/*************************************************************************/
/*    Copyright (C) 2015 Wizardry and Steamworks - License: GNU GPLv3    */
/*************************************************************************/
/*                                                                       */
/*  breadthTraversal                                                     */
/*                                                                       */
/*  Traverses a directory path breadth-first starting from an initial    */
/*  user-supplied path.                                                  */
/*                                                                       */
/*  This program uses a queue implementation for Amiga OS found at:      */
/*  http://grimore.org/amiga/development/data_structures/queues/strings  */
/*                                                                       */
/*  Amiga OS using SAS/C and issuing: sc link breadthTraversal.c         */
/*                                                                       */
/*************************************************************************/
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <setjmp.h>

#include <proto/exec.h>
#include <proto/dos.h>

/*************************************************************************/
/*          Wizardry and Steamworks' string queue implementation.        */
/*************************************************************************/

/* The stringQueue structure with front being the index of the front-mode
 * element and rear being the index of the last element in the queue
 */
typedef struct {
    ULONG size;
    UBYTE **store;
    ULONG front, rear;
} stringQueue;
 
/*
 * Creates a new stringQueue with a given size.
 */
stringQueue* stringQueueCreate(ULONG size) {
    stringQueue *q = (stringQueue*)AllocMem(
        sizeof(stringQueue), 
        MEMF_ANY|MEMF_CLEAR
    );
    if ((q->store = 
        (UBYTE**)AllocMem(
            size * sizeof(UBYTE **), 
            MEMF_ANY|MEMF_CLEAR
        )) == NULL) return NULL;
    q->size = size;
    q->front = 0;
    q->rear = 0;
    return q;
}
 
/*
 * Takes as parameter a stringQueue and returns 1 if the queue is empty or 
 * 0 if the queue is not empty.
 */
BOOL stringQueueIsEmpty(stringQueue *q) {
    return (BOOL)(q->rear == q->front);
}
 
/*
 * Enqueues an element to the stringQueue.
 */
void stringQueueEnqueue(stringQueue *q, UBYTE *e) {
    UBYTE **qStore;
    if (q->rear > q->size - 1) { // realloc for AmigaOS
        qStore = (UBYTE **)AllocMem(
            (q->size + 1) * sizeof(UBYTE **), 
            MEMF_ANY|MEMF_CLEAR
        );
        CopyMem(q->store, qStore, q->size * sizeof(UBYTE **));
        FreeMem(q->store, sizeof(q->store));
        q->store = qStore;
        ++q->size;
    }
    q->store[q->rear] = (UBYTE*)AllocMem(
        strlen(e) * sizeof(UBYTE *) + 1, 
        MEMF_ANY|MEMF_CLEAR
    );
    CopyMem(e, q->store[q->rear], strlen(e) * sizeof(UBYTE *) + 1);
    ++q->rear;
}
 
/*
 * Dequeues an element from the stringQueue or returns NULL in case the
 * queue is empty.
 */
UBYTE *stringQueueDequeue(stringQueue *q) {
    UBYTE *e;
    if (stringQueueIsEmpty(q))
        return NULL;
    e = (UBYTE *)AllocMem(
        strlen(q->store[q->front]) * sizeof(UBYTE *) + 1, 
        MEMF_ANY|MEMF_CLEAR
    );
    CopyMem(
        q->store[q->front], 
        e, 
        strlen(q->store[q->front]) * sizeof(UBYTE *) + 1
    );
    ++q->front;
    return e;
}
 
/*
 * Prints out the elements of the stringQueue.
 */
void stringQueuePrint(stringQueue *q) {
    ULONG i;
    if (stringQueueIsEmpty(q)) {
        Printf("Queue is empty.\n");
        return;
    }
    Printf("Elements in the queue: ");
    i = q->front;
    do {
        Printf("%s ", q->store[i]);
    } while (++i < q->rear);
    Printf("\n");
}

/*************************************************************************/
/*        Version string used for querying the program version.          */
/*************************************************************************/
GLOBAL TEXT version_string[] = 
  "\0$VER: breadthTraversal 1.0 (29 Jul 2015) by Wizardry and Steamworks";

/*************************************************************************/
/*              Amiga OS command-line arguments parameters.              */
/*************************************************************************/
STATIC CONST TEXT template[] = "PATH/A";
enum {
    PATH,
    NUM_ARGS
};

/*************************************************************************/
/*    Traverses a queue of paths and prints out files and directories.   */
/*************************************************************************/
LONG TraversePath(stringQueue *dirQueue) {
    struct FileInfoBlock *FIB = NULL;
    UBYTE *path;
    BPTR lock = NULL;
    UBYTE *nextPath;
    ULONG nextSize;
    jmp_buf env;
    LONG error;
    
    /* jump: Free any resources before returning an error. */
    error = setjmp(env);
    if(error != 0) {
        /* Free the file information block. */
        if(FIB != NULL) FreeDosObject(DOS_FIB, FIB);
        /* Release the lock. */
        if(lock != NULL) UnLock(lock);
        /* And return the error. */
        return error;
    }
    
    /* The directory queue is empty so return. */
    if(stringQueueIsEmpty(dirQueue))
        return 0;
    
    /* Dequeue the first lined-up element in the queue. */
    path = stringQueueDequeue(dirQueue);
    
    /* Lock the path. */
    if((lock = Lock(path, ACCESS_READ)) == NULL) {
        Printf("Unable to acquire a read lock to the specified path.\n");
        longjmp(env, RETURN_ERROR);
    }

