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

#include "cJSON_Utils.h"

static unsigned char* cJSONUtils_strdup(const unsigned char* str)
{
    size_t len = 0;
    unsigned char *copy = NULL;

    len = strlen((const char*)str) + 1;
    if (!(copy = (unsigned char*)malloc(len)))
    {
        return NULL;
    }
    memcpy(copy, str, len);

    return copy;
}

static int cJSONUtils_strcasecmp(const unsigned char *s1, const unsigned char *s2)
{
    if (!s1)
    {
        return (s1 == s2) ? 0 : 1; /* both NULL? */
    }
    if (!s2)
    {
        return 1;
    }
    for(; tolower(*s1) == tolower(*s2); ++s1, ++s2)
    {
        if(*s1 == 0)
        {
            return 0;
        }
    }

    return tolower(*s1) - tolower(*s2);
}

/* JSON Pointer implementation: */
static int cJSONUtils_Pstrcasecmp(const unsigned char *a, const unsigned char *e)
{
    if (!a || !e)
    {
        return (a == e) ? 0 : 1; /* both NULL? */
    }
    for (; *a && *e && (*e != '/'); a++, e++) /* compare until next '/' */
    {
        if (*e == '~')
        {
            /* check for escaped '~' (~0) and '/' (~1) */
            if (!((e[1] == '0') && (*a == '~')) && !((e[1] == '1') && (*a == '/')))
            {
                /* invalid escape sequence or wrong character in *a */
                return 1;
            }
            else
            {
                e++;
            }
        }
        else if (tolower(*a) != tolower(*e))
        {
            return 1;
        }
    }
    if (((*e != 0) && (*e != '/')) != (*a != 0))
    {
        /* one string has ended, the other not */
        return 1;
    }

    return 0;
}

static size_t cJSONUtils_PointerEncodedstrlen(const unsigned char *s)
{
    size_t l = 0;
    for (; *s; s++, l++)
    {
        if ((*s == '~') || (*s == '/'))
        {
            l++;
        }
    }

    return l;
}

static void cJSONUtils_PointerEncodedstrcpy(unsigned char *d, const unsigned char *s)
{
    for (; *s; s++)
    {
        if (*s == '/')
        {
            *d++ = '~';
            *d++ = '1';
        }
        else if (*s == '~')
        {
            *d++ = '~';
            *d++ = '0';
        }
        else
        {
            *d++ = *s;
        }
    }

    *d = '\0';
}

char *cJSONUtils_FindPointerFromObjectTo(cJSON *object, cJSON *target)
{
    size_t c = 0;
    cJSON *obj = 0;

    if (object == target)
    {
        /* found */
        return (char*)cJSONUtils_strdup((const unsigned char*)"");
    }

    /* recursively search all children of the object */
    for (obj = object->child; obj; obj = obj->next, c++)
    {
        unsigned char *found = (unsigned char*)cJSONUtils_FindPointerFromObjectTo(obj, target);
        if (found)
        {
            if (cJSON_IsArray(object))
            {
                /* reserve enough memory for a 64 bit integer + '/' and '\0' */
                unsigned char *ret = (unsigned char*)malloc(strlen((char*)found) + 23);
                /* check if conversion to unsigned long is valid
                 * This should be eliminated at compile time by dead code elimination
                 * if size_t is an alias of unsigned long, or if it is bigger */
                if (c > ULONG_MAX)
                {
                    free(found);
                    return NULL;
                }
                sprintf((char*)ret, "/%lu%s", (unsigned long)c, found); /* /<array_index><path> */
                free(found);

                return (char*)ret;
            }
            else if (cJSON_IsObject(object))
            {
                unsigned char *ret = (unsigned char*)malloc(strlen((char*)found) + cJSONUtils_PointerEncodedstrlen((unsigned char*)obj->string) + 2);
                *ret = '/';
                cJSONUtils_PointerEncodedstrcpy(ret + 1, (unsigned char*)obj->string);
                strcat((char*)ret, (char*)found);
                free(found);

                return (char*)ret;
            }

            /* reached leaf of the tree, found nothing */
            free(found);
            return NULL;
        }
    }

