//
//  GDUnixSocketServer.m
//
//  Copyright © 2016 Alexey Gordiyenko. All rights reserved.
//

/*
 The MIT License (MIT)
 
 Copyright (c) 2016 A. Gordiyenko
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */

#import "GDUnixSocketServer.h"
#import "GDUnixSocket_Private.h"

#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <string.h>

#include <sys/stat.h>

const int kGDUnixSocketServerMaxConnectionsDefault = 5;

@interface GDUnixSocketServer ()

@property (nonatomic, readonly, strong) NSLock *closeLock;
@property (nonatomic, readonly, strong) NSMutableDictionary *connectedClients;

@end

@implementation GDUnixSocketServer

#pragma mark - Public Methods

- (BOOL)listenWithError:(NSError **)error {
    return [self listenWithMaxConnections:0 error:error];
}

- (BOOL)listenWithMaxConnections:(int)maxConnections error:(NSError **)error {
    BOOL(^failureDeferBlock)(NSError *) = ^BOOL(NSError *retError) {
        if (error) {
            *error = retError;
        }
        
        return NO;
    };
    
    dispatch_fd_t socket_fd = socket(AF_UNIX, SOCK_STREAM, 0);
    [self setFd:socket_fd];
    if (socket_fd == kGDBadSocketFD) {
        return failureDeferBlock([NSError gduds_errorForCode:GDUnixSocketErrorBadSocket info:[self lastErrorInfo]]);
    }
    
    const char *socket_path = [self.socketPath cStringUsingEncoding:NSUTF8StringEncoding];
    
    struct sockaddr_un address = {};
    address.sun_family = AF_UNIX;
    strncpy(address.sun_path, socket_path, sizeof(address.sun_path) - 1);
    if (0 != strcmp(address.sun_path, socket_path)) {
        [self closeSilently];
        return failureDeferBlock([NSError gduds_errorForCode:GDUnixSocketErrorListen info:@"The socket path is inconsistent"]);
    }
    
    socket_path = address.sun_path;
    
    [self unlinkSocket:socket_path];
    
    if (0 != bind(socket_fd, (struct sockaddr *)&address, sizeof(struct sockaddr_un))) {
        [self closeSilently];
        return failureDeferBlock([NSError gduds_errorForCode:GDUnixSocketErrorBind info:[self lastErrorInfo]]);
    }
    
    if (0 != listen(socket_fd, maxConnections ?: kGDUnixSocketServerMaxConnectionsDefault)) {
        [self closeSilently];
        return failureDeferBlock([NSError gduds_errorForCode:GDUnixSocketErrorListen info:[self lastErrorInfo]]);
    }
    
    if (error) {
        *error = nil;
    }
    
    __weak typeof(self) weakSelf = self;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.001 * NSEC_PER_SEC)), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [weakSelf mainLoop];
    });
    
    self.state = GDUnixSocketStateListening;
    
    if ([self.delegate respondsToSelector:@selector(unixSocketServerDidStartListening:)]) {
        [self.delegate unixSocketServerDidStartListening:self];
    }
    
    return YES;
}

- (ssize_t)sendData:(NSData *)data toClientWithID:(NSString *)clientID error:(NSError **)error {
    @synchronized(self) {
        if (error) {
            *error = nil;
        }
        
        GDUnixSocket *client = self.connectedClients[clientID];
        if (!client) {
            if (error) {
                *error = [NSError gduds_errorForCode:GDUnixSocketErrorUnknownClient info:[NSString stringWithFormat:@"Client ID: %@", clientID]];
            }
            
            return -1;
        }
        
        return [client writeData:data error:error];
    }
}

- (void)sendData:(NSData *)data toClientWithID:(NSString *)clientID completion:(void(^)(NSError *error, ssize_t size))completion {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSError *error = nil;
        ssize_t size = [self sendData:data toClientWithID:clientID error:&error];
        if (completion) {
            completion(error, size);
        }
    });
}

#pragma mark - Overrides

- (ssize_t)writeData:(NSData *)data error:(NSError **)error {
    if (error) {
        *error = nil;
    }
    return 0;
}

- (BOOL)closeWithError:(NSError **)error {
    return [self closeWithError:error informDelegate:YES];
}

- (BOOL)closeSilently {
    return [self closeWithError:nil informDelegate:NO];
}

- (BOOL)closeWithError:(NSError **)error informDelegate:(BOOL)informDelegate {
    BOOL retVal = NO;
    // First, close all active clients.
    [self removeAllClients];
    
    // Then close the listening socket.
    [self.closeLock lock];
    NSError *retError = [self unlinkSocket];
    if (!retError) {
        retVal = [super closeWithError:&retError];
    }
    
    if (informDelegate && [self.delegate respondsToSelector:@selector(unixSocketServerDidClose:error:)]) {
        [self.delegate unixSocketServerDidClose:self error:retError];
    }
    
