package rados

// #cgo LDFLAGS: -lrados
// #include <stdlib.h>
// #include <rados/librados.h>
import "C"

import "unsafe"

// PoolStat represents Ceph pool statistics.
type PoolStat struct {
  // space used in bytes
  Num_bytes uint64
  // space used in KB
  Num_kb uint64
  // number of objects in the pool
  Num_objects uint64
  // number of clones of objects
  Num_object_clones uint64
  // num_objects * num_replicas
  Num_object_copies uint64
  Num_objects_missing_on_primary uint64
  // number of objects found on no OSDs
  Num_objects_unfound uint64
  // number of objects replicated fewer times than they should be
  // (but found on at least one OSD)
  Num_objects_degraded uint64
  Num_rd uint64
  Num_rd_kb uint64
  Num_wr uint64
  Num_wr_kb uint64
}

// IOContext represents a context for performing I/O within a pool.
type IOContext struct {
    ioctx C.rados_ioctx_t
}

// Write writes len(data) bytes to the object with key oid starting at byte
// offset offset. It returns an error, if any.
func (p *IOContext) Write(oid string, data []byte, offset uint64) error {
    c_oid := C.CString(oid)
    defer C.free(unsafe.Pointer(c_oid))

    ret := C.rados_write(p.ioctx, c_oid,
        (*C.char)(unsafe.Pointer(&data[0])),
        (C.size_t)(len(data)),
        (C.uint64_t)(offset))

    if ret == 0 {
        return nil
    } else {
        return RadosError(int(ret))
    }
}

// Read reads up to len(data) bytes from the object with key oid starting at byte
// offset offset. It returns the number of bytes read and an error, if any.
func (p *IOContext) Read(oid string, data []byte, offset uint64) (int, error) {
    if len(data) == 0 {
        return 0, nil
    }

    c_oid := C.CString(oid)
    defer C.free(unsafe.Pointer(c_oid))

    ret := C.rados_read(
        p.ioctx,
        c_oid,
        (*C.char)(unsafe.Pointer(&data[0])),
        (C.size_t)(len(data)),
        (C.uint64_t)(offset))

    if ret >= 0 {
        return int(ret), nil
    } else {
        return 0, RadosError(int(ret))
    }
}

// Delete deletes the object with key oid. It returns an error, if any.
func (p *IOContext) Delete(oid string) error {
    c_oid := C.CString(oid)
    defer C.free(unsafe.Pointer(c_oid))

    ret := C.rados_remove(p.ioctx, c_oid)

    if ret == 0 {
        return nil
    } else {
        return RadosError(int(ret))
    }
}

// Truncate resizes the object with key oid to size size. If the operation
// enlarges the object, the new area is logically filled with zeroes. If the
// operation shrinks the object, the excess data is removed. It returns an
// error, if any.
func (p *IOContext) Truncate(oid string, size uint64) error {
    c_oid := C.CString(oid)
    defer C.free(unsafe.Pointer(c_oid))

    ret := C.rados_trunc(p.ioctx, c_oid, (C.uint64_t)(size))

    if ret == 0 {
        return nil
    } else {
        return RadosError(int(ret))
    }
}

// Destroy informs librados that the I/O context is no longer in use.
// Resources associated with the context may not be freed immediately, and the
// context should not be used again after calling this method.
func (ioctx *IOContext) Destroy() {
    C.rados_ioctx_destroy(ioctx.ioctx)
}

// Stat returns a set of statistics about the pool associated with this I/O
// context.
func (ioctx *IOContext) GetPoolStats() (stat PoolStat, err error) {
    c_stat := C.struct_rados_pool_stat_t{}
    ret := C.rados_ioctx_pool_stat(ioctx.ioctx, &c_stat)
    if ret < 0 {
        return PoolStat{}, RadosError(int(ret))
    } else {
        return PoolStat{
            Num_bytes: uint64(c_stat.num_bytes),
            Num_kb: uint64(c_stat.num_kb),
            Num_objects: uint64(c_stat.num_objects),
            Num_object_clones: uint64(c_stat.num_object_clones),
            Num_object_copies: uint64(c_stat.num_object_copies),
            Num_objects_missing_on_primary: uint64(c_stat.num_objects_missing_on_primary),
            Num_objects_unfound: uint64(c_stat.num_objects_unfound),
            Num_objects_degraded: uint64(c_stat.num_objects_degraded),
            Num_rd: uint64(c_stat.num_rd),
            Num_rd_kb: uint64(c_stat.num_rd_kb),
            Num_wr: uint64(c_stat.num_wr),
            Num_wr_kb: uint64(c_stat.num_wr_kb),
        }, nil
    }
}

// GetPoolName returns the name of the pool associated with the I/O context.
func (ioctx *IOContext) GetPoolName() (name string, err error) {
    buf := make([]byte, 1)
    for {
        ret := C.rados_ioctx_get_pool_name(ioctx.ioctx,
            (*C.char)(unsafe.Pointer(&buf[0])), C.unsigned(len(buf)))
        if ret == -34 { // FIXME
            buf = make([]byte, len(buf)*2)
            continue
        } else if ret < 0 {
            return "", RadosError(ret)
        }
        name = C.GoStringN((*C.char)(unsafe.Pointer(&buf[0])), ret)
        return name, nil
    }
}