//!Multipart support

use bytes::Bytes;
use mime::Mime;
use mime_guess;

use std::path;
use std::fs;
use std::io;
use std::io::Write;

use crate::header::{ContentDisposition, Filename};
use crate::utils::BytesWriter;

const DEFAULT_BOUNDARY: &'static str = "yuki";

///Multipart Form.
///
///Default boundary is `yuki`.
pub struct Form {
    ///Boundary to use.
    pub boundary: &'static str,
    storage: BytesWriter,
}

impl Form {
    ///Creates new instance of form.
    pub fn new() -> Self {
        Self::with_boundary(DEFAULT_BOUNDARY)
    }

    ///Creates new instance with provided boundary.
    ///
    ///# Panic
    ///
    ///In debug builds, it asserts whether string contains only ASCII characters or not.
    pub fn with_boundary(boundary: &'static str) -> Self {
        debug_assert!(boundary.is_ascii());

        Self {
            boundary,
            storage: BytesWriter::new()
        }
    }

    ///Adds new field with jsut name.
    pub fn add_field(&mut self, name: String, data: &[u8]) {
        let content_disposition = ContentDisposition::FormData(Some(name), Filename::new());
        let _ = write!(&mut self.storage, "--{}\r\nContent-Disposition: {}\r\n\r\n", self.boundary, content_disposition);
        let _ = self.storage.write(data);
        let _ = write!(&mut self.storage, "\r\n--{}\r\n", self.boundary);
    }

    ///Adds new field with file.
    pub fn add_file_field(&mut self, field_name: String, file_name: String, mime: &Mime, data: &[u8]) {
        let content_disposition = ContentDisposition::FormData(Some(field_name), Filename::with_name(file_name));
        let _ = write!(&mut self.storage, "--{}\r\nContent-Disposition: {}\r\n", self.boundary, content_disposition);
        let _ = write!(&mut self.storage, "Content-Type: {}\r\n\r\n", mime);
        let _ = self.storage.write(data);
        let _ = write!(&mut self.storage, "\r\n--{}\r\n", self.boundary);
    }

    ///Adds file to the form.
    ///
    ///# Note
    ///
    ///It reads entire file into buffer.
    ///
    ///# IO Error
    ///
    ///If error happens file copying content of file,
    ///then content of storage shall be restored to its state
    ///before starting the operation.
    pub fn add_file<P: AsRef<path::Path>>(&mut self, field_name: String, path: P) -> io::Result<()> {
        let original_len = self.storage.len();

        let path = path.as_ref();

        let mut file = fs::File::open(&path)?;
        let file_name = match path.file_name().and_then(|file_name| file_name.to_str()) {
            Some(file_name) => Filename::with_name(file_name.to_string()),
            None => Filename::new(),
        };
        let file_meta = file.metadata()?;
        let file_len = file_meta.len() as usize;
        let mime = mime_guess::from_path(path).first_or_octet_stream();

        let content_disposition = ContentDisposition::FormData(Some(field_name), file_name);
        let _ = write!(&mut self.storage, "--{}\r\nContent-Disposition: {}\r\n", self.boundary, content_disposition);
        let _ = write!(&mut self.storage, "Content-Type: {}\r\n\r\n", mime);

        self.storage.reserve(file_len);
        //If error happens we must clean up
        if let Err(error) = io::copy(&mut file, &mut self.storage) {
            self.storage.split_off(original_len);
            return Err(error);
        }

        let _ = write!(&mut self.storage, "\r\n--{}\r\n", self.boundary);

        Ok(())
    }

    ///Finishes creating form and produces body with its length
    pub fn finish(self) -> (u64, Bytes) {
        let mut bytes = self.storage.into_inner();
        let len = bytes.len();
        if len == 0 {
            return (0, bytes.freeze());
        }

        bytes[len-2] = 45; //'-'
        bytes[len-1] = 45;

        bytes.extend_from_slice("\r\n".as_bytes());
        let len = len as u64 + 2;

        (len, bytes.freeze())
    }
}

#[cfg(test)]
mod tests {
    use super::Form;
    use mime::TEXT_PLAIN;
    use std::{fs, str};
    use std::io::Read;

    #[test]
    fn multipart_form_add_simple_field() {
        const EXPECTED: &'static str = "--yuki\r\nContent-Disposition: form-data; name=\"SimpleField\"\r\n\r\nsimple test\r\n--yuki--\r\n";

        let mut form = Form::new();
        form.add_field("SimpleField".to_string(), "simple test".as_bytes());

        let (len, body) = form.finish();
        let str_body = str::from_utf8(&body).expect("To get str slice of body");
        assert_eq!(len, EXPECTED.len() as u64);
        assert_eq!(str_body, EXPECTED);
    }

    #[test]
    fn multipart_form_add_file() {
        const FILE_NAME: &'static str = "Cargo.toml";

        let mut file_body = String::new();
        let mut file = fs::File::open(FILE_NAME).expect("to open file");
        file.read_to_string(&mut file_body).expect("Read to string");
        let expected = format!("--yuki\r\nContent-Disposition: form-data; name=\"Cargo\"; filename=\"Cargo.toml\"\r\nContent-Type: text/x-toml\r\n\r\n{}\r\n--yuki--\r\n", file_body);

        let mut form = Form::new();
        form.add_file("Cargo".to_string(), FILE_NAME).expect("To read file");

        let (len, body) = form.finish();
        let str_body = str::from_utf8(&body).expect("To get str slice of body");
        assert_eq!(len as usize, expected.len());
        assert_eq!(str_body, expected);
    }


    #[test]
    fn multipart_form_add_multiple_fields() {
        const EXPECTED: &'static str = "--yuki\r\nContent-Disposition: form-data; name=\"SimpleField\"\r\n\r\nsimple test\r\n--yuki\r\n--yuki\r\nContent-Disposition: form-data; name=\"SimpleFile\"; filename=\"File.txt\"\r\nContent-Type: text/plain\r\n\r\nsimple file\r\n--yuki--\r\n";

        let mut form = Form::new();
        form.add_field("SimpleField".to_string(), "simple test".as_bytes());
        form.add_file_field("SimpleFile".to_string(), "File.txt".to_string(), &TEXT_PLAIN, "simple file".as_bytes());

        let (len, body) = form.finish();
        let str_body = str::from_utf8(&body).expect("To get str slice of body");
        assert_eq!(len, EXPECTED.len() as u64);
        assert_eq!(str_body, EXPECTED);
    }

}