    [self.closeLock unlock];
    
    if (error) {
        *error = retError;
    }
    
    return retVal;
}

#pragma mark - Private Methods

- (void)readOnConnection:(GDUnixSocket *)clientConnection {
    NSError *error;
    do {
        if (![self clientExists:clientConnection]) {
            break;
        }
        
        NSData *data = [clientConnection readWithError:&error];
        if (!data) {
            if ([self clientExists:clientConnection]) {
                if (error) {
                    if ([self.delegate respondsToSelector:@selector(unixSocketServer:didFailToReadForClientID:error:)]) {
                        [self.delegate unixSocketServer:self didFailToReadForClientID:clientConnection.uniqueID error:error];
                    }
                } else {
                    if ([self.delegate respondsToSelector:@selector(unixSocketServer:clientWithIDDidDisconnect:)]) {
                        [self.delegate unixSocketServer:self clientWithIDDidDisconnect:clientConnection.uniqueID];
                    }
                }
                
                [self removeAndCloseClient:clientConnection];
            }
        } else {
            if ([self.delegate respondsToSelector:@selector(unixSocketServer:didReceiveData:fromClientWithID:)]) {
                [self.delegate unixSocketServer:self didReceiveData:data fromClientWithID:clientConnection.uniqueID];
            }
        }
    } while (!error);
}

- (void)mainLoop {
    while (true) {
        dispatch_fd_t socket_fd = [self fd];
        if (socket_fd == kGDBadSocketFD) {
            break;
        }
        
        struct sockaddr_un connection_addr = {};
        socklen_t connection_addr_len;
        dispatch_fd_t connection_fd = accept(socket_fd, (struct sockaddr *)&connection_addr, &connection_addr_len);
        if (connection_fd == kGDBadSocketFD) {
            [self.closeLock lock];
            if ([self fd] != kGDBadSocketFD) {
                // If accept failed, that means some error happened. Close listening socket.
                if ([self.delegate respondsToSelector:@selector(unixSocketServerDidFailToAcceptConnection:error:)]) {
                    NSError *error = [NSError gduds_errorForCode:GDUnixSocketErrorAccept info:[self lastErrorInfo]];
                    [self.delegate unixSocketServerDidFailToAcceptConnection:self error:error];
                }
                
                [self.closeLock unlock];
                [self close];
            } else {
                [self.closeLock unlock];
            }
            break;
        } else {
            GDUnixSocket *newConnection = [[GDUnixSocket alloc] initWithSocketPath:kGDDummySocketPath];
            [newConnection setFd:connection_fd];
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                [self readOnConnection:newConnection];
            });
            
            [self addClient:newConnection];
            
            if ([self.delegate respondsToSelector:@selector(unixSocketServer:didAcceptClientWithID:)]) {
                [self.delegate unixSocketServer:self didAcceptClientWithID:newConnection.uniqueID];
            }
        }
    }
}

- (NSError *)unlinkSocket {
    return [self unlinkSocket:[self.socketPath cStringUsingEncoding:NSUTF8StringEncoding]];
}

- (NSError *)unlinkSocket:(const char *)socketPath {
    int status;
    struct stat st;
    status = stat(socketPath, &st);
    if (status == 0) {
        // A file already exists. Check if this file is a socket node. If yes: unlink it.
        if ((st.st_mode & S_IFMT) == S_IFSOCK) {
            if (0 != unlink(socketPath)) {
                return [NSError gduds_errorForCode:GDUnixSocketErrorUnlink info:[self lastErrorInfo]];
            }
        }
    }
    
    return nil;
}

#pragma mark - Clients Related

- (void)addClient:(GDUnixSocket *)client {
    @synchronized(self) {
        if (!client) {
            [NSException raise:NSInternalInconsistencyException format:@"Cannot add empty client"];
        }
        self.connectedClients[client.uniqueID] = client;
    }
}

- (BOOL)clientExists:(GDUnixSocket *)client {
    @synchronized(self) {
        return self.connectedClients[client.uniqueID] != nil;
    }
}

- (NSError *)removeAndCloseClient:(GDUnixSocket *)client {
    if ([self clientExists:client]) {
        @synchronized(self) {
            [self.connectedClients removeObjectForKey:client.uniqueID];
            NSError *error = nil;
            [client closeWithError:&error];
            return error;
        }
    }
    
    return nil;
}

- (void)removeAllClients {
    @synchronized(self) {
        for (GDUnixSocket *client in self.connectedClients.allValues) {
            [client close];
        }
        
        [self.connectedClients removeAllObjects];
    }
}

#pragma mark - Life Cycle

- (instancetype)initWithSocketPath:(NSString *)socketPath  andFragmentSize:(size_t)fragmentSize {
    self = [super initWithSocketPath:socketPath andFragmentSize:fragmentSize];
    if (self) {
        _closeLock = [NSLock new];
        _connectedClients = [NSMutableDictionary new];
    }
    return self;
}

@end