    /* Create a new file information block to scan the path. */
    if((FIB = (struct FileInfoBlock *)
        AllocDosObject(DOS_FIB, NULL)) == NULL) {
        Printf("Unable to allocate file information block.\n");
        longjmp(env, RETURN_ERROR);
    }
    
    if(Examine(lock, FIB)) {
        /* Examine the rest of the entries in the directory. */
        while(ExNext(lock, FIB)) {
            /* check for Ctrl-C */
            if(CheckSignal(SIGBREAKF_CTRL_C) != FALSE)
                longjmp(env, RETURN_WARN);
            nextSize = strlen(path) + 
                strlen(FIB->fib_FileName) * 
                sizeof(UBYTE *) + 1;
            if((nextPath = (UBYTE*)
                AllocMem(nextSize, MEMF_ANY|MEMF_CLEAR)) == NULL) {
                Printf("Unable to allocate memory for path.\n");
                longjmp(env, RETURN_ERROR);
            }
            CopyMem(path, nextPath, nextSize);
            if(AddPart(nextPath, FIB->fib_FileName, nextSize) == FALSE) {
                Printf("Unable to add the file to the path.\n");
                longjmp(env, RETURN_ERROR);
            }
            /* Check whether the path is a file or a directory. */
            switch(FIB->fib_DirEntryType > 0) {
                case TRUE: // We have a directory.
                    Printf("Dirs: %s\n", nextPath);
                    
                    // So we enqueue it.
                    stringQueueEnqueue(dirQueue, nextPath);
                    
                    break;
                default: // We have a file.
                    Printf("File: %s\n", nextPath);
                    break;
            }
        }
    }

    /* Free the file information block. */
    if(FIB != NULL) FreeDosObject(DOS_FIB, FIB);

    /* Release the lock. */
    if(lock != NULL) UnLock(lock);
    
    /* DEBUG: print the queue. */
    /* stringQueuePrint(dirQueue); */
    
    /* Recurse over the queue till it is empty. */
    return TraversePath(dirQueue);
}

/*************************************************************************/
/*                          Program entry.                               */
/*************************************************************************/
int main(int argc, char **argv) {
    stringQueue *dirQueue = NULL;
    struct FileInfoBlock *FIB = NULL;
    BPTR lock = NULL;
    LONG size;
    jmp_buf env;
    LONG error;
    
    /* Setup command-line arguments to retrieve path.*/
    LONG *arg_array;
    struct RDArgs *rdargs;
    UBYTE *path;
    
    /* jump: Free any resources before returning an error. */
    error = setjmp(env);
    if(error != 0) {
        /* Free the file information block. */
        if(FIB != NULL) FreeDosObject(DOS_FIB, FIB);
        /* Release the lock. */
        if(lock != NULL) UnLock(lock);
        /* And return the error. */
        return error;
    }
 
    /* Allocate memory for arg array. */
    if((arg_array = AllocMem(NUM_ARGS, MEMF_ANY|MEMF_CLEAR)) == NULL) {
        Printf("Unable to allocate memory for command-line arguments.\n");
        longjmp(env, RETURN_ERROR);
    }
 
    /* Read command-line arguments */
    if((rdargs = ReadArgs(template, arg_array, NULL)) == NULL) {
        FreeArgs(rdargs);
        longjmp(env, RETURN_ERROR);
    }
    /* Allocate memory for the path name as the product between the lengh 
     * of the path name and the size of UBYTE plus a termination character. 
     */
    size = strlen((STRPTR)arg_array[PATH]) * sizeof(UBYTE) + 1;
    /* Allocate memory for path name. */
    if((path = AllocMem(size, MEMF_ANY|MEMF_CLEAR)) == NULL) {
        Printf("Unable to allocate memory for path name.\n");
        longjmp(env, RETURN_ERROR);
    }
    /* Copy path name to be able to free the command-line arguments. */
    CopyMem((STRPTR)arg_array[PATH], path, size);
    FreeArgs(rdargs);
    
    Printf("Specified path: %s\n", path);
    
    /* Lock the path. */
    if((lock = Lock(path, ACCESS_READ)) == NULL) {
        Printf("Unable to acquire a read lock to the specified path.\n");
        longjmp(env, RETURN_ERROR);
    }
    
    /* Create a new file information block to scan the path. */
    if((FIB = (struct FileInfoBlock *)
        AllocDosObject(DOS_FIB, NULL)) == NULL) {
        Printf("Unable to allocate file information block.\n");
        longjmp(env, RETURN_ERROR);
    }
    
    /* Attempt to examine the path. */
    if(!Examine(lock, FIB)) {
        Printf("Unable to examine %s\n", path);
        longjmp(env, RETURN_ERROR);
    }
    
    /* If the specified path is a file bail out. */
    if(FIB->fib_DirEntryType < 0) {
        Printf("Specified path is a file.\n");
        longjmp(env, RETURN_ERROR);
    }
    
    /* Free the file information block. */
    if(FIB != NULL) FreeDosObject(DOS_FIB, FIB);

    /* Release the lock. */
    if(lock != NULL) UnLock(lock);
    
    /* Allocate a new queue. */
    dirQueue = stringQueueCreate(1);
    /* Enqueue the specified path. */
    stringQueueEnqueue(dirQueue, path);
    
    /* Now traverse the path and return any errors. */
    return TraversePath(dirQueue);
}