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    extern crate bit_vec;
    extern crate byteorder;
    extern crate crc;
    extern crate libc;
    extern crate libz_sys;
    extern crate miniz_sys;
    extern crate num_cpus;
    extern crate scoped_pool;

    use scoped_pool::Pool;
    use std::collections::{HashMap, HashSet};
    use std::fs::{File, copy};
    use std::io::{BufWriter, Write, stderr, stdout};
    use std::path::{Path, PathBuf};
    use std::sync::{Arc, Mutex};

    pub mod deflate {
        pub mod deflate;
        pub mod libz_stream;
        pub mod miniz_stream;
    }
    pub mod png;

    #[derive(Clone,Debug)]
    /// Options controlling the output of the `optimize` function
    pub struct Options {
        /// Whether the input file should be backed up before writing the output
        /// Default: `false`
        pub backup: bool,
        /// Path to write the output file to
        pub out_file: PathBuf,
        /// Used only in CLI interface
        pub out_dir: Option<PathBuf>,
        /// Write to stdout instead of a file
        /// Default: `false`
        pub stdout: bool,
        /// Attempt to fix errors when decoding the input file rather than returning an `Err`
        /// Default: `false`
        pub fix_errors: bool,
        /// Don't actually write any output, just calculate the best results
        /// Default: `false`
        pub pretend: bool,
        /// Used only in CLI interface
        pub recursive: bool,
        /// Overwrite existing output files
        /// Default: `true`
        pub clobber: bool,
        /// Create new output files if they don't exist
        /// Default: `true`
        pub create: bool,
        /// Write to output even if there was no improvement in compression
        /// Default: `false`
        pub force: bool,
        /// Ensure the output file has the same permissions as the input file
        /// Default: `false`
        pub preserve_attrs: bool,
        /// How verbose the console logging should be (`None` for quiet, `Some(0)` for normal, `Some(1)` for verbose)
        /// Default: `Some(0)`
        pub verbosity: Option<u8>,
        /// Which filters to try on the file (0-5)
        /// Default: `0,5`
        pub filter: HashSet<u8>,
        /// Whether to change the interlacing type of the file
        /// `None` will not change the current interlacing type
        /// `Some(x)` will change the file to interlacing mode `x`
        /// Default: `None`
        pub interlace: Option<u8>,
        /// Which zlib compression levels to try on the file (1-9)
        /// Default: `9`
        pub compression: HashSet<u8>,
        /// Which zlib memory levels to try on the file (1-9)
        /// Default: `9`
        pub memory: HashSet<u8>,
        /// Which zlib compression strategies to try on the file (0-3)
        /// Default: `0-3`
        pub strategies: HashSet<u8>,
        /// Window size to use when compressing the file, as `2^window` bytes
        /// Doesn't affect compression but may affect speed and memory usage
        /// 8-15 are valid values
        /// Default: `15`
        pub window: u8,
        /// Whether to attempt bit depth reduction
        /// Default: `true`
        pub bit_depth_reduction: bool,
        /// Whether to attempt color type reduction
        /// Default: `true`
        pub color_type_reduction: bool,
        /// Whether to attempt palette reduction
        /// Default: `true`
        pub palette_reduction: bool,
        /// Whether to perform IDAT recoding
        /// If any type of reduction is performed, IDAT recoding will be performed
        /// regardless of this setting
        /// Default: `true`
        pub idat_recoding: bool,
        /// Which headers to strip from the PNG file, if any
        /// Default: `None`
        pub strip: png::Headers,
        /// Whether to use heuristics to pick the best filter and compression
        /// Intended for use with `-o 1` from the CLI interface
        /// Default: `false`
        pub use_heuristics: bool,
        /// Number of threads to use
        /// Default: 1.5x CPU cores, rounded down
        pub threads: usize,
    }

    impl Default for Options {
        fn default() -> Options {
            // Default settings based on -o 2 from the CLI interface
            let mut filter = HashSet::new();
            filter.insert(0);
            filter.insert(5);
            let mut compression = HashSet::new();
            compression.insert(9);
            let mut memory = HashSet::new();
            memory.insert(9);
            let mut strategies = HashSet::new();
            for i in 0..4 {
                strategies.insert(i);
            }

            // Default to 1 thread on single-core, otherwise use threads = 1.5x CPU cores
            let num_cpus = num_cpus::get();
            let thread_count = num_cpus + (num_cpus >> 1);

