/*
 * resolv_manager.c
 * This file is part of Network-inador
 *
 * Copyright (C) 2022 - Félix Arreola Rodríguez
 *
 * Network-inador is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Network-inador is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Network-inador; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, 
 * Boston, MA  02110-1301  USA
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <ctype.h>
#include <sys/inotify.h>
#include <sys/types.h>
#include <arpa/inet.h>

#include "resolv_manager.h"
#include "network-inador-private.h"
#include "utils.h"
#include "resolv_conf_parser.h"
#include "interfaces.h"
#include "file_watcher.h"

void resolv_manager_write (NetworkInadorHandle *handle);

int resolv_manager_sort_entries (const void *a, const void *b, void * data) {
	const ResolvConfEntry *aa = (ResolvConfEntry *) a;
	const ResolvConfEntry *bb = (ResolvConfEntry *) b;
	
	/* Primero, las purgadas van al final */
	if (aa->for_purge == 1 && bb->for_purge == 0) {
		return 1;
	} else if (aa->for_purge == 0 && bb->for_purge == 1) {
		return -1;
	} else if (aa->for_purge == 1) {
		return 0;
	}
	if (aa->tagged == 1 && bb->tagged == 0) {
		/* TODO: Revisar este orden por prioridades */
		return -1;
	} else if (aa->tagged == 0 && bb->tagged == 1) {
		return 1;
	} else if (aa->tagged == 1) {
		/* Como los dos están en el archivo, comparar por el file_order */
		return (aa->file_order - bb->file_order);
	}
	
	/* TODO: Estas entradas necesitan resolverse por prioridad de configuración */
	return 0;
}

void resolv_manager_clear_entries_by_prog (NetworkInadorHandle *handle, const int iface_index, const char *prog) {
	FList *g;
	ResolvConfEntry *entry;
	int do_write = 0;
	
	g = handle->resolver_entries;
	while (g != NULL) {
		entry = (ResolvConfEntry *) g->data;
		
		if (entry->origin != RESOLV_ORIGIN_RESOLVCONF || entry->owner_interface_index != iface_index) {
			/* Solo borramos las entradas creadas via resolvconf y que pertenezcan a esta interfaz */
			g = g->next;
			continue;
		}
		
		if (prog == NULL || strcmp (entry->owner_prog, prog) == 0) {
			/* Hay que eliminar esta entrada, coincide por la interfaz o nombre de programa */
			printf ("/// Eliminando entrada %s por via resolvconf. Prog = «%s»\n", entry->value, prog);
			/*free (entry);
			
			handle->resolver_entries = f_list_delete_link (handle->resolver_entries, g);*/
			entry->for_purge = 1;
			do_write = 1;
		}
		
		g = g->next;
	}
	
	/* Solicitar una escritura del archivo, via el resolvconf fuimos modificados */
	if (do_write == 1) {
		resolv_manager_write (handle);
	}
}

void resolv_manager_clear_tag_on_all (NetworkInadorHandle *handle) {
	FList *pos;
	ResolvConfEntry *entry;
	
	/* Borrar el atributo "tagged" */
	pos = handle->resolver_entries;
	while (pos != NULL) {
		entry = (ResolvConfEntry *) pos->data;
		
		entry->tagged = 0;
		entry->was_new = 0;
		pos = pos->next;
	}
}

void resolv_manager_process_resolvconf_entries (NetworkInadorHandle *handle, void *entries) {
	ResolvConfEntry *new_entry, *found_entry;
	FList *g, *pos_searched_entry;
	int do_write = 0;
	int n;
	
	resolv_manager_clear_tag_on_all (handle);
	
	g = entries;
	n = 0;
	while (g != NULL) {
		new_entry = (ResolvConfEntry *) g->data;
		
		found_entry = NULL;
		while (found_entry == NULL) {
			pos_searched_entry = resolv_parser_search_entry (handle->resolver_entries, new_entry->resolv_type, new_entry->ns_family, &new_entry->nameserver, new_entry->value, 1);
			if (pos_searched_entry == NULL) break;
			
			/* De ser posible, hacer conciliación */
			found_entry = (ResolvConfEntry *) pos_searched_entry->data;
			
			if (found_entry->origin == RESOLV_ORIGIN_FILE) {
				/* Hacer esta entrada nuestra */
				found_entry->origin = RESOLV_ORIGIN_RESOLVCONF;
				found_entry->owner_interface_index = new_entry->owner_interface_index;
				found_entry->tagged = 1;
				strncpy (found_entry->owner_prog, new_entry->owner_prog, sizeof (found_entry->owner_prog));
				printf ("/// Asociando una entrada %s existente del archivo al: %s\n", found_entry->value, found_entry->owner_prog);
			#if 0
			} else if (found_entry->origin == RESOLV_ORIGIN_DHCP) {
				/* Una entrada que coincide con la actual solo se puede re-asociar al resolvconf si pertenece a la misma interfaz */
				if (found_entry->owner_interface_index != new_entry->owner_interface_index) {
					found_entry->tagged = 1;
					found_entry = NULL;
					continue;
				}
			#endif
			} else {
				/* Existe la entrada, pero no la podemos tomar como nuestra, crear otra */
				found_entry->tagged = 1;
				found_entry = NULL;
				continue;
			}
		}
		
