use std::ffi::OsStr;
use std::fmt;

use log::*;

use dns::{QClass, find_qtype_number, qtype};
use dns::record::{A, find_other_qtype_number};

use crate::connect::TransportType;
use crate::output::{OutputFormat, UseColours, TextFormat};
use crate::requests::{RequestGenerator, Inputs, ProtocolTweaks, UseEDNS};
use crate::resolve::Resolver;
use crate::txid::TxidGenerator;


/// The command-line options used when running dog.
#[derive(PartialEq, Debug)]
pub struct Options {

    /// The requests to make and how they should be generated.
    pub requests: RequestGenerator,

    /// Whether to display the time taken after every query.
    pub measure_time: bool,

    /// How to format the output data.
    pub format: OutputFormat,
}

impl Options {

    /// Parses and interprets a set of options from the user’s command-line
    /// arguments.
    ///
    /// This returns an `Ok` set of options if successful and running
    /// normally, a `Help` or `Version` variant if one of those options is
    /// specified, or an error variant if there’s an invalid option or
    /// inconsistency within the options after they were parsed.
    #[allow(unused_results)]
    pub fn getopts<C>(args: C) -> OptionsResult
    where C: IntoIterator,
          C::Item: AsRef<OsStr>,
    {
        let mut opts = getopts::Options::new();

        // Query options
        opts.optmulti("q", "query",       "Host name or IP address to query", "HOST");
        opts.optmulti("t", "type",        "Type of the DNS record being queried (A, MX, NS...)", "TYPE");
        opts.optmulti("n", "nameserver",  "Address of the nameserver to send packets to", "ADDR");
        opts.optmulti("",  "class",       "Network class of the DNS record being queried (IN, CH, HS)", "CLASS");

        // Sending options
        opts.optopt ("",  "edns",         "Whether to OPT in to EDNS (disable, hide, show)", "SETTING");
        opts.optopt ("",  "txid",         "Set the transaction ID to a specific value", "NUMBER");
        opts.optopt ("Z", "",             "Uncommon protocol tweaks", "TWEAKS");

        // Protocol options
        opts.optflag("U", "udp",          "Use the DNS protocol over UDP");
        opts.optflag("T", "tcp",          "Use the DNS protocol over TCP");
        opts.optflag("S", "tls",          "Use the DNS-over-TLS protocol");
        opts.optflag("H", "https",        "Use the DNS-over-HTTPS protocol");

        // Output options
        opts.optopt ("",  "color",        "When to use terminal colors",  "WHEN");
        opts.optopt ("",  "colour",       "When to use terminal colours", "WHEN");
        opts.optflag("J", "json",         "Display the output as JSON");
        opts.optflag("",  "seconds",      "Do not format durations, display them as seconds");
        opts.optflag("1", "short",        "Short mode: display nothing but the first result");
        opts.optflag("",  "time",         "Print how long the response took to arrive");

        // Meta options
        opts.optflag("v", "version",      "Print version information");
        opts.optflag("?", "help",         "Print list of command-line options");

        let matches = match opts.parse(args) {
            Ok(m)  => m,
            Err(e) => return OptionsResult::InvalidOptionsFormat(e),
        };

        let uc = UseColours::deduce(&matches);

        if matches.opt_present("version") {
            OptionsResult::Version(uc)
        }
        else if matches.opt_present("help") {
            OptionsResult::Help(HelpReason::Flag, uc)
        }
        else {
            match Self::deduce(matches) {
                Ok(opts) => {
                    if opts.requests.inputs.domains.is_empty() {
                        OptionsResult::Help(HelpReason::NoDomains, uc)
                    }
                    else {
                        OptionsResult::Ok(opts)
                    }
                }
                Err(e) => {
                    OptionsResult::InvalidOptions(e)
                }
            }
        }
    }

    fn deduce(matches: getopts::Matches) -> Result<Self, OptionsError> {
        let measure_time = matches.opt_present("time");
        let format = OutputFormat::deduce(&matches);
        let requests = RequestGenerator::deduce(matches)?;

