#include "container.h"
#include "image.h"
#include "disk.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/statvfs.h>

result_t check_container_identifier(const char* identifier) {
	result_t result;

	// Check that the identifier is not null.
	if (identifier == NULL) {
		result = failure("The specified container identifier is null.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Check that the identifier is not empty.
	size_t length = strlen(identifier);
	if (length == 0) {
		result = failure("The specified container identifier is empty.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Check that the identifier is not too long.
	if (length > MAX_CONTAINER_IDENTIFIER_LENGTH) {
		result = failure("The specified container identifier is too long (maximum length is %d).", MAX_CONTAINER_IDENTIFIER_LENGTH);
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Check that the identifier contains only alphanumeric characters and underscores.
	for (size_t i = 0; i < length; i++) {
		if (isalnum(identifier[i]))
			continue;
		if ((identifier[i] == '_' || identifier[i] == '-' || identifier[i] == '.') && i > 0)
			continue;

		result = failure("The specified container identifier contains an invalid character '%c' at index %zu.", identifier[i], i);
		verbose("Exception -> %s", last_error());

		return result;
	}

	return success();
}

result_t check_container_exists(bool* _exists, const config_t* config, const char* identifier) {
	result_t result;

	// Get the container path.
	char* path;
	result = get_container_path(&path, config, identifier);
	if (result != success()) {
		result = failure("Failed to get the container path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Check that the container exists.
	struct stat st;
	if (stat(path, &st) == -1) {
		if (errno == ENOENT) {
			free(path);

			// The container does not exist.
			*_exists = false;

			verbose("The container '%s' does not exist.", identifier);

			return success();
		}

		result = failure("Failed to check whether the container exists.");
		verbose("Exception -> %s", last_error());

		free(path);

		return result;
	}

	free(path);

	// Check that the container is a regular file.
	if (!S_ISREG(st.st_mode)) {
		result = failure("The specified container path is not a regular file.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// The container exists and is a regular file.
	*_exists = true;

	verbose("The container '%s' exists.", identifier);

	return success();
}

result_t get_container_pool_path(char** _path, const config_t* config) {
	result_t result;

	// Check that the configuration is not null.
	if (config == NULL) {
		result = failure("The specified program configuration is null.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Create a copy of the container pool path.
	char* path = strdup(config->container_pool);
	if (path == NULL) {
		result = failure("Failed to copy the container pool path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Set the container pool path.
	*_path = path;

	return success();
}

result_t get_container_path(char** _path, const config_t* config, const char* identifier) {
	result_t result;

	// Check that the identifier is valid.
	result = check_container_identifier(identifier);
	if (result != success()) {
		result = failure("The specified container identifier is invalid.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the container pool path.
	char* container_pool;
	result = get_container_pool_path(&container_pool, config);
	if (result != success()) {
		result = failure("Failed to get the container pool path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Append the identifier to the container pool path.
	char* path;
	if (asprintf(&path, "%s/%s", container_pool, identifier) == -1) {
		result = failure("Failed to allocate memory for the container path.");
		verbose("Exception -> %s", last_error());

		free(container_pool);

		return result;
	}

	// Free the container pool path.
	free(container_pool);

	// Set the container path.
	*_path = path;

	return success();
}

result_t add_root_container(const config_t* config, const char* identifier, size_t size) {
	result_t result;

	// Check that the container does not already exist.
	bool exists;
	result = check_container_exists(&exists, config, identifier);
	if (result != success()) {
		result = failure("Failed to check whether the container exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	if (exists) {
		result = failure("The specified container already exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the container path.
	char* path;
	result = get_container_path(&path, config, identifier);
	if (result != success()) {
		result = failure("Failed to get the container path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Create the container disk.
	result = create_root_disk(path, size);
	if (result != success()) {
		result = failure("Failed to create the container disk.");
		verbose("Exception -> %s", last_error());

		free(path);

		return result;
	}

	// Free the container path.
	free(path);

	verbose("Successfully added root container '%s' to the container pool, with a size of %zu bytes.", identifier, size);

	return success();
}

result_t add_backed_container(const config_t* config, const char* identifier, const char* image) {
	result_t result;