		/* Si no existe, crearla */
		if (found_entry == NULL) {
			found_entry = (ResolvConfEntry *) malloc (sizeof (ResolvConfEntry));
			
			memcpy (found_entry, new_entry, sizeof (ResolvConfEntry));
			found_entry->file_order = n; /* TODO: Revisar esto del file order */
			found_entry->tagged = 0;
			found_entry->priority = 0;
			found_entry->for_purge = 0;
			
			/* Anexar al final de la lista */
			handle->resolver_entries = f_list_append (handle->resolver_entries, found_entry);
			
			/* TODO: Como creamos una entrada via el resolvconf, regenerar el archivo */
			printf ("/// Nueva entrada %s via resolvconf, programando regeneración.\n", found_entry->value);
			do_write = 1;
		}
		
		g = g->next;
	}
	
	/* Si hubo actualización cambios, disparar ahora */
	if (do_write == 1) {
		resolv_manager_write (handle);
	}
}

void resolv_manager_process_dhcp_nameservers (NetworkInadorHandle *handle, Interface *iface) {
	FList *pos_entry;
	int h;
	ResolvConfEntry *entry;
	int do_write = 0;
	
	/* Recorrer todas las entradas que sean tipo DHCP y marcar para eliminación */
	resolv_manager_clear_tag_on_all (handle);
	
	pos_entry = handle->resolver_entries;
	while (pos_entry != NULL) {
		entry = (ResolvConfEntry *) pos_entry->data;
		
		if (entry->origin == RESOLV_ORIGIN_DHCP && entry->owner_interface_index == iface->index) {
			/* Nos interesa para eliminación */
			entry->for_purge = 1;
		}
		
		pos_entry = pos_entry->next;
	}
	
	/* Ahora, procesar la información de DHCP buscando entradas (viejas o de archivo) para reciclar.
	 * Si no, crear */
	for (h = 0; h < iface->dhcpc.dns_c; h++) {
		entry = NULL;
		while (entry == NULL) {
			pos_entry = resolv_parser_search_entry (handle->resolver_entries, RESOLV_TYPE_NAMESERVER, AF_INET, &iface->dhcpc.dns[h], "", 1);
			if (pos_entry == NULL) break;
			
			/* De ser posible, hacer conciliación */
			entry = (ResolvConfEntry *) pos_entry->data;
			
			if (entry->origin == RESOLV_ORIGIN_FILE) {
				/* Hacer esta entrada nuestra */
				entry->origin = RESOLV_ORIGIN_DHCP;
				entry->owner_interface_index = iface->index;
				entry->tagged = 1;
				entry->owner_prog[0] = 0;
				printf ("/// Asociando una entrada %s existente del archivo al DHCP (%s)\n", entry->value, iface->name);
			} else if (entry->origin == RESOLV_ORIGIN_DHCP && entry->owner_interface_index == iface->index) {
				/* Una entrada vieja coincide, reciclar */
				entry->tagged = 1;
				entry->for_purge = 0;
			} else {
				/* Existe la entrada, pero no la podemos tomar como nuestra, buscar otra */
				entry->tagged = 1;
				entry = NULL;
				continue;
			}
		}
		
		/* Si la entrada no se pudo conciliar, crear una */
		if (entry == NULL) {
			entry = (ResolvConfEntry *) malloc (sizeof (ResolvConfEntry));
			
			entry->resolv_type = RESOLV_TYPE_NAMESERVER;
			entry->origin = RESOLV_ORIGIN_DHCP;
			entry->owner_interface_index = iface->index;
			entry->owner_prog[0] = 0;
			entry->file_order = h;
			entry->tagged = 0;
			entry->priority = 0;
			entry->for_purge = 0;
			entry->ns_family = AF_INET;
			memcpy (&entry->nameserver, &iface->dhcpc.dns[h], 4);
			inet_ntop (AF_INET, &entry->nameserver, entry->value, sizeof (entry->value));
			
			/* Anexar al final de la lista */
			handle->resolver_entries = f_list_append (handle->resolver_entries, entry);
			
			/* Como creamos una entrada via el dhcp, regenerar el archivo */
			printf ("/// Nueva entrada %s via DHCP (%s), programando regeneración.\n", entry->value, iface->name);
			do_write = 1;
		}
	}
	