    /* not found */
    return NULL;
}

cJSON *cJSONUtils_GetPointer(cJSON *object, const char *pointer)
{
    /* follow path of the pointer */
    while ((*pointer++ == '/') && object)
    {
        if (cJSON_IsArray(object))
        {
            size_t which = 0;
            /* parse array index */
            while ((*pointer >= '0') && (*pointer <= '9'))
            {
                which = (10 * which) + (size_t)(*pointer++ - '0');
            }
            if (*pointer && (*pointer != '/'))
            {
                /* not end of string or new path token */
                return NULL;
            }
            if (which > INT_MAX)
            {
                return NULL;
            }
            object = cJSON_GetArrayItem(object, (int)which);
        }
        else if (cJSON_IsObject(object))
        {
            object = object->child;
            /* GetObjectItem. */
            while (object && cJSONUtils_Pstrcasecmp((unsigned char*)object->string, (const unsigned char*)pointer))
            {
                object = object->next;
            }
            /* skip to the next path token or end of string */
            while (*pointer && (*pointer != '/'))
            {
                pointer++;
            }
        }
        else
        {
            return NULL;
        }
    }

    return object;
}

/* JSON Patch implementation. */
static void cJSONUtils_InplaceDecodePointerString(unsigned char *string)
{
    unsigned char *s2 = string;

    if (string == NULL) {
        return;
    }

    for (; *string; s2++, string++)
    {
        *s2 = (*string != '~')
            ? (*string)
            : ((*(++string) == '0')
                    ? '~'
                    : '/');
    }

    *s2 = '\0';
}

static cJSON *cJSONUtils_PatchDetach(cJSON *object, const unsigned char *path)
{
    unsigned char *parentptr = NULL;
    unsigned char *childptr = NULL;
    cJSON *parent = NULL;
    cJSON *ret = NULL;

    /* copy path and split it in parent and child */
    parentptr = cJSONUtils_strdup(path);
    if (parentptr == NULL) {
        return NULL;
    }

    childptr = (unsigned char*)strrchr((char*)parentptr, '/'); /* last '/' */
    if (childptr == NULL)
    {
        free(parentptr);
        return NULL;
    }
    /* split strings */
    *childptr++ = '\0';

    parent = cJSONUtils_GetPointer(object, (char*)parentptr);
    cJSONUtils_InplaceDecodePointerString(childptr);

    if (!parent)
    {
        /* Couldn't find object to remove child from. */
        ret = NULL;
    }
    else if (cJSON_IsArray(parent))
    {
        ret = cJSON_DetachItemFromArray(parent, atoi((char*)childptr));
    }
    else if (cJSON_IsObject(parent))
    {
        ret = cJSON_DetachItemFromObject(parent, (char*)childptr);
    }
    free(parentptr);

    /* return the detachted item */
    return ret;
}

static int cJSONUtils_Compare(cJSON *a, cJSON *b)
{
    if ((a == NULL) || (b == NULL) || ((a->type & 0xFF) != (b->type & 0xFF)))
    {
        /* mismatched type. */
        return -1;
    }
    switch (a->type & 0xFF)
    {
        case cJSON_Number:
            /* numeric mismatch. */
            return ((a->valueint != b->valueint) || (a->valuedouble != b->valuedouble)) ? -2 : 0;
        case cJSON_String:
            /* string mismatch. */
            return (strcmp(a->valuestring, b->valuestring) != 0) ? -3 : 0;
        case cJSON_Array:
            for (a = a->child, b = b->child; a && b; a = a->next, b = b->next)
            {
                int err = cJSONUtils_Compare(a, b);
                if (err)
                {
                    return err;
                }
            }
            /* array size mismatch? (one of both children is not NULL) */
            return (a || b) ? -4 : 0;
        case cJSON_Object:
            cJSONUtils_SortObject(a);
            cJSONUtils_SortObject(b);
            a = a->child;
            b = b->child;
            while (a && b)
            {
                int err = 0;
                /* compare object keys */
                if (cJSONUtils_strcasecmp((unsigned char*)a->string, (unsigned char*)b->string))
                {
                    /* missing member */
                    return -6;
                }
                err = cJSONUtils_Compare(a, b);
                if (err)
                {
                    return err;
                }
                a = a->next;
                b = b->next;
            }
            /* object length mismatch (one of both children is not null) */
            return (a || b) ? -5 : 0;