            Options {
                backup: false,
                out_file: PathBuf::new(),
                out_dir: None,
                stdout: false,
                pretend: false,
                recursive: false,
                fix_errors: false,
                clobber: true,
                create: true,
                force: false,
                preserve_attrs: false,
                verbosity: Some(0),
                filter: filter,
                interlace: None,
                compression: compression,
                memory: memory,
                strategies: strategies,
                window: 15,
                bit_depth_reduction: true,
                color_type_reduction: true,
                palette_reduction: true,
                idat_recoding: true,
                strip: png::Headers::None,
                use_heuristics: false,
                threads: thread_count,
            }
        }
    }

    /// Perform optimization on the input file using the options provided
    pub fn optimize(filepath: &Path, opts: &Options) -> Result<(), String> {
        // Read in the file and try to decode as PNG.
        if opts.verbosity.is_some() {
            writeln!(&mut stderr(), "Processing: {}", filepath.to_str().unwrap()).ok();
        }

        let in_file = Path::new(filepath);
        let original_size = in_file.metadata().unwrap().len() as usize;
        let mut png = match png::PngData::new(&in_file, opts.fix_errors) {
            Ok(x) => x,
            Err(x) => return Err(x),
        };

        // Run the optimizer on the decoded PNG.
        let optimized_output = optimize_png(&mut png, original_size, opts);

        if is_fully_optimized(original_size, optimized_output.len(), opts) {
            writeln!(&mut stderr(), "File already optimized").ok();
            return Ok(());
        }

        if opts.pretend {
            if opts.verbosity.is_some() {
                writeln!(&mut stderr(), "Running in pretend mode, no output").ok();
            }
        } else {
            if opts.backup {
                match copy(in_file,
                           in_file.with_extension(format!("bak.{}",
                                                          in_file.extension()
                                                                 .unwrap()
                                                                 .to_str()
                                                                 .unwrap()))) {
                    Ok(x) => x,
                    Err(_) => {
                        return Err(format!("Unable to write to backup file at {}",
                                           opts.out_file.display()))
                    }
                };
            }

            if opts.stdout {
                let mut buffer = BufWriter::new(stdout());
                match buffer.write_all(&optimized_output) {
                    Ok(_) => (),
                    Err(_) => return Err("Unable to write to stdout".to_owned()),
                }
            } else {
                let out_file = match File::create(&opts.out_file) {
                    Ok(x) => x,
                    Err(_) => {
                        return Err(format!("Unable to write to file {}", opts.out_file.display()))
                    }
                };

                if opts.preserve_attrs {
                    match File::open(filepath) {
                        Ok(f) => {
                            match f.metadata() {
                                Ok(metadata) => {
                                    // TODO: Implement full permission changing on Unix
                                    // Not available in stable, requires block cfg statements
                                    // See https://github.com/rust-lang/rust/issues/15701
                                    {
                                        match out_file.metadata() {
                                            Ok(out_meta) => {
                                                let readonly = metadata.permissions()
                                                                       .readonly();
                                                out_meta.permissions()
                                                        .set_readonly(readonly);
                                            }
                                            Err(_) => {
                                                if opts.verbosity.is_some() {
                                                    writeln!(&mut stderr(),
                                                             "Failed to set permissions on output file")
                                                        .ok();
                                                }
                                            }
                                        }
                                    }
                                }
                                Err(_) => {
                                    if opts.verbosity.is_some() {
                                        writeln!(&mut stderr(),
                                                 "Failed to read permissions on input file")
                                            .ok();
                                    }
                                }
                            }
                        }
                        Err(_) => {
                            if opts.verbosity.is_some() {
                                writeln!(&mut stderr(), "Failed to read permissions on input file")
                                    .ok();
                            }
                        }
                    };
                }

                let mut buffer = BufWriter::new(out_file);
                match buffer.write_all(&optimized_output) {
                    Ok(_) => {
                        if opts.verbosity.is_some() {
                            writeln!(&mut stderr(), "Output: {}", opts.out_file.display()).ok();
                        }
                    }
                    Err(_) => {
                        return Err(format!("Unable to write to file {}", opts.out_file.display()))
                    }
                }
            }
        }
        Ok(())
    }

    /// Perform optimization on the input file using the options provided, where the file is already
    /// loaded in-memory
    pub fn optimize_from_memory(data: &[u8], opts: &Options) -> Result<Vec<u8>, String> {
        // Read in the file and try to decode as PNG.
        if opts.verbosity.is_some() {
            writeln!(&mut stderr(), "Processing from memory").ok();
        }
        let original_size = data.len() as usize;
        let mut png = match png::PngData::from_slice(&data, opts.fix_errors) {
            Ok(x) => x,
            Err(x) => return Err(x),
        };