	/* Si tiene un nombre de dominio, agregar como entrada tipo search */
	if (iface->dhcpc.domain_name[0] != 0) {
		entry = NULL;
		while (entry == NULL) {
			pos_entry = resolv_parser_search_entry (handle->resolver_entries, RESOLV_TYPE_SEARCH, AF_INET, NULL, iface->dhcpc.domain_name, 1);
			if (pos_entry == NULL) break;
			
			/* De ser posible, hacer conciliación */
			entry = (ResolvConfEntry *) pos_entry->data;
			
			if (entry->origin == RESOLV_ORIGIN_FILE) {
				/* Hacer esta entrada nuestra */
				entry->origin = RESOLV_ORIGIN_DHCP;
				entry->owner_interface_index = iface->index;
				entry->tagged = 1;
				entry->owner_prog[0] = 0;
				printf ("/// Asociando una entrada search %s existente del archivo al DHCP (%s)\n", entry->value, iface->name);
			} else if (entry->origin == RESOLV_ORIGIN_DHCP && entry->owner_interface_index == iface->index) {
				/* Una entrada vieja coincide, reciclar */
				entry->tagged = 1;
				entry->for_purge = 0;
			} else {
				/* Existe la entrada, pero no la podemos tomar como nuestra, buscar otra */
				entry->tagged = 1;
				entry = NULL;
				continue;
			}
		}
		
		/* Si la entrada no se pudo conciliar, crear una */
		if (entry == NULL) {
			entry = (ResolvConfEntry *) malloc (sizeof (ResolvConfEntry));
			
			entry->resolv_type = RESOLV_TYPE_SEARCH;
			entry->origin = RESOLV_ORIGIN_DHCP;
			entry->owner_interface_index = iface->index;
			entry->owner_prog[0] = 0;
			entry->file_order = h;
			entry->tagged = 0;
			entry->priority = 0;
			entry->for_purge = 0;
			entry->ns_family = AF_INET;
			memset (&entry->nameserver, 0, sizeof (entry->nameserver));
			strncpy (entry->value, iface->dhcpc.domain_name, sizeof (entry->value));
			
			/* Anexar al final de la lista */
			handle->resolver_entries = f_list_append (handle->resolver_entries, entry);
			
			/* Como creamos una entrada via el dhcp, regenerar el archivo */
			printf ("/// Nueva entrada search %s via DHCP (%s), programando regeneración.\n", entry->value, iface->name);
			do_write = 1;
		}
	}
	
	/* Después de recorrer las entradas, revisar si quedaron entradas por purgar.
	 * Si hay entradas por purgar, programar una reescritura de archivo */
	pos_entry = handle->resolver_entries;
	while (pos_entry != NULL) {
		entry = (ResolvConfEntry *) pos_entry->data;
		
		if (entry->for_purge == 1) {
			do_write = 1;
			printf ("/// Entrada %s eliminada via DHCP (%s), programando regeneración.\n", entry->value, iface->name);
			//break;
		}
		pos_entry = pos_entry->next;
	}
	
	if (do_write) {
		resolv_manager_write (handle);
	}
}

void resolv_manager_clear_dhcp_nameservers (NetworkInadorHandle *handle, Interface *iface) {
	FList *pos_entry;
	int h;
	ResolvConfEntry *entry;
	int do_write = 0;
	
	/* Recorrer todas las entradas que sean tipo DHCP y marcar para eliminación */
	resolv_manager_clear_tag_on_all (handle);
	
	pos_entry = handle->resolver_entries;
	while (pos_entry != NULL) {
		entry = (ResolvConfEntry *) pos_entry->data;
		
		if (entry->origin == RESOLV_ORIGIN_DHCP && entry->owner_interface_index == iface->index) {
			/* Nos interesa para eliminación */
			printf ("/// Entrada %s eliminada via DHCP (%s), programando regeneración.\n", entry->value, iface->name);
			entry->for_purge = 1;
			do_write = 1;
		}
		
		pos_entry = pos_entry->next;
	}
	
	if (do_write) {
		resolv_manager_write (handle);
	}
}

void resolv_manager_read_local_etc_resolv (NetworkInadorHandle *handle) {
	FILE *fd;
	FList *pos, *next;
	ResolvConfEntry *entry;
	
	fd = fopen ("/etc/resolv.conf", "r");
	if (fd == NULL) return;
	
	printf ("/// Ejecutando lectura de resolv.conf\n");
	/* Etiquetar las entradas con origen del archivo como "ya no en el archivo", para que cuando se lea el archivo, nos queden las que vamos a eliminar */
	resolv_manager_clear_tag_on_all (handle);
	
	handle->resolver_entries = resolv_parser_parse_local_file (handle->resolver_entries, fd, RESOLV_ORIGIN_FILE);
	
	fclose (fd);
	