	// Check that the container does not already exist.
	bool exists;
	result = check_container_exists(&exists, config, identifier);
	if (result != success()) {
		result = failure("Failed to check whether the container exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	if (exists) {
		result = failure("The specified container already exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the container path.
	char* path;
	result = get_container_path(&path, config, identifier);
	if (result != success()) {
		result = failure("Failed to get the container path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the image path.
	char* image_path;
	result = get_image_path(&image_path, config, image);
	if (result != success()) {
		result = failure("Failed to get the image path.");
		verbose("Exception -> %s", last_error());

		free(path);

		return result;
	}

	// Create the container disk.
	result = create_backed_disk(path, image_path);
	if (result != success()) {
		result = failure("Failed to create the container disk.");
		verbose("Exception -> %s", last_error());

		free(image_path);
		free(path);

		return result;
	}

	// Free the image path.
	free(image_path);

	// Free the container path.
	free(path);

	verbose("Successfully added backed container '%s' to the container pool, backed by the image '%s'.", identifier, image);

	return success();
}

result_t remove_container(const config_t* config, const char* identifier) {
	result_t result;

	// Check that the container exists.
	bool exists;
	result = check_container_exists(&exists, config, identifier);
	if (result != success()) {
		result = failure("Failed to check whether the container exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	if (!exists) {
		result = failure("The specified container does not exist.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the container path.
	char* path;
	result = get_container_path(&path, config, identifier);
	if (result != success()) {
		result = failure("Failed to get the container path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Remove the container disk.
	if (remove(path) == -1) {
		result = failure("Failed to remove the container disk (%s).", strerror(errno));
		verbose("Exception -> %s", last_error());

		free(path);

		return result;
	}

	// Free the container path.
	free(path);

	verbose("Successfully removed the container '%s' from the container pool.", identifier);

	return success();
}

result_t reset_container(const config_t* config, const char* identifier) {
	result_t result;

	// Check that the container exists.
	bool exists;
	result = check_container_exists(&exists, config, identifier);
	if (result != success()) {
		result = failure("Failed to check whether the container exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	if (!exists) {
		result = failure("The specified container does not exist.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the container path.
	char* path;
	result = get_container_path(&path, config, identifier);
	if (result != success()) {
		result = failure("Failed to get the container path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Reset the container disk.
	result = reset_disk(path);
	if (result != success()) {
		result = failure("Failed to reset the container disk.");
		verbose("Exception -> %s", last_error());

		free(path);

		return result;
	}

	// Free the container path.
	free(path);

	verbose("Successfully reset the container '%s'.", identifier);

	return success();
}

result_t trim_container(const config_t* config, const char* identifier) {
	result_t result;

	// Check that the container exists.
	bool exists;
	result = check_container_exists(&exists, config, identifier);
	if (result != success()) {
		result = failure("Failed to check whether the container exists.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	if (!exists) {
		result = failure("The specified container does not exist.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the container path.
	char* path;
	result = get_container_path(&path, config, identifier);
	if (result != success()) {
		result = failure("Failed to get the container path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Trim the container disk.
	result = trim_disk(path);
	if (result != success()) {
		result = failure("Failed to trim the container disk.");
		verbose("Exception -> %s", last_error());

		free(path);

		return result;
	}

	// Free the container path.
	free(path);

	verbose("Successfully trimmed the container '%s'.", identifier);

	return success();
}

result_t list_containers(char*** _identifiers, size_t* _count, const config_t* config) {
	result_t result;

	// Get the container pool path.
	char* container_pool;
	result = get_container_pool_path(&container_pool, config);
	if (result != success()) {
		result = failure("Failed to get the container pool path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	char** identifiers;
	size_t count;
	result = list_files(&identifiers, &count, container_pool, check_container_identifier);
	if (result != success()) {
		result = failure("Failed to list the containers in the pool.");
		verbose("Exception -> %s", last_error());

		free(container_pool);

		return result;
	}

	// Free the container pool path.
	free(container_pool);

	// Set the list of identifiers.
	if (_identifiers != NULL)
		*_identifiers = identifiers;
	else {
		for (size_t i = 0; i < count; i++)
			free(identifiers[i]);
		free(identifiers);
	}

	// Set the count of identifiers.
	if (_count != NULL)
		*_count = count;

	verbose("The container pool contains %zu containers.", count);

	return success();
}

result_t get_container_pool_space(size_t* _space, const config_t* config) {
	result_t result;