        default:
            break;
    }
    /* null, true or false */
    return 0;
}

static int cJSONUtils_ApplyPatch(cJSON *object, cJSON *patch)
{
    cJSON *op = NULL;
    cJSON *path = NULL;
    cJSON *value = NULL;
    cJSON *parent = NULL;
    int opcode = 0;
    unsigned char *parentptr = NULL;
    unsigned char *childptr = NULL;

    op = cJSON_GetObjectItem(patch, "op");
    path = cJSON_GetObjectItem(patch, "path");
    if (!op || !path)
    {
        /* malformed patch. */
        return 2;
    }

    /* decode operation */
    if (!strcmp(op->valuestring, "add"))
    {
        opcode = 0;
    }
    else if (!strcmp(op->valuestring, "remove"))
    {
        opcode = 1;
    }
    else if (!strcmp(op->valuestring, "replace"))
    {
        opcode = 2;
    }
    else if (!strcmp(op->valuestring, "move"))
    {
        opcode = 3;
    }
    else if (!strcmp(op->valuestring, "copy"))
    {
        opcode = 4;
    }
    else if (!strcmp(op->valuestring, "test"))
    {
        /* compare value: {...} with the given path */
        return cJSONUtils_Compare(cJSONUtils_GetPointer(object, path->valuestring), cJSON_GetObjectItem(patch, "value"));
    }
    else
    {
        /* unknown opcode. */
        return 3;
    }

    /* Remove/Replace */
    if ((opcode == 1) || (opcode == 2))
    {
        /* Get rid of old. */
        cJSON_Delete(cJSONUtils_PatchDetach(object, (unsigned char*)path->valuestring));
        if (opcode == 1)
        {
            /* For Remove, this is job done. */
            return 0;
        }
    }

    /* Copy/Move uses "from". */
    if ((opcode == 3) || (opcode == 4))
    {
        cJSON *from = cJSON_GetObjectItem(patch, "from");
        if (!from)
        {
            /* missing "from" for copy/move. */
            return 4;
        }

        if (opcode == 3)
        {
            /* move */
            value = cJSONUtils_PatchDetach(object, (unsigned char*)from->valuestring);
        }
        if (opcode == 4)
        {
            /* copy */
            value = cJSONUtils_GetPointer(object, from->valuestring);
        }
        if (!value)
        {
            /* missing "from" for copy/move. */
            return 5;
        }
        if (opcode == 4)
        {
            value = cJSON_Duplicate(value, 1);
        }
        if (!value)
        {
            /* out of memory for copy/move. */
            return 6;
        }
    }
    else /* Add/Replace uses "value". */
    {
        value = cJSON_GetObjectItem(patch, "value");
        if (!value)
        {
            /* missing "value" for add/replace. */
            return 7;
        }
        value = cJSON_Duplicate(value, 1);
        if (!value)
        {
            /* out of memory for add/replace. */
            return 8;
        }
    }

    /* Now, just add "value" to "path". */

    /* split pointer in parent and child */
    parentptr = cJSONUtils_strdup((unsigned char*)path->valuestring);
    childptr = (unsigned char*)strrchr((char*)parentptr, '/');
    if (childptr)
    {
        *childptr++ = '\0';
    }
    parent = cJSONUtils_GetPointer(object, (char*)parentptr);
    cJSONUtils_InplaceDecodePointerString(childptr);