        Ok(Self { requests, measure_time, format })
    }
}


impl RequestGenerator {
    fn deduce(matches: getopts::Matches) -> Result<Self, OptionsError> {
        let edns = UseEDNS::deduce(&matches)?;
        let txid_generator = TxidGenerator::deduce(&matches)?;
        let protocol_tweaks = ProtocolTweaks::deduce(&matches)?;
        let inputs = Inputs::deduce(matches)?;

        Ok(Self { inputs, txid_generator, edns, protocol_tweaks })
    }
}


impl Inputs {
    fn deduce(matches: getopts::Matches) -> Result<Self, OptionsError> {
        let mut inputs = Self::default();
        inputs.load_transport_types(&matches);
        inputs.load_named_args(&matches)?;
        inputs.load_free_args(matches)?;
        inputs.load_fallbacks();
        Ok(inputs)
    }

    fn load_transport_types(&mut self, matches: &getopts::Matches) {
        if matches.opt_present("https") {
            self.transport_types.push(TransportType::HTTPS);
        }

        if matches.opt_present("tls") {
            self.transport_types.push(TransportType::TLS);
        }

        if matches.opt_present("tcp") {
            self.transport_types.push(TransportType::TCP);
        }

        if matches.opt_present("udp") {
            self.transport_types.push(TransportType::UDP);
        }
    }

    fn load_named_args(&mut self, matches: &getopts::Matches) -> Result<(), OptionsError> {
        for domain in matches.opt_strs("query") {
            self.domains.push(domain);
        }

        for qtype in matches.opt_strs("type") {
            self.add_type(&qtype)?;
        }

        for ns in matches.opt_strs("nameserver") {
            self.add_nameserver(&ns)?;
        }

        for qclass in matches.opt_strs("class") {
            self.add_class(&qclass)?;
        }

        Ok(())
    }

    fn add_type(&mut self, input: &str) -> Result<(), OptionsError> {
        if input == "OPT" {
            return Err(OptionsError::QueryTypeOPT);
        }

        let type_number = find_qtype_number(input)
            .or_else(|| find_other_qtype_number(input))
            .or_else(|| input.parse().ok());

        match type_number {
            Some(qtype)  => Ok(self.types.push(qtype)),
            None         => Err(OptionsError::InvalidQueryType(input.into())),
        }
    }

    fn add_nameserver(&mut self, input: &str) -> Result<(), OptionsError> {
        self.resolvers.push(Resolver::Specified(input.into()));
        Ok(())
    }

    fn parse_class_name(&self, input: &str) -> Option<QClass> {
        match input {
            "IN"  => Some(QClass::IN),
            "CH"  => Some(QClass::CH),
            "HS"  => Some(QClass::HS),
            _     => None,
        }
    }

    fn add_class(&mut self, input: &str) -> Result<(), OptionsError> {
        let qclass = self.parse_class_name(input)
            .or_else(|| input.parse().ok().map(QClass::Other));

        match qclass {
            Some(class)  => Ok(self.classes.push(class)),
            None         => Err(OptionsError::InvalidQueryClass(input.into())),
        }
    }

    fn load_free_args(&mut self, matches: getopts::Matches) -> Result<(), OptionsError> {
        for a in matches.free {
            if a.starts_with('@') {
                trace!("Got nameserver -> {:?}", &a[1..]);
                self.add_nameserver(&a[1..])?;
            }
            else if a.chars().all(char::is_uppercase) {
                if let Some(class) = self.parse_class_name(&a) {
                    trace!("Got qclass -> {:?}", &a);
                    self.classes.push(class);
                }
                else {
                    trace!("Got qtype -> {:?}", &a);
                    self.add_type(&a)?;
                }
            }
            else {
                trace!("Got domain -> {:?}", &a);
                self.domains.push(a);
            }
        }

