type != XML_ELEMENT_NODE) {
    logger_error("Lua produced an invalid page root: %s", input_path);
    xmlFreeNode(replacement);
    return -1;
  }

  old_root = xmlDocSetRootElement(document, replacement);
  xmlFreeNode(old_root);
  return 0;
}

int process_html_document(htmlDocPtr document, const char *input_path) {
  xmlNodePtr root = xmlDocGetRootElement(document);
  ScriptList scripts = {0};
  lua_State *lua;
  int result;

  if (root == NULL) {
    logger_error("HTML document has no root element: %s", input_path);
    return -1;
  }
  if (collect_scripts(root, &scripts) != 0) {
    logger_error("unable to collect Lua scripts: %s", input_path);
    free_scripts(&scripts);
    return -1;
  }
  if (scripts.length == 0) {
    free_scripts(&scripts);
    return 0;
  }

  lua = luaL_newstate();
  if (lua == NULL) {
    logger_error("unable to create Lua state");
    free_scripts(&scripts);
    return -1;
  }

  luaL_openlibs(lua);
  register_yapssg(lua);
  lua_logger_register(lua);
  directory_walker_register(lua, input_path);
  dom_push_page(lua, root);
  lua_setglobal(lua, "page");

  result = run_scripts(lua, &scripts, input_path);
  if (result == 0) {
    result = replace_document_root(lua, document, input_path);
  }

  lua_close(lua);
  free_scripts(&scripts);
  return result;
}