    /* add, remove, replace, move, copy, test. */
    if (!parent)
    {
        /* Couldn't find object to add to. */
        free(parentptr);
        cJSON_Delete(value);
        return 9;
    }
    else if (cJSON_IsArray(parent))
    {
        if (!strcmp((char*)childptr, "-"))
        {
            cJSON_AddItemToArray(parent, value);
        }
        else
        {
            cJSON_InsertItemInArray(parent, atoi((char*)childptr), value);
        }
    }
    else if (cJSON_IsObject(parent))
    {
        cJSON_DeleteItemFromObject(parent, (char*)childptr);
        cJSON_AddItemToObject(parent, (char*)childptr, value);
    }
    else
    {
        cJSON_Delete(value);
    }
    free(parentptr);

    return 0;
}

int cJSONUtils_ApplyPatches(cJSON *object, cJSON *patches)
{
    int err = 0;

    if (patches == NULL)
    {
        return 1;
    }

    if (cJSON_IsArray(patches))
    {
        /* malformed patches. */
        return 1;
    }
    if (patches)
    {
        patches = patches->child;
    }
    while (patches)
    {
        if ((err = cJSONUtils_ApplyPatch(object, patches)))
        {
            return err;
        }
        patches = patches->next;
    }

    return 0;
}

static void cJSONUtils_GeneratePatch(cJSON *patches, const unsigned char *op, const unsigned char *path, const unsigned char *suffix, cJSON *val)
{
    cJSON *patch = cJSON_CreateObject();
    cJSON_AddItemToObject(patch, "op", cJSON_CreateString((const char*)op));
    if (suffix)
    {
        unsigned char *newpath = (unsigned char*)malloc(strlen((const char*)path) + cJSONUtils_PointerEncodedstrlen(suffix) + 2);
        cJSONUtils_PointerEncodedstrcpy(newpath + sprintf((char*)newpath, "%s/", (const char*)path), suffix);
        cJSON_AddItemToObject(patch, "path", cJSON_CreateString((const char*)newpath));
        free(newpath);
    }
    else
    {
        cJSON_AddItemToObject(patch, "path", cJSON_CreateString((const char*)path));
    }
    if (val)
    {
        cJSON_AddItemToObject(patch, "value", cJSON_Duplicate(val, 1));
    }
    cJSON_AddItemToArray(patches, patch);
}

void cJSONUtils_AddPatchToArray(cJSON *array, const char *op, const char *path, cJSON *val)
{
    cJSONUtils_GeneratePatch(array, (const unsigned char*)op, (const unsigned char*)path, 0, val);
}

static void cJSONUtils_CompareToPatch(cJSON *patches, const unsigned char *path, cJSON *from, cJSON *to)
{
    if ((from == NULL) || (to == NULL))
    {
        return;
    }

    if ((from->type & 0xFF) != (to->type & 0xFF))
    {
        cJSONUtils_GeneratePatch(patches, (const unsigned char*)"replace", path, 0, to);
        return;
    }

    switch ((from->type & 0xFF))
    {
        case cJSON_Number:
            if ((from->valueint != to->valueint) || (from->valuedouble != to->valuedouble))
            {
                cJSONUtils_GeneratePatch(patches, (const unsigned char*)"replace", path, 0, to);
            }
            return;

        case cJSON_String:
            if (strcmp(from->valuestring, to->valuestring) != 0)
            {
                cJSONUtils_GeneratePatch(patches, (const unsigned char*)"replace", path, 0, to);
            }
            return;