        Ok(())
    }

    fn load_fallbacks(&mut self) {
        if self.types.is_empty() {
            self.types.push(qtype!(A));
        }

        if self.classes.is_empty() {
            self.classes.push(QClass::IN);
        }

        if self.resolvers.is_empty() {
            self.resolvers.push(Resolver::SystemDefault);
        }

        if self.transport_types.is_empty() {
            self.transport_types.push(TransportType::Automatic);
        }
    }
}


impl TxidGenerator {
    fn deduce(matches: &getopts::Matches) -> Result<Self, OptionsError> {
        if let Some(starting_txid) = matches.opt_str("txid") {
            if let Some(start) = parse_dec_or_hex(&starting_txid) {
                Ok(Self::Sequence(start))
            }
            else {
                Err(OptionsError::InvalidTxid(starting_txid))
            }
        }
        else {
            Ok(Self::Random)
        }
    }
}

fn parse_dec_or_hex(input: &str) -> Option<u16> {
    if input.starts_with("0x") {
        match u16::from_str_radix(&input[2..], 16) {
            Ok(num) => {
                Some(num)
            }
            Err(e) => {
                warn!("Error parsing hex number: {}", e);
                None
            }
        }
    }
    else {
        match input.parse() {
            Ok(num) => {
                Some(num)
            }
            Err(e) => {
                warn!("Error parsing number: {}", e);
                None
            }
        }
    }
}


impl OutputFormat {
    fn deduce(matches: &getopts::Matches) -> Self {
        if matches.opt_present("short") {
            let summary_format = TextFormat::deduce(matches);
            Self::Short(summary_format)
        }
        else if matches.opt_present("json") {
            Self::JSON
        }
        else {
            let use_colours = UseColours::deduce(matches);
            let summary_format = TextFormat::deduce(matches);
            Self::Text(use_colours, summary_format)
        }
    }
}


impl UseColours {
    fn deduce(matches: &getopts::Matches) -> Self {
        match matches.opt_str("color").or_else(|| matches.opt_str("colour")).unwrap_or_default().as_str() {
            "automatic" | "auto" | ""  => Self::Automatic,
            "always"    | "yes"        => Self::Always,
            "never"     | "no"         => Self::Never,
            otherwise => {
                warn!("Unknown colour setting {:?}", otherwise);
                Self::Automatic
            },
        }
    }
}


impl TextFormat {
    fn deduce(matches: &getopts::Matches) -> Self {
        let format_durations = ! matches.opt_present("seconds");
        Self { format_durations }
    }
}


impl UseEDNS {
    fn deduce(matches: &getopts::Matches) -> Result<Self, OptionsError> {
        if let Some(edns) = matches.opt_str("edns") {
            match edns.as_str() {
                "disable" | "off"  => Ok(Self::Disable),
                "hide"             => Ok(Self::SendAndHide),
                "show"             => Ok(Self::SendAndShow),
                oh                 => Err(OptionsError::InvalidEDNS(oh.into())),
            }
        }
        else {
            Ok(Self::SendAndHide)
        }
    }
}


impl ProtocolTweaks {
    fn deduce(matches: &getopts::Matches) -> Result<Self, OptionsError> {
        let mut tweaks = Self::default();

        if let Some(tweak_strs) = matches.opt_str("Z") {
            for tweak_str in tweak_strs.split(',') {
                match &*tweak_str {
                    "authentic"  => { tweaks.set_authentic_flag = true; },
                    otherwise    => return Err(OptionsError::InvalidTweak(otherwise.into())),
                }
            }
        }

        Ok(tweaks)
    }
}


/// The result of the `Options::getopts` function.
#[derive(PartialEq, Debug)]
pub enum OptionsResult {

    /// The options were parsed successfully.
    Ok(Options),

    /// There was an error (from `getopts`) parsing the arguments.
    InvalidOptionsFormat(getopts::Fail),

    /// There was an error with the combination of options the user selected.
    InvalidOptions(OptionsError),

    /// Can’t run any checks because there’s help to display!
    Help(HelpReason, UseColours),

    /// One of the arguments was `--version`, to display the version number.
    Version(UseColours),
}

/// The reason that help is being displayed. If it’s for the `--help` flag,
/// then we shouldn’t return an error exit status.
#[derive(PartialEq, Debug, Copy, Clone)]
pub enum HelpReason {

    /// Help was requested with the `--help` flag.
    Flag,

    /// There were no domains being queried, so display help instead.
    /// Unlike `dig`, we don’t implicitly search for the root domain.
    NoDomains,
}

