/*

The OS agnostic file tracking API for applications
that want to interact with potentially many files on
the disk that could be changed by other applications.

Created on: 20.07.2016

*/

// TOP

#include "4tech_file_track.h"
#include "4tech_file_track_general.c"

#include <Windows.h>

typedef struct {
    OVERLAPPED overlapped;
    char result[2048];
    HANDLE dir;
    int32_t user_count;
} Win32_Directory_Listener;

typedef struct {
    DLL_Node node;
    Win32_Directory_Listener listener;
} Win32_Directory_Listener_Node;

typedef struct {
    HANDLE iocp;
    CRITICAL_SECTION table_lock;
    void *tables;
    DLL_Node free_sentinel;
} Win32_File_Track_Vars;

typedef struct {
    File_Index hash;
    HANDLE dir;
    Win32_Directory_Listener_Node *listener_node;
} Win32_File_Track_Entry;

#define to_vars(s) ((Win32_File_Track_Vars*)(s))
#define to_tables(v) ((File_Track_Tables*)(v->tables))

FILE_TRACK_LINK File_Track_Result
init_track_system(File_Track_System *system,
                  void *table_memory, int32_t table_memory_size,
                  void *listener_memory, int32_t listener_memory_size){
    File_Track_Result result = FileTrack_MemoryTooSmall;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    Assert(sizeof(Win32_File_Track_Entry) <= sizeof(File_Track_Entry));
    
    if (enough_memory_to_init_table(table_memory_size) &&
        sizeof(Win32_Directory_Listener_Node) <= listener_memory_size){
        
        // NOTE(allen): Initialize main data tables
        vars->tables = table_memory;
        File_Track_Tables *tables = to_tables(vars);
        init_table_memory(tables, table_memory_size);
        
        // NOTE(allen): Initialize nodes of directory watching
        {
            init_sentinel_node(&vars->free_sentinel);
            
            Win32_Directory_Listener_Node *listener = (Win32_Directory_Listener_Node*)listener_memory;
            int32_t count = listener_memory_size / sizeof(Win32_Directory_Listener_Node);
            for (int32_t i = 0; i < count; ++i, ++listener){
                insert_node(&vars->free_sentinel, &listener->node);
            }
        }
        
        // NOTE(allen): Prepare the file tracking synchronization objects.
        {
            InitializeCriticalSection(&vars->table_lock);
            vars->iocp = CreateIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 1);
        }
        
        result = FileTrack_Good;
    }
    
    return(result);
}

static int32_t
internal_get_parent_name(char *out, int32_t max, char *name){
    int32_t len, slash_i;
    
    char *ptr = name;
    for (; *ptr != 0; ++ptr);
    len = (int32_t)(ptr - name);
    
    // TODO(allen): make this system real
    Assert(len < max);
    
    for (slash_i = len-1;
         slash_i > 0 && name[slash_i] != '\\' && name[slash_i] != '/';
         --slash_i);
    
    for (int32_t i = 0; i < slash_i; ++i){
        out[i] = name[i];
    }
    out[slash_i] = 0;
    
    return(slash_i);
}

static File_Index
internal_get_file_index(BY_HANDLE_FILE_INFORMATION info){
    File_Index hash;
    hash.id[0] = info.nFileIndexLow;
    hash.id[1] = info.nFileIndexHigh;
    hash.id[2] = info.dwVolumeSerialNumber;
    hash.id[3] = 0;
    return(hash);
}

FILE_TRACK_LINK File_Track_Result
add_listener(File_Track_System *system, char *filename){
    File_Track_Result result = FileTrack_Good;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    EnterCriticalSection(&vars->table_lock);
    {
        File_Track_Tables *tables = to_tables(vars);
        
        // TODO(allen): make this real!
        char dir_name[1024];
        internal_get_parent_name(dir_name, sizeof(dir_name), filename);
        
        HANDLE dir = CreateFile(
            dir_name,
            FILE_LIST_DIRECTORY,
            FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
            0,
            OPEN_EXISTING,
            FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
            0);
        
        if (dir != INVALID_HANDLE_VALUE){
            BY_HANDLE_FILE_INFORMATION dir_info = {0};
            DWORD getinfo_result = GetFileInformationByHandle(dir, &dir_info);
            
            if (getinfo_result){
                File_Index dir_hash = internal_get_file_index(dir_info);
                File_Track_Entry *dir_lookup = tracking_system_lookup_entry(tables, dir_hash);
                Win32_File_Track_Entry *win32_entry = (Win32_File_Track_Entry*)dir_lookup;
                