        case cJSON_Array:
        {
            size_t c = 0;
            unsigned char *newpath = (unsigned char*)malloc(strlen((const char*)path) + 23); /* Allow space for 64bit int. */
            /* generate patches for all array elements that exist in "from" and "to" */
            for (c = 0, from = from->child, to = to->child; from && to; from = from->next, to = to->next, c++)
            {
                /* check if conversion to unsigned long is valid
                 * This should be eliminated at compile time by dead code elimination
                 * if size_t is an alias of unsigned long, or if it is bigger */
                if (c > ULONG_MAX)
                {
                    free(newpath);
                    return;
                }
                sprintf((char*)newpath, "%s/%lu", path, (unsigned long)c); /* path of the current array element */
                cJSONUtils_CompareToPatch(patches, newpath, from, to);
            }
            /* remove leftover elements from 'from' that are not in 'to' */
            for (; from; from = from->next, c++)
            {
                /* check if conversion to unsigned long is valid
                 * This should be eliminated at compile time by dead code elimination
                 * if size_t is an alias of unsigned long, or if it is bigger */
                if (c > ULONG_MAX)
                {
                    free(newpath);
                    return;
                }
                sprintf((char*)newpath, "%lu", (unsigned long)c);
                cJSONUtils_GeneratePatch(patches, (const unsigned char*)"remove", path, newpath, 0);
            }
            /* add new elements in 'to' that were not in 'from' */
            for (; to; to = to->next, c++)
            {
                cJSONUtils_GeneratePatch(patches, (const unsigned char*)"add", path, (const unsigned char*)"-", to);
            }
            free(newpath);
            return;
        }

        case cJSON_Object:
        {
            cJSON *a = NULL;
            cJSON *b = NULL;
            cJSONUtils_SortObject(from);
            cJSONUtils_SortObject(to);

            a = from->child;
            b = to->child;
            /* for all object values in the object with more of them */
            while (a || b)
            {
                int diff = (!a) ? 1 : ((!b) ? -1 : cJSONUtils_strcasecmp((unsigned char*)a->string, (unsigned char*)b->string));
                if (!diff)
                {
                    /* both object keys are the same */
                    unsigned char *newpath = (unsigned char*)malloc(strlen((const char*)path) + cJSONUtils_PointerEncodedstrlen((unsigned char*)a->string) + 2);
                    cJSONUtils_PointerEncodedstrcpy(newpath + sprintf((char*)newpath, "%s/", path), (unsigned char*)a->string);
                    /* create a patch for the element */
                    cJSONUtils_CompareToPatch(patches, newpath, a, b);
                    free(newpath);
                    a = a->next;
                    b = b->next;
                }
                else if (diff < 0)
                {
                    /* object element doesn't exist in 'to' --> remove it */
                    cJSONUtils_GeneratePatch(patches, (const unsigned char*)"remove", path, (unsigned char*)a->string, 0);
                    a = a->next;
                }
                else
                {
                    /* object element doesn't exist in 'from' --> add it */
                    cJSONUtils_GeneratePatch(patches, (const unsigned char*)"add", path, (unsigned char*)b->string, b);
                    b = b->next;
                }
            }
            return;
        }

        default:
            break;
    }
}

cJSON* cJSONUtils_GeneratePatches(cJSON *from, cJSON *to)
{
    cJSON *patches = cJSON_CreateArray();
    cJSONUtils_CompareToPatch(patches, (const unsigned char*)"", from, to);

    return patches;
}

/* sort lists using mergesort */
static cJSON *cJSONUtils_SortList(cJSON *list)
{
    cJSON *first = list;
    cJSON *second = list;
    cJSON *ptr = list;

    if (!list || !list->next)
    {
        /* One entry is sorted already. */
        return list;
    }

    while (ptr && ptr->next && (cJSONUtils_strcasecmp((unsigned char*)ptr->string, (unsigned char*)ptr->next->string) < 0))
    {
        /* Test for list sorted. */
        ptr = ptr->next;
    }
    if (!ptr || !ptr->next)
    {
        /* Leave sorted lists unmodified. */
        return list;
    }

    /* reset ptr to the beginning */
    ptr = list;
    while (ptr)
    {
        /* Walk two pointers to find the middle. */
        second = second->next;
        ptr = ptr->next;
        /* advances ptr two steps at a time */
        if (ptr)
        {
            ptr = ptr->next;
        }
    }
    if (second && second->prev)
    {
        /* Split the lists */
        second->prev->next = NULL;
    }