/// Something wrong with the combination of options the user has picked.
#[derive(PartialEq, Debug)]
pub enum OptionsError {
    TooManyProtocols,
    InvalidEDNS(String),
    InvalidQueryType(String),
    InvalidQueryClass(String),
    InvalidTxid(String),
    InvalidTweak(String),
    QueryTypeOPT,
}

impl fmt::Display for OptionsError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::TooManyProtocols       => write!(f, "Too many protocols"),
            Self::InvalidEDNS(edns)      => write!(f, "Invalid EDNS setting {:?}", edns),
            Self::InvalidQueryType(qt)   => write!(f, "Invalid query type {:?}", qt),
            Self::InvalidQueryClass(qc)  => write!(f, "Invalid query class {:?}", qc),
            Self::InvalidTxid(txid)      => write!(f, "Invalid transaction ID {:?}", txid),
            Self::InvalidTweak(tweak)    => write!(f, "Invalid protocol tweak {:?}", tweak),
            Self::QueryTypeOPT           => write!(f, "OPT request is sent by default (see -Z flag)"),
        }
    }
}


#[cfg(test)]
mod test {
    use super::*;
    use pretty_assertions::assert_eq;
    use dns::record::*;

    impl Inputs {
        fn fallbacks() -> Self {
            Inputs {
                domains:         vec![ /* No domains by default */ ],
                types:           vec![ qtype!(A) ],
                classes:         vec![ QClass::IN ],
                resolvers:       vec![ Resolver::SystemDefault ],
                transport_types: vec![ TransportType::Automatic ],
            }
        }
    }

    impl OptionsResult {
        fn unwrap(self) -> Options {
            match self {
                Self::Ok(o)  => o,
                _            => panic!("{:?}", self),
            }
        }
    }

    // help tests

    #[test]
    fn help() {
        assert_eq!(Options::getopts(&[ "--help" ]),
                   OptionsResult::Help(HelpReason::Flag, UseColours::Automatic));
    }

    #[test]
    fn help_no_colour() {
        assert_eq!(Options::getopts(&[ "--help", "--colour=never" ]),
                   OptionsResult::Help(HelpReason::Flag, UseColours::Never));
    }

    #[test]
    fn version() {
        assert_eq!(Options::getopts(&[ "--version" ]),
                   OptionsResult::Version(UseColours::Automatic));
    }

    #[test]
    fn version_yes_color() {
        assert_eq!(Options::getopts(&[ "--version", "--color", "always" ]),
                   OptionsResult::Version(UseColours::Always));
    }

    #[test]
    fn fail() {
        assert_eq!(Options::getopts(&[ "--pear" ]),
                   OptionsResult::InvalidOptionsFormat(getopts::Fail::UnrecognizedOption("pear".into())));
    }

    #[test]
    fn empty() {
        let nothing: Vec<&str> = vec![];
        assert_eq!(Options::getopts(nothing),
                   OptionsResult::Help(HelpReason::NoDomains, UseColours::Automatic));
    }

    #[test]
    fn an_unrelated_argument() {
        assert_eq!(Options::getopts(&[ "--time" ]),
                   OptionsResult::Help(HelpReason::NoDomains, UseColours::Automatic));
    }