	// Get the container pool path.
	char* container_pool;
	result = get_container_pool_path(&container_pool, config);
	if (result != success()) {
		result = failure("Failed to get the container pool path.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Get the available space in the container pool.
	struct statvfs st;
	if (statvfs(container_pool, &st) == -1) {
		result = failure("Failed to get the available space in the container pool (%s).", strerror(errno));
		verbose("Exception -> %s", last_error());

		free(container_pool);

		return result;
	}

	// Free the container pool path.
	free(container_pool);

	// Set the available space.
	*_space = st.f_bsize * st.f_bavail;

	verbose("The available space in the container pool is %zu bytes.", st.f_bsize * st.f_bavail);

	return success();
}

result_t find_oldest_container(char** _identifier, const config_t* config) {
	result_t result;

	// Get the list of containers.
	char** identifiers;
	size_t count;
	result = list_containers(&identifiers, &count, config);
	if (result != success()) {
		result = failure("Failed to find the oldest container due to a failure to list the containers.");
		verbose("Exception -> %s", last_error());

		return result;
	}

	// Find the oldest container.
	time_t oldest_time = 0;
	char* oldest_identifier = NULL;

	for (size_t i = 0; i < count; i++) {
		// Get the container path.
		char* path;
		result = get_container_path(&path, config, identifiers[i]);
		if (result != success()) {
			verbose("Skipping the container '%s' due to an exception.", identifiers[i]);

			continue;
		}

		// Get the last access time of the container.
		struct stat st;
		if (stat(path, &st) == -1) {
			verbose("Skipping the container '%s' due to a failure to get the last access time.", identifiers[i]);

			free(path);

			continue;
		}

		// Check if the container is the oldest.
		if (oldest_identifier == NULL || st.st_mtime < oldest_time) {
			oldest_time = st.st_mtime;
			oldest_identifier = identifiers[i];
		}

		// Free the container path.
		free(path);
	}

	// Set the oldest container identifier.
	if (oldest_identifier != NULL) {
		oldest_identifier = strdup(oldest_identifier);
		if (oldest_identifier == NULL) {
			result = failure("Failed to allocate memory for the oldest container identifier.");
			verbose("Exception -> %s", last_error());

			for (size_t i = 0; i < count; i++)
				free(identifiers[i]);
			free(identifiers);

			return result;
		}
	}

	// Free the list of containers.
	for (size_t i = 0; i < count; i++)
		free(identifiers[i]);
	free(identifiers);

	verbose("The oldest container in the pool is '%s'.", oldest_identifier);

	// Set the oldest container identifier.
	*_identifier = oldest_identifier;

	return success();
}

result_t reserve_container_pool_space(const config_t* config, size_t space) {
	result_t result;

	for (;;) {
		// Get the available space in the container pool.
		size_t available_space;
		result = get_container_pool_space(&available_space, config);
		if (result != success()) {
			result = failure("Failed to reserve the container pool space due to a failure to get the available space.");
			verbose("Exception -> %s", last_error());

			return result;
		}

		// Check if the available space is sufficient.
		if (available_space >= space) {
			verbose("Successfully reserved %zu bytes in the container pool.", space);

			return success();
		}

		verbose("Insufficient space in the container pool (Wanted: %zu bytes, Available: %zu bytes). Removing the oldest container.", space, available_space);

		// Find the oldest container.
		char* oldest_identifier;
		result = find_oldest_container(&oldest_identifier, config);
		if (result != success()) {
			result = failure("Failed to reserve the container pool space due to a failure to find the oldest container.");
			verbose("Exception -> %s", last_error());

			return result;
		}

		// Check if there are no containers to remove.
		if (oldest_identifier == NULL) {
			result = failure("Insufficient space in the container pool (Wanted: %zu bytes, Available: %zu bytes), and no more containers to remove.", space, available_space);
			verbose("Exception -> %s", last_error());

			return result;
		}

		// Remove the oldest container.
		result = remove_container(config, oldest_identifier);
		if (result != success()) {
			result = failure("Failed to reserve the container pool space due to a failure to remove the oldest container.");
			verbose("Exception -> %s", last_error());

			free(oldest_identifier);

			return result;
		}

		// Free the oldest container identifier.
		free(oldest_identifier);
	}
}