use std::ffi::CStr;
use std::ptr;
use std::borrow::Cow;
use std::fmt;
use std::slice;
use libc::c_void;

use mongoc::bindings;
use bson;

use super::Result;

pub struct Bsonc {
    inner: *mut bindings::bson_t
}

impl Bsonc {
    pub fn new() -> Bsonc {
        Bsonc::from_ptr(unsafe { bindings::bson_new() })
    }

    pub fn from_ptr(inner: *const bindings::bson_t) -> Bsonc {
        assert!(!inner.is_null());
        Bsonc { inner: inner as *mut bindings::bson_t }
    }

    pub fn from_document(document: &bson::Document) -> Result<Bsonc> {
        let mut buffer = Vec::new();
        try!(bson::encode_document(&mut buffer, document));

        let inner = unsafe {
            bindings::bson_new_from_data(
                buffer[..].as_ptr(),
                buffer.len() as u64
            )
        };

        // Inner will be null if there was an error converting the data.
        // We're assuming the bson crate works and therefore assert here.
        // See: http://api.mongodb.org/libbson/current/bson_new_from_data.html
        assert!(!inner.is_null());

        Ok(Bsonc{ inner: inner })
    }

    pub fn as_document(&self) -> Result<bson::Document> {
        assert!(!self.inner.is_null());

        // This pointer should not be modified or freed
        // See: http://api.mongodb.org/libbson/current/bson_get_data.html
        let data_ptr = unsafe { bindings::bson_get_data(self.inner) };
        assert!(!data_ptr.is_null());

        let data_len = unsafe {
            let bson = *self.inner;
            bson.len
        } as usize;

        let mut slice = unsafe {
            slice::from_raw_parts(data_ptr, data_len)
        };

        let document = try!(bson::decode_document(&mut slice));
        Ok(document)
    }

    pub fn as_json(&self) -> Cow<str> {
        assert!(!self.inner.is_null());
        let json_ptr = unsafe { bindings::bson_as_json(self.inner, ptr::null_mut()) };
        assert!(!json_ptr.is_null());
        let json_cstr = unsafe { CStr::from_ptr(json_ptr) };
        let out = String::from_utf8_lossy(json_cstr.to_bytes());
        unsafe { bindings::bson_free(json_ptr as *mut c_void); }
        out
    }

    pub fn inner(&self) -> *const bindings::bson_t {
        assert!(!self.inner.is_null());
        self.inner
    }

    pub fn mut_inner(&mut self) -> *mut bindings::bson_t {
        assert!(!self.inner.is_null());
        self.inner as *mut bindings::bson_t
    }
}

impl fmt::Debug for Bsonc {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Bsonc: {}", self.as_json())
    }
}

impl Drop for Bsonc {
    fn drop(&mut self) {
        unsafe {
            bindings::bson_destroy(self.inner);
        }
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_bsonc_from_and_as_document() {
        let document = doc! { "key" => "value" };
        let bsonc = super::Bsonc::from_document(&document).unwrap();

        let decoded = bsonc.as_document().unwrap();
        assert!(decoded.contains_key("key"));
    }

    #[test]
    fn test_bsonc_from_and_as_json() {
        let document = doc! { "key" => "value" };
        let bsonc = super::Bsonc::from_document(&document).unwrap();
        assert_eq!("{ \"key\" : \"value\" }", bsonc.as_json());
    }
}