        // Run the optimizer on the decoded PNG.
        let optimized_output = optimize_png(&mut png, original_size, opts);

        if is_fully_optimized(original_size, optimized_output.len(), opts) {
            writeln!(&mut stderr(), "Image already optimized").ok();
            Ok(data.to_vec())
        } else {
            Ok(optimized_output)
        }
    }

    /// Perform optimization on the input PNG object using the options provided
    fn optimize_png(mut png: &mut png::PngData, file_original_size: usize, opts: &Options) -> Vec<u8> {
        type TrialWithData = (u8, u8, u8, u8, Vec<u8>);

        // Print png info
        let idat_original_size = png.idat_data.len();
        if opts.verbosity.is_some() {
            writeln!(&mut stderr(),
                     "    {}x{} pixels, PNG format",
                     png.ihdr_data.width,
                     png.ihdr_data.height)
                .ok();
            if let Some(palette) = png.palette.clone() {
                writeln!(&mut stderr(),
                         "    {} bits/pixel, {} colors in palette",
                         png.ihdr_data.bit_depth,
                         palette.len() / 3)
                    .ok();
            } else {
                writeln!(&mut stderr(),
                         "    {}x{} bits/pixel, {:?}",
                         png.channels_per_pixel(),
                         png.ihdr_data.bit_depth,
                         png.ihdr_data.color_type)
                    .ok();
            }
            writeln!(&mut stderr(),
                     "    IDAT size = {} bytes",
                     idat_original_size)
                .ok();
            writeln!(&mut stderr(),
                     "    File size = {} bytes",
                     file_original_size)
                .ok();
        }

        let mut filter = opts.filter.clone();
        let compression = opts.compression.clone();
        let memory = opts.memory.clone();
        let mut strategies = opts.strategies.clone();

        if opts.use_heuristics {
            // Heuristically determine which set of options to use
            if png.ihdr_data.bit_depth.as_u8() >= 8 &&
               png.ihdr_data.color_type != png::ColorType::Indexed {
                if filter.is_empty() {
                    filter.insert(5);
                }
                if strategies.is_empty() {
                    strategies.insert(1);
                }
            } else {
                if filter.is_empty() {
                    filter.insert(0);
                }
                if strategies.is_empty() {
                    strategies.insert(0);
                }
            }
        }

        let something_changed = perform_reductions(&mut png, &opts);

        if opts.idat_recoding || something_changed {
            let thread_count = opts.threads;
            let pool = Pool::new(thread_count);
            // Go through selected permutations and determine the best
            let best: Arc<Mutex<Option<TrialWithData>>> = Arc::new(Mutex::new(None));
            let combinations = filter.len() * compression.len() * memory.len() * strategies.len();
            let mut results: Vec<(u8, u8, u8, u8)> = Vec::with_capacity(combinations);
            let mut filters: HashMap<u8, Vec<u8>> = HashMap::with_capacity(filter.len());
            if opts.verbosity.is_some() {
                writeln!(&mut stderr(), "Trying: {} combinations", combinations).ok();
            }

            for f in &filter {
                let filtered = png.filter_image(*f);
                filters.insert(*f, filtered.clone());
                for zc in &compression {
                    for zm in &memory {
                        for zs in &strategies {
                            results.push((*f, *zc, *zm, *zs));
                        }
                    }
                }
            }
            pool.scoped(|scope| {
                let original_len = png.idat_data.len();
                let interlacing_changed = opts.interlace.is_some() &&
                                          opts.interlace != Some(png.ihdr_data.interlaced);
                for trial in &results {
                    let filtered = filters.get(&trial.0).unwrap();
                    let best = best.clone();
                    scope.execute(move || {
                        let new_idat = deflate::deflate::deflate(filtered,
                                                                 trial.1,
                                                                 trial.2,
                                                                 trial.3,
                                                                 opts.window)
                                           .unwrap();

                        if opts.verbosity == Some(1) {
                            writeln!(&mut stderr(),
                                     "    zc = {}  zm = {}  zs = {}  f = {}        {} bytes",
                                     trial.1,
                                     trial.2,
                                     trial.3,
                                     trial.0,
                                     new_idat.len())
                                .ok();
                        }

