#include "alloc.h"
#include "assert.h"
#include "fsEntry.h"
#include "errno.h"
#include "list.h"
#include "mem.h"

bool_t pstringSplipPath(struct pstr *path, struct pstr *upper, struct pstr *lower)
{
    typeof(path->name) curPos  = path->name;
    typeof(path->len) curLen   = path->len;
    typeof(path->len) upperLen = 0;

    // Skip leading /
    while (curLen > 0 && curPos[0] == '/') {
        curPos++;
        curLen--;
    }

    upper->name = curPos;

    // Find first non /
    while (curLen > 0 && curPos[0] != '/') {
        upperLen++;
        curLen--;
        curPos++;
    }
    upper->len = upperLen;

    while (curLen > 0 && curPos[0] == '/') {
        curPos++;
        curLen--;
    }
    lower->name = curPos;
    lower->len  = path->len - (lower->name - path->name);

    return lower->len > 0;
}

bool_t pstringIsEq(const struct pstr *p1, const struct pstr *p2)
{
    return p1->len == p2->len && (memcmp(p1->name, p2->name, p1->len) == 0);
}

bool_t pstringIsStr(const struct pstr *p, char *s)
{
    size_t slen = strlen(s);
    return p->len == slen && (memcmp(p->name, s, slen) == 0);
}

int fsEntryRef(struct fs_entry *entry)
{
    entry->ref++;
    return 0;
}

int fsEntryUnref(struct fs_entry **entry)
{
    struct fs_entry *toDelete = NULL, *entryTmp;

    entryTmp = *entry;

    while (entryTmp) {
        assert(entryTmp->ref > 0);
        entryTmp->ref--;

        if (entryTmp->ref > 0)
            break;

        if (entryTmp == *entry)
            *entry = NULL;

        if (entryTmp->parent) {
            struct fs_entry *parent = entryTmp->parent;

            assert(entryTmp->parent->ref >= 1);

            list_delete_named(parent->childs, entryTmp, prevSiblings, nextSiblings);
            // At next iteration we will decrement parent's ref cnt
        }

        // Avoid recursivity in kernel by using a list of entry to suppress
        list_add_tail_named(toDelete, entryTmp, prevSiblings, nextSiblings);

        // now, unref parent
        entryTmp = entryTmp->parent;
    }

    // free 0 ref entries
    while (!list_is_empty_named(toDelete, prevSiblings, nextSiblings)) {
        entryTmp = list_pop_head_named(toDelete, prevSiblings, nextSiblings);
        fsInodeUnref(entryTmp->node);
        free(entryTmp);
    }

    return 0;
}

struct fs_entry *fsEntryAlloc(struct fs_entry *parent, const struct pstr *name, struct inode *inode)
{
    struct fs_entry *entry = zalloc(sizeof(struct fs_entry));

    if (!entry)
        return NULL;

    if (name && name->len > 0) {
        char *allocName = malloc(name->len);

        if (!allocName) {
            free(entry);
            return NULL;
        }

        memcpy(allocName, name->name, name->len);
        entry->name.len  = name->len;
        entry->name.name = allocName;
    }

    entry->ref    = 1;
    entry->node   = inode;
    entry->parent = parent;

    fsInodeRef(inode);

    if (parent) {
        fsEntryRef(parent);
        list_add_head_named(parent->childs, entry, prevSiblings, nextSiblings);
    }

    return entry;
}

int fsEntryLookup(struct fs_entry *entry, const struct pstr *name, const struct fs_entry *root, struct fs_entry **result)
{
    if (pstringIsStr(name, ".")) {
        *result = entry;
    } else if (pstringIsStr(name, "..")) {
        if (entry == root) {
            *result = entry;
        } else {
            // If this entry is mounted, get the mountpoint
            for (; entry->mountpoint; entry = entry->mountpoint) {
                // No-op
            }

            assert(NULL != entry->parent);
            *result = entry->parent;
        }
        fsEntryRef(*result);
        return 0;
    } else {
        struct fs_entry *child;
        int childIdx;
        list_foreach_forward_named(entry->childs, child, childIdx, prevSiblings, nextSiblings)
        {
            if (pstringIsEq(&child->name, name)) {
                break;
            }
        }

        if (!list_foreach_early_break(entry->childs, child, childIdx))
            return -ENOENT;

        *result = child;
    }

    // Follow the mount chain
    for (; (*result)->mountedFs; *result = (*result)->mountedFs)
        ;

    fsEntryRef(*result);

    return 0;
}

int fsEntrySetup(void)
{
    return allocBookSlab(sizeof(struct fs_entry), PAGE_SIZE, 0, 0);
}

int fsEntryMount(struct fs_entry *mountpoint, struct fs_entry *mounted)
{
    if (mountpoint->mountedFs != NULL || mounted->mountpoint != NULL) {
        return -EBUSY;
    }

    mountpoint->mountedFs = mounted;
    mounted->mountpoint = mountpoint;

    fsEntryRef(mounted);
    fsEntryRef(mountpoint);

    return 0;
}

int fsEntryUmount(struct fs_entry *mounted)
{
    if (!mounted->mountpoint || !mounted->mountpoint->mountedFs || mounted->mountpoint->mountedFs != mounted)
        return -ENOENT;

    if (mounted->mountedFs)
        return -EBUSY;

    // self + mounted
    if (mounted->ref != 2)
        return -EBUSY;


    mounted->mountpoint->mountedFs = NULL;
    fsEntryUnref(&mounted->mountpoint);
    mounted->mountpoint = NULL;
    fsEntryUnref(&mounted);

    return 0;
}