                if (entry_is_available(dir_lookup)){
                    if (tracking_system_has_space(tables, 1)){
                        Win32_Directory_Listener_Node *node = (Win32_Directory_Listener_Node*)
                            allocate_node(&vars->free_sentinel);
                        if (node){
                            if (CreateIoCompletionPort(dir, vars->iocp, (ULONG_PTR)node, 1)){
                                ZeroStruct(node->listener.overlapped);
                                if (ReadDirectoryChangesW(dir,
                                                          node->listener.result,
                                                          sizeof(node->listener.result),
                                                          0,
                                                          FILE_NOTIFY_CHANGE_LAST_WRITE,
                                                          0,
                                                          &node->listener.overlapped,
                                                          0)){
                                    node->listener.dir = dir;
                                    node->listener.user_count = 1;
                                    
                                    win32_entry->hash = dir_hash;
                                    win32_entry->dir = dir;
                                    win32_entry->listener_node = node;
                                    ++tables->tracked_count;
                                }
                                else{
                                    result = FileTrack_FileSystemError;
                                }
                            }
                            else{
                                result = FileTrack_FileSystemError;
                            }
                            
                            if (result != FileTrack_Good){
                                insert_node(&vars->free_sentinel, &node->node);
                            }
                        }
                        else{
                            result = FileTrack_OutOfListenerMemory;
                        }
                    }
                    else{
                        result = FileTrack_OutOfTableMemory;
                    }
                }
                else{
                    Win32_Directory_Listener_Node *node = win32_entry->listener_node;
                    ++node->listener.user_count;
                }
            }
            else{
                result = FileTrack_FileSystemError;
            }
        }
        else{
            result = FileTrack_FileSystemError;
        }
        
        if (result != FileTrack_Good && dir != 0 && dir != INVALID_HANDLE_VALUE){
            CloseHandle(dir);
        }
    }
    LeaveCriticalSection(&vars->table_lock);
    
    return(result);
}

FILE_TRACK_LINK File_Track_Result
remove_listener(File_Track_System *system, char *filename){
    File_Track_Result result = FileTrack_Good;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    EnterCriticalSection(&vars->table_lock);
    
    {
        File_Track_Tables *tables = to_tables(vars);
        
        // TODO(allen): make this real!
        char dir_name[1024];
        internal_get_parent_name(dir_name, sizeof(dir_name), filename);
        
        HANDLE dir = CreateFile(
            dir_name,
            FILE_LIST_DIRECTORY,
            FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
            0,
            OPEN_EXISTING,
            FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
            0);
        
        if (dir != INVALID_HANDLE_VALUE){
            BY_HANDLE_FILE_INFORMATION dir_info = {0};
            DWORD getinfo_result = GetFileInformationByHandle(dir, &dir_info);
            
            if (getinfo_result){
                File_Index dir_hash =  internal_get_file_index(dir_info);
                File_Track_Entry *dir_lookup = tracking_system_lookup_entry(tables, dir_hash);
                Win32_File_Track_Entry *win32_dir = (Win32_File_Track_Entry*)dir_lookup;
                
                Assert(!entry_is_available(dir_lookup));
                Win32_Directory_Listener_Node *node = win32_dir->listener_node;
                --node->listener.user_count;
                
                if (node->listener.user_count == 0){
                    insert_node(&vars->free_sentinel, &node->node);
                    CloseHandle(win32_dir->dir);
                    internal_free_slot(tables, dir_lookup);
                }
            }
            else{
                result = FileTrack_FileSystemError;
            }
            
            CloseHandle(dir);
        }
        else{
            result = FileTrack_FileSystemError;
        }
    }
    
    LeaveCriticalSection(&vars->table_lock);
    
    return(result);
}

FILE_TRACK_LINK File_Track_Result
move_track_system(File_Track_System *system, void *mem, int32_t size){
    File_Track_Result result = FileTrack_Good;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    EnterCriticalSection(&vars->table_lock);
    {
        File_Track_Tables *original_tables = to_tables(vars);
        result = move_table_memory(original_tables, mem, size);
        if (result == FileTrack_Good){
            vars->tables = mem;
        }
    }
    LeaveCriticalSection(&vars->table_lock);
    
    return(result);
}

FILE_TRACK_LINK File_Track_Result
expand_track_system_listeners(File_Track_System *system, void *mem, int32_t size){
    File_Track_Result result = FileTrack_Good;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    EnterCriticalSection(&vars->table_lock);
    
    if (sizeof(Win32_Directory_Listener_Node) <= size){
        Win32_Directory_Listener_Node *listener = (Win32_Directory_Listener_Node*)mem;
        int32_t count = size / sizeof(Win32_Directory_Listener_Node);
        for (int32_t i = 0; i < count; ++i, ++listener){
            insert_node(&vars->free_sentinel, &listener->node);
        }
    }
    else{
        result = FileTrack_MemoryTooSmall;
    }
    