                        let mut best = best.lock().unwrap();
                        if (best.is_some() &&
                            new_idat.len() < best.as_ref().map(|x| x.4.len()).unwrap()) ||
                           (best.is_none() &&
                            (new_idat.len() < original_len || interlacing_changed || opts.force)) {
                            *best = Some((trial.0, trial.1, trial.2, trial.3, new_idat));
                        }
                    });
                }
            });

            let mut final_best = best.lock().unwrap();
            if let Some(better) = final_best.take() {
                png.idat_data = better.4.clone();
                if opts.verbosity.is_some() {
                    writeln!(&mut stderr(), "Found better combination:").ok();
                    writeln!(&mut stderr(),
                             "    zc = {}  zm = {}  zs = {}  f = {}        {} bytes",
                             better.1,
                             better.2,
                             better.3,
                             better.0,
                             png.idat_data.len())
                        .ok();
                }
            }
        }

        perform_strip(&mut png, &opts);

        let output = png.output();

        if opts.verbosity.is_some() {
            if idat_original_size >= png.idat_data.len() {
                writeln!(&mut stderr(),
                         "    IDAT size = {} bytes ({} bytes decrease)",
                         png.idat_data.len(),
                         idat_original_size - png.idat_data.len())
                    .ok();
            } else {
                writeln!(&mut stderr(),
                         "    IDAT size = {} bytes ({} bytes increase)",
                         png.idat_data.len(),
                         png.idat_data.len() - idat_original_size)
                    .ok();
            }
            if file_original_size >= output.len() {
                writeln!(&mut stderr(),
                         "    file size = {} bytes ({} bytes = {:.2}% decrease)",
                         output.len(),
                         file_original_size - output.len(),
                         (file_original_size - output.len()) as f64 / file_original_size as f64 *
                         100f64)
                    .ok();
            } else {
                writeln!(&mut stderr(),
                         "    file size = {} bytes ({} bytes = {:.2}% increase)",
                         output.len(),
                         output.len() - file_original_size,
                         (output.len() - file_original_size) as f64 / file_original_size as f64 *
                         100f64)
                    .ok();
            }
        }

        output
    }

    /// Attempt all reduction operations requested by the given `Options` struct
    /// and apply them directly to the `PngData` passed in
    fn perform_reductions(png: &mut png::PngData, opts: &Options) -> bool {
        let mut something_changed = false;

        if opts.palette_reduction {
            if png.reduce_palette() {
                something_changed = true;
                if opts.verbosity == Some(1) {
                    report_reduction(&png);
                }
            };
        }

        if opts.bit_depth_reduction {
            if png.reduce_bit_depth() {
                something_changed = true;
                if opts.verbosity == Some(1) {
                    report_reduction(&png);
                }
            };
        }

        if opts.color_type_reduction {
            if png.reduce_color_type() {
                something_changed = true;
                if opts.verbosity == Some(1) {
                    report_reduction(&png);
                }
            };
        }

        if something_changed && opts.verbosity.is_some() {
            report_reduction(&png);
        }

        if let Some(interlacing) = opts.interlace {
            if png.change_interlacing(interlacing) {
                png.ihdr_data.interlaced = interlacing;
                something_changed = true;
            }
        }

        something_changed
    }

    /// Display the status of the image data after a reduction has taken place
    fn report_reduction(png: &png::PngData) {
        if let Some(palette) = png.palette.clone() {
            writeln!(&mut stderr(),
                     "Reducing image to {} bits/pixel, {} colors in palette",
                     png.ihdr_data.bit_depth,
                     palette.len() / 3)
                .ok();
        } else {
            writeln!(&mut stderr(),
                     "Reducing image to {}x{} bits/pixel, {}",
                     png.channels_per_pixel(),
                     png.ihdr_data.bit_depth,
                     png.ihdr_data.color_type)
                .ok();
        }
    }

    /// Strip headers from the `PngData` object, as requested by the passed `Options`
    fn perform_strip(png: &mut png::PngData, opts: &Options) {
        match opts.strip.clone() {
            // Strip headers
            png::Headers::None => (),
            png::Headers::Some(hdrs) => {
                for hdr in &hdrs {
                    png.aux_headers.remove(hdr);
                }
            }
            png::Headers::Safe => {
                const PRESERVED_HEADERS: [&'static str; 9] = ["cHRM", "gAMA", "iCCP", "sBIT", "sRGB",
                                                              "bKGD", "hIST", "pHYs", "sPLT"];
                let mut preserved = HashMap::new();
                for (hdr, contents) in &png.aux_headers {
                    if PRESERVED_HEADERS.contains(&hdr.as_ref()) {
                        preserved.insert(hdr.clone(), contents.clone());
                    }
                }
                png.aux_headers = preserved;
            }
            png::Headers::All => {
                png.aux_headers = HashMap::new();
            }
        }
    }

    /// Check if an image was already optimized prior to oxipng's operations
    fn is_fully_optimized(original_size: usize, optimized_size: usize, opts: &Options) -> bool {
        original_size <= optimized_size && !opts.force && opts.interlace.is_none()
    }

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