src/server/plugins/postgresql/vfs.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2022 Olaf Wintermann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "vfs.h"

#include <inttypes.h>

#include "../../util/util.h"

static VFS pg_vfs_class = {
    pg_vfs_open,
    pg_vfs_stat,
    pg_vfs_fstat,
    pg_vfs_opendir,
    pg_vfs_fdopendir,
    pg_vfs_mkdir,
    pg_vfs_unlink,
    pg_vfs_rmdir
};

static VFS_IO pg_vfs_io_class = {
    pg_vfs_io_read,
    pg_vfs_io_write,
    pg_vfs_io_pread,
    pg_vfs_io_pwrite,
    pg_vfs_io_seek,
    pg_vfs_io_close,
    NULL, // no pg aio implementation yet
    NULL
};

static VFS_DIRIO pg_vfs_dirio_class = {
    pg_vfs_dirio_readdir,
    pg_vfs_dirio_close
};


/*
 * SQL Queries
 */

// Resolves a path into resource_id and parent_id
// params: $1: path string
static const char *sql_resolve_path = 
    "with recursive resolvepath as (\n\
        select\n\
            resource_id,\n\
            parent_id,\n\
            iscollection,\n\
            regexp_split_to_array($1, '/') as pathelm,\n\
            '' as fullpath,\n\
            1 as pathdepth\n\
        from Resource\n\
        where parent_id is null\n\
        union\n\
        select\n\
            r.resource_id,\n\
            r.parent_id,\n\
            r.iscollection,\n\
            p.pathelm,\n\
            p.fullpath || '/' || r.nodename,\n\
            p.pathdepth + 1\n\
        from Resource r\n\
        inner join resolvepath p on r.parent_id = p.resource_id\n\
        where p.pathelm[p.pathdepth+1] = r.nodename\n\
    )\n\
    select resource_id, parent_id, fullpath, iscollection from resolvepath\n\
    where fullpath = $1 ;";

// Same as sql_resolve_path, but it returns the root collection
// params: $1: path string (should be '/')
static const char *sql_get_root = "select resource_id, parent_id, $1 as fullpath, true as iscollection from Resource where parent_id is null;";

// Get all children of a specific collection
// params: $1: parent resource_id
static const char *sql_get_children = "select resource_id, nodename, iscollection from Resource where parent_id = $1;";


VFS* pg_vfs_create(Session *sn, Request *rq, pblock *pb) {
    // resourcepool is required
    char *resource_pool = pblock_findval("resourcepool", pb);
    if(!resource_pool) {
        log_ereport(LOG_MISCONFIG, "pg_vfs_create: missing resourcepool parameter");
        return NULL;
    }
    
    // get the resource first (most likely to fail due to misconfig)
    ResourceData *resdata = resourcepool_lookup(sn, rq, resource_pool, 0);
    if(!resdata) {
        log_ereport(LOG_MISCONFIG, "postgresql vfs: resource pool %s not found", resource_pool);
        return NULL;
    }
    // resdata will be freed automatically when the request is finished
    
    // Create a new VFS object and a separate instance object
    // VFS contains fptrs that can be copied from pg_vfs_class
    // instance contains request specific data (PGconn)
    VFS *vfs = pool_malloc(sn->pool, sizeof(VFS));
    if(!vfs) {
        return NULL;
    }
    
    PgVFS *vfs_priv = pool_malloc(sn->pool, sizeof(PgVFS));
    if(!vfs_priv) {
        pool_free(sn->pool, vfs);
        return NULL;
    }
    vfs_priv->connection = resdata->data;
    vfs_priv->pg_resource = resdata;
    
    memcpy(vfs, &pg_vfs_class, sizeof(VFS));
    vfs->flags = 0;
    vfs->instance = vfs_priv;
    
    return vfs;
}


int pg_resolve_path(VFSContext *ctx, const char *path, int64_t *parent_id, int64_t *resource_id, const char **resource_name, WSBool *iscollection) {
    // basic path validation
    if(!path) return 1;
    size_t pathlen = strlen(path);
    if(pathlen == 0) return 1;
    if(path[0] != '/') {
        return 1;
    }
    
    // get last node of path
    *resource_name = util_resource_name(path);
    
    VFS *vfs = ctx->vfs;
    PgVFS *pg = vfs->instance;
    
    const char *sql = pathlen == 1 ? sql_get_root : sql_resolve_path;
    PGresult *result = PQexecParams(
            pg->connection,
            sql,
            1,     // number of parameters
            NULL,
            &path, // parameter value
            NULL,
            NULL,
            0);    // 0: result in text format
    
    if(!result) return 1;
    
    int ret = 1;
    int nfields = PQnfields(result);
    int nrows = PQntuples(result);
    if(nrows == 1 && nfields == 4) {
        char *resource_id_str = PQgetvalue(result, 0, 0);
        char *parent_id_str = PQgetvalue(result, 0, 1);
        char *iscol = PQgetvalue(result, 0, 3);
        if(resource_id_str && parent_id_str) {
            if(util_strtoint(resource_id_str, resource_id)) {
                ret = 0; // success
            }
            // optionally get parent_id
            util_strtoint(parent_id_str, parent_id);
        }
        if(iscol) {
            *iscollection = iscol[0] == 't' ? TRUE : FALSE;
        }
    } else {
        ctx->vfs_errno = ENOENT;
    }
    