    // query tests

    #[test]
    fn just_domain() {
        let options = Options::getopts(&[ "lookup.dog" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn just_named_domain() {
        let options = Options::getopts(&[ "-q", "lookup.dog" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn domain_and_type() {
        let options = Options::getopts(&[ "lookup.dog", "SOA" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            types:      vec![ qtype!(SOA) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn domain_and_nameserver() {
        let options = Options::getopts(&[ "lookup.dog", "@1.1.1.1" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            resolvers:  vec![ Resolver::Specified("1.1.1.1".into()) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn domain_and_class() {
        let options = Options::getopts(&[ "lookup.dog", "CH" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            classes:    vec![ QClass::CH ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn all_free() {
        let options = Options::getopts(&[ "lookup.dog", "CH", "NS", "@1.1.1.1" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            classes:    vec![ QClass::CH ],
            types:      vec![ qtype!(NS) ],
            resolvers:  vec![ Resolver::Specified("1.1.1.1".into()) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn all_parameters() {
        let options = Options::getopts(&[ "-q", "lookup.dog", "--class", "CH", "--type", "SOA", "--nameserver", "1.1.1.1" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            classes:    vec![ QClass::CH ],
            types:      vec![ qtype!(SOA) ],
            resolvers:  vec![ Resolver::Specified("1.1.1.1".into()) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn two_types() {
        let options = Options::getopts(&[ "-q", "lookup.dog", "--type", "SRV", "--type", "AAAA" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            types:      vec![ qtype!(SRV), qtype!(AAAA) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn two_classes() {
        let options = Options::getopts(&[ "-q", "lookup.dog", "--class", "IN", "--class", "CH" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            classes:    vec![ QClass::IN, QClass::CH ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn all_mixed_1() {
        let options = Options::getopts(&[ "lookup.dog", "--class", "CH", "SOA", "--nameserver", "1.1.1.1" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            classes:    vec![ QClass::CH ],
            types:      vec![ qtype!(SOA) ],
            resolvers:  vec![ Resolver::Specified("1.1.1.1".into()) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn all_mixed_2() {
        let options = Options::getopts(&[ "CH", "SOA", "MX", "IN", "-q", "lookup.dog", "--class", "HS" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            classes:    vec![ QClass::HS, QClass::CH, QClass::IN ],
            types:      vec![ qtype!(SOA), qtype!(MX) ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn all_mixed_3() {
        let options = Options::getopts(&[ "lookup.dog", "--nameserver", "1.1.1.1", "--nameserver", "1.0.0.1" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("lookup.dog") ],
            resolvers:  vec![ Resolver::Specified("1.1.1.1".into()),
                              Resolver::Specified("1.0.0.1".into()), ],
            .. Inputs::fallbacks()
        });
    }

    #[test]
    fn explicit_numerics() {
        let options = Options::getopts(&[ "11", "--class", "22", "--type", "33" ]).unwrap();
        assert_eq!(options.requests.inputs, Inputs {
            domains:    vec![ String::from("11") ],
            classes:    vec![ QClass::Other(22) ],
            types:      vec![ 33 ],
            .. Inputs::fallbacks()
        });
    }

    // invalid options tests

    #[test]
    fn invalid_named_class() {
        assert_eq!(Options::getopts(&[ "lookup.dog", "--class", "tubes" ]),
                   OptionsResult::InvalidOptions(OptionsError::InvalidQueryClass("tubes".into())));
    }

    #[test]
    fn invalid_named_type() {
        assert_eq!(Options::getopts(&[ "lookup.dog", "--type", "tubes" ]),
                   OptionsResult::InvalidOptions(OptionsError::InvalidQueryType("tubes".into())));
    }

    #[test]
    fn invalid_capsword() {
        assert_eq!(Options::getopts(&[ "SMH", "lookup.dog" ]),
                   OptionsResult::InvalidOptions(OptionsError::InvalidQueryType("SMH".into())));
    }

    #[test]
    fn invalid_txid() {
        assert_eq!(Options::getopts(&[ "lookup.dog", "--txid=0x10000" ]),
                   OptionsResult::InvalidOptions(OptionsError::InvalidTxid("0x10000".into())));
    }

    #[test]
    fn opt() {
        assert_eq!(Options::getopts(&[ "OPT", "lookup.dog" ]),
                   OptionsResult::InvalidOptions(OptionsError::QueryTypeOPT));
    }

    // txid tests

    #[test]
    fn number_parsing() {
        assert_eq!(parse_dec_or_hex("1234"),    Some(1234));
        assert_eq!(parse_dec_or_hex("0x1234"),  Some(0x1234));
        assert_eq!(parse_dec_or_hex("0xABcd"),  Some(0xABcd));

        assert_eq!(parse_dec_or_hex("65536"),   None);
        assert_eq!(parse_dec_or_hex("0x65536"), None);

        assert_eq!(parse_dec_or_hex(""),        None);
        assert_eq!(parse_dec_or_hex("0x"),      None);
    }
}