    /* Recursively sort the sub-lists. */
    first = cJSONUtils_SortList(first);
    second = cJSONUtils_SortList(second);
    list = ptr = NULL;

    while (first && second) /* Merge the sub-lists */
    {
        if (cJSONUtils_strcasecmp((unsigned char*)first->string, (unsigned char*)second->string) < 0)
        {
            if (!list)
            {
                /* start merged list with the first element of the first list */
                list = ptr = first;
            }
            else
            {
                /* add first element of first list to merged list */
                ptr->next = first;
                first->prev = ptr;
                ptr = first;
            }
            first = first->next;
        }
        else
        {
            if (!list)
            {
                /* start merged list with the first element of the second list */
                list = ptr = second;
            }
            else
            {
                /* add first element of second list to merged list */
                ptr->next = second;
                second->prev = ptr;
                ptr = second;
            }
            second = second->next;
        }
    }
    if (first)
    {
        /* Append rest of first list. */
        if (!list)
        {
            return first;
        }
        ptr->next = first;
        first->prev = ptr;
    }
    if (second)
    {
        /* Append rest of second list */
        if (!list)
        {
            return second;
        }
        ptr->next = second;
        second->prev = ptr;
    }

    return list;
}

void cJSONUtils_SortObject(cJSON *object)
{
    object->child = cJSONUtils_SortList(object->child);
}

cJSON* cJSONUtils_MergePatch(cJSON *target, cJSON *patch)
{
    if (!cJSON_IsObject(patch))
    {
        /* scalar value, array or NULL, just duplicate */
        cJSON_Delete(target);
        return cJSON_Duplicate(patch, 1);
    }

    if (!cJSON_IsObject(target))
    {
        cJSON_Delete(target);
        target = cJSON_CreateObject();
    }

    patch = patch->child;
    while (patch)
    {
        if (cJSON_IsNull(patch))
        {
            /* NULL is the indicator to remove a value, see RFC7396 */
            cJSON_DeleteItemFromObject(target, patch->string);
        }
        else
        {
            cJSON *replaceme = cJSON_DetachItemFromObject(target, patch->string);
            cJSON_AddItemToObject(target, patch->string, cJSONUtils_MergePatch(replaceme, patch));
        }
        patch = patch->next;
    }
    return target;
}

cJSON *cJSONUtils_GenerateMergePatch(cJSON *from, cJSON *to)
{
    cJSON *patch = NULL;
    if (!to)
    {
        /* patch to delete everything */
        return cJSON_CreateNull();
    }
    if (!cJSON_IsObject(to) || !cJSON_IsObject(from))
    {
        return cJSON_Duplicate(to, 1);
    }

    cJSONUtils_SortObject(from);
    cJSONUtils_SortObject(to);

    from = from->child;
    to = to->child;
    patch = cJSON_CreateObject();
    while (from || to)
    {
        int compare = from ? (to ? strcmp(from->string, to->string) : -1) : 1;
        if (compare < 0)
        {
            /* from has a value that to doesn't have -> remove */
            cJSON_AddItemToObject(patch, from->string, cJSON_CreateNull());
            from = from->next;
        }
        else if (compare > 0)
        {
            /* to has a value that from doesn't have -> add to patch */
            cJSON_AddItemToObject(patch, to->string, cJSON_Duplicate(to, 1));
            to = to->next;
        }
        else
        {
            /* object key exists in both objects */
            if (cJSONUtils_Compare(from, to))
            {
                /* not identical --> generate a patch */
                cJSON_AddItemToObject(patch, to->string, cJSONUtils_GenerateMergePatch(from, to));
            }
            /* next key in the object */
            from = from->next;
            to = to->next;
        }
    }
    if (!patch->child)
    {
        cJSON_Delete(patch);
        return NULL;
    }

    return patch;
}