    PQclear(result);
    
    return ret;
}


/* -------------------------- VFS functions -------------------------- */

SYS_FILE pg_vfs_open(VFSContext *ctx, const char *path, int oflags) {
    const char *resname;
    int64_t resource_id, parent_id;
    resource_id = -1;
    parent_id = -1;
    WSBool iscollection;
    if(pg_resolve_path(ctx, path, &parent_id, &resource_id, &resname, &iscollection)) {
        return NULL;
    }
    
    VFSFile *file = pool_malloc(ctx->pool, sizeof(VFSFile));
    if(!file) {
        return NULL;
    }
    PgFile *pgfile = pool_malloc(ctx->pool, sizeof(PgFile));
    if(!pgfile) {
        pool_free(ctx->pool, file);
        return NULL;
    }
    
    pgfile->iscollection = iscollection;
    pgfile->resource_id = resource_id;
    pgfile->parent_id = parent_id;
    
    file->ctx = ctx;
    file->io = iscollection ? NULL : &pg_vfs_io_class;
    file->fd = -1;
    file->data = pgfile;
    
    return file;
}

int pg_vfs_stat(VFSContext *ctx, const char *path, struct stat *buf) {
    
}

int pg_vfs_fstat(VFSContext *ctx, SYS_FILE fd, struct stat *buf) {
    
}

VFS_DIR pg_vfs_opendir(VFSContext *ctx, const char *path) {
    VFSFile *file = pg_vfs_open(ctx, path, O_RDONLY);
    if(!file) return NULL;
    return pg_vfs_fdopendir(ctx, file);
}

VFS_DIR pg_vfs_fdopendir(VFSContext *ctx, SYS_FILE fd) {
    PgFile *pg = fd->data;
    if(!pg->iscollection) {
        ctx->vfs_errno = ENOTDIR;
        return NULL;
    }
    
    VFSDir *dir = pool_malloc(ctx->pool, sizeof(VFSDir));
    if(!dir) {
        fd->io->close(fd);
        ctx->vfs_errno = ENOMEM;
        return NULL;
    }
    
    PgDir *pgdir = pool_malloc(ctx->pool, sizeof(PgDir));
    if(!pgdir) {
        fd->io->close(fd);
        pool_free(ctx->pool, dir);
        ctx->vfs_errno = ENOMEM;
        return NULL;
    }
    memset(pgdir, 0, sizeof(PgDir));
    pgdir->file = fd;
    
    dir->ctx = ctx;
    dir->io = &pg_vfs_dirio_class;
    dir->data = pgdir;
    dir->fd = -1;
    
    return dir;
}

int pg_vfs_mkdir(VFSContext *ctx, const char *path) {
    
}

int pg_vfs_unlink(VFSContext *ctx, const char *path) {
    
}

int pg_vfs_rmdir(VFSContext *Ctx, const char *path) {
    
}


/* -------------------------- VFS_IO functions -------------------------- */

ssize_t pg_vfs_io_read(SYS_FILE fd, void *buf, size_t nbyte) {
    
}

ssize_t pg_vfs_io_write(SYS_FILE fd, const void *buf, size_t nbyte) {
    
}

ssize_t pg_vfs_io_pread(SYS_FILE fd, void *buf, size_t nbyte, off_t offset) {
    
}

ssize_t pg_vfs_io_pwrite(SYS_FILE fd, const void *buf, size_t nbyte, off_t offset) {
    
}

off_t pg_vfs_io_seek(SYS_FILE fd, off_t offset, int whence) {
    
}

void pg_vfs_io_close(SYS_FILE fd) {
    
}


/* -------------------------- VFS_DIRIO functions -------------------------- */

static int load_dir(VFSDir *dir, PgDir *pg) {
    VFS *vfs = dir->ctx->vfs;
    PgVFS *pgvfs = vfs->instance;
    PgFile *pgfd = pg->file->data;
    PgDir *pgdir = dir->data;
    
    char resid_param[32];
    snprintf(resid_param, 32, "%" PRId64, pgfd->resource_id);
    
    const char *param = resid_param;
    
    PGresult *result = PQexecParams(
            pgvfs->connection,
            sql_get_children,
            1,                                  // number of parameters
            NULL,
            &param,  // param: parent resource_id 
            NULL,
            NULL,
            0);                                 // 0: result in text format
    if(!result) return 1;
    
    pgdir->result = result;
    pgdir->nrows = PQntuples(result);
    return 0;
}

int pg_vfs_dirio_readdir(VFS_DIR dir, VFS_ENTRY *entry, int getstat) {
    PgDir *pg = dir->data;
    if(!pg->result) {
        if(load_dir(dir, pg)) {
            return 0;
        }
    }
    
    if(pg->row >= pg->nrows) {
        return 0; // EOF
    }
    
    entry->name = PQgetvalue(pg->result, pg->row, 1);
        
    // TODO: stat

    pg->row++;
    return 1;
}

void pg_vfs_dirio_close(VFS_DIR dir) {
    pool_handle_t *pool = dir->ctx->pool;
    PgDir *pg = dir->data;
    if(pg->result) {
        PQclear(pg->result);
    }
    PgFile *pgfile = pg->file->data;
    
    pool_free(pool, pgfile);
    pool_free(pool, pg->file);
    pool_free(pool, pg);
    pool_free(pool, dir);
}