    LeaveCriticalSection(&vars->table_lock);
    
    return(result);
}

FILE_TRACK_LINK File_Track_Result
get_change_event(File_Track_System *system, char *buffer, int32_t max, int32_t *size){
    File_Track_Result result = FileTrack_NoMoreEvents;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    EnterCriticalSection(&vars->table_lock);
    
    {
        OVERLAPPED *overlapped = 0;
        DWORD length = 0;
        ULONG_PTR key = 0;
        
        if (GetQueuedCompletionStatus(vars->iocp,
                                      &length,
                                      &key,
                                      &overlapped,
                                      0)){
            
            Win32_Directory_Listener *listener_ptr = (Win32_Directory_Listener*)overlapped;
            
            // NOTE(allen): Get a copy of the state of this node so we can set the node
            // to work listening for changes again right away.
            Win32_Directory_Listener listener = *listener_ptr;
            
            ZeroStruct(listener_ptr->overlapped);
            ReadDirectoryChangesW(listener_ptr->dir,
                                  listener_ptr->result,
                                  sizeof(listener_ptr->result),
                                  0,
                                  FILE_NOTIFY_CHANGE_LAST_WRITE,
                                  0,
                                  &listener_ptr->overlapped,
                                  0);
            
            char *listener_buffer = listener.result;
            DWORD offset = 0;
            FILE_NOTIFY_INFORMATION *info = 0;
            
            for (;;){
                info = (FILE_NOTIFY_INFORMATION*)(listener_buffer + offset);
                
                int32_t len = info->FileNameLength / 2;
                int32_t dir_len = GetFinalPathNameByHandle(listener.dir, 0, 0,
                                                           FILE_NAME_NORMALIZED);
                int32_t req_size = dir_len + 1 + len;
                *size = req_size;
                if (req_size < max){
                    int32_t pos = 0;
                    
                    pos = GetFinalPathNameByHandle(listener.dir, buffer, max,
                                                   FILE_NAME_NORMALIZED);
                    buffer[pos++] = '\\';
                    
                    for (int32_t i = 0; i < len; ++i, ++pos){
                        buffer[pos] = (char)info->FileName[i];
                    }
                    
                    if (buffer[0] == '\\'){
                        for (int32_t i = 0; i+4 < pos; ++i){
                            buffer[i] = buffer[i+4];
                        }
                        *size -= 4;
                    }
                    
                    result = FileTrack_Good;
                }
                else{
                    // TODO(allen): Need some way to stash this result so that if the
                    // user comes back with more memory we can give them the change
                    // notification they missed.
                    result = FileTrack_MemoryTooSmall;
                }
                
                if (info->NextEntryOffset != 0){
                    // TODO(allen): We're not ready to handle this yet.
                    // For now I am breaking.  In the future, if there
                    // are more results we should stash them and return
                    // them in future calls.
                    offset += info->NextEntryOffset;
                    break;
                }
                else{
                    break;
                }
            }
        }
    }
    
    LeaveCriticalSection(&vars->table_lock);
    
    return(result);
}

FILE_TRACK_LINK File_Track_Result
shut_down_track_system(File_Track_System *system){
    File_Track_Result result = FileTrack_Good;
    Win32_File_Track_Vars *vars = to_vars(system);
    
    
    DWORD win32_result = 0;
    
    // NOTE(allen): Close all the handles stored in the table.
    {
        File_Track_Tables *tables = to_tables(vars);
        
        File_Track_Entry *entries = (File_Track_Entry*)to_ptr(tables, tables->file_table);
        uint32_t max = tables->max;
        
        for (uint32_t index = 0; index < max; ++index){
            File_Track_Entry *entry = entries + index;
            
            if (!entry_is_available(entry)){
                Win32_File_Track_Entry *win32_entry = (Win32_File_Track_Entry*)entry;
                if (!CloseHandle(win32_entry->dir)){
                    win32_result = 1;
                }
            }
        }
    }
    
    // NOTE(allen): Close all the global track system resources.
    {
        if (!CloseHandle(vars->iocp)){
            win32_result = 1;
        }
        DeleteCriticalSection(&vars->table_lock);
    }
    
    if (win32_result){
        result = FileTrack_FileSystemError;
    }
    
    return(result);
}

// BOTTOM