	/* A la salida, borrar las que ya no siguen en el archivo */
	pos = handle->resolver_entries;
	while (pos != NULL) {
		next = pos->next;
		entry = (ResolvConfEntry *) pos->data;
		
		if (entry->origin == RESOLV_ORIGIN_FILE && entry->tagged == 0) {
			/* Esta entrada se va, la eliminaron */
			printf ("/// La entrada %s del resolv.conf fué eliminada del archivo. Purgando nosotros.\n", entry->value);
			
			entry->for_purge = 1;
			handle->resolver_entries = f_list_delete_link (handle->resolver_entries, pos);
			free (entry);
			entry = NULL;
		} else {
			if (entry->was_new) {
				printf ("/// La entrada %s es nueva en el resolv.conf\n", entry->value);
			} else {
				printf ("/// La entrada %s del resolv.conf sigue en el archivo.\n", entry->value);
			}
		}
		pos = next;
	}
	
	/* Reordenar las entradas. TODO: Falta leer los ficheros de configuración del resolv.conf */
	handle->resolver_entries = f_list_sort_with_data (handle->resolver_entries, resolv_manager_sort_entries, NULL);
}

void resolv_manager_write (NetworkInadorHandle *handle) {
	FILE *fd;
	FList *pos, *next;
	ResolvConfEntry *entry;
	Interface *iface;
	
	/* Antes de hacer la escritura, siempre hacemos una lectura */
	printf ("/// Ejecutando pre-lectura de resolv.conf para poderlo modificar\n");
	resolv_manager_read_local_etc_resolv (handle);
	
	/* Intentar la escritura */
	fd = fopen ("/etc/resolv.conf", "w");
	if (fd != NULL) {
		fprintf (fd, "# Autogenered by NetworkInador, you can change this file, changes are preserved");
		fprintf (fd, "\n\n");
		
		pos = handle->resolver_entries;
		while (pos != NULL) {
			entry = (ResolvConfEntry *) pos->data;
			
			if (entry->for_purge == 1) {
				/* Omitir */
				pos = pos->next;
				continue;
			}
			
			iface = _interfaces_locate_by_index (handle->interfaces, entry->owner_interface_index);
			/* Escribir esta entrada "buena" al resolv.conf */
			if (entry->origin == RESOLV_ORIGIN_FILE) {
				fprintf (fd, "# This entry was previously on file, preserving");
			} else if (entry->origin == RESOLV_ORIGIN_DHCP) {
				fprintf (fd, "# This entry was added via DHCP (on %s) by NetworkInador", (iface != NULL ? iface->name : "unknown"));
			} else if (entry->origin == RESOLV_ORIGIN_RESOLVCONF) {
				fprintf (fd, "# This entry was added via resolvconf (%s.%s)", (iface != NULL ? iface->name : "unknown"), entry->owner_prog);
			} else if (entry->origin == RESOLV_ORIGIN_SLAAC_RDNSS) {
				fprintf (fd, "# This entry was added via RDNSS (IPv6)");
			}
			fprintf (fd, "\n");
			
			if (entry->resolv_type == RESOLV_TYPE_NAMESERVER) {
				fprintf (fd, "nameserver %s\n", entry->value);
			} else if (entry->resolv_type == RESOLV_TYPE_DOMAIN) {
				fprintf (fd, "domain %s\n", entry->value);
			} else if (entry->resolv_type == RESOLV_TYPE_SEARCH) {
				fprintf (fd, "search %s\n", entry->value);
			} else if (entry->resolv_type == RESOLV_TYPE_SORTLIST) {
				fprintf (fd, "sortlist %s\n", entry->value);
			} else if (entry->resolv_type == RESOLV_TYPE_OPTIONS) {
				fprintf (fd, "options %s\n", entry->value);
			}
			pos = pos->next;
		}
		
		fclose (fd);
	}
	
	/* Purgar las entradas marcadas para purge */
	pos = handle->resolver_entries;
	while (pos != NULL) {
		next = pos->next;
		entry = (ResolvConfEntry *) pos->data;
		
		if (entry->for_purge == 1) {
			handle->resolver_entries = f_list_delete_link (handle->resolver_entries, pos);
			free (entry);
			entry = NULL;
		}
		pos = next;
	}
}

void resolv_manager_notify_close_write_cb (NetworkInadorHandle *handle, const char *path, void *data) {
	/* Cuando se nos notifique acerca de un cambio en el resolv.conf re-leer el archivo */
	resolv_manager_read_local_etc_resolv (handle);
}

void resolv_manager_init (NetworkInadorHandle *handle) {
	network_inador_file_watcher_add_file (handle, "/etc/resolv.conf", resolv_manager_notify_close_write_cb, NULL);
	 
	handle->resolver_entries = NULL;
	/* Luego, leer el resolv.conf */
	resolv_manager_read_local_etc_resolv (handle);
}