use alloc::borrow::{Cow, ToOwned};
use alloc::string::String;

#[cfg(feature = "regex")]
use regex::Regex;
use serde::{
    de::{Error as SerdeError, Unexpected},
    Deserialize, Deserializer, Serialize,
};
use url::Url;

use core::cmp::Ordering;

#[cfg(feature = "std")]
use crate::{Error, Result};

/// Alias for an owned [`Id`].
pub type IdBuf = Id<'static>;

// todo: check patterns with regex debugger
/// A list of possible YouTube video identifier patterns.
///
/// ## Guarantees:
/// - each pattern contains an `id` group that will always capture when the pattern matches
/// - The captured id will always match following regex (defined in [ID_PATTERN]): `^[a-zA-Z0-9_-]{11}$`
#[cfg(feature = "regex")]
pub static ID_PATTERNS: [&once_cell::sync::Lazy<Regex>; 5] = [
    &WATCH_URL_PATTERN,
    &SHORTS_URL_PATTERN,
    &EMBED_URL_PATTERN,
    &SHARE_URL_PATTERN,
    &ID_PATTERN
];
/// A pattern matching the watch url of a video (i.e. `youtube.com/watch?v=<ID>`).
#[cfg(feature = "regex")]
pub static WATCH_URL_PATTERN: once_cell::sync::Lazy<Regex> = once_cell::sync::Lazy::new(||
    // watch url    (i.e. https://youtube.com/watch?v=video_id)
    Regex::new(r"^(https?://)?(www\.)?youtube.\w\w\w?/watch\?v=(?P<id>[a-zA-Z0-9_-]{11})(&.*)?$").unwrap()
);
/// A pattern matching the shorts url of a video (i.e. `https://youtube.com/shorts/<ID>`).
#[cfg(feature = "regex")]
pub static SHORTS_URL_PATTERN: once_cell::sync::Lazy<Regex> = once_cell::sync::Lazy::new(||
    Regex::new(r"^(https?://)?(www\.)?youtube.\w\w\w?/shorts/(?P<id>[a-zA-Z0-9_-]{11})(\?.*)?$").unwrap()
);
/// A pattern matching the embedded url of a video (i.e. `youtube.com/embed/<ID>`).
#[cfg(feature = "regex")]
pub static EMBED_URL_PATTERN: once_cell::sync::Lazy<Regex> = once_cell::sync::Lazy::new(||
    // embed url    (i.e. https://youtube.com/embed/video_id)
    Regex::new(r"^(https?://)?(www\.)?youtube.\w\w\w?/embed/(?P<id>[a-zA-Z0-9_-]{11})\\?(\?.*)?$").unwrap()
);
/// A pattern matching the embedded url of a video (i.e. `youtu.be/<ID>`).
#[cfg(feature = "regex")]
pub static SHARE_URL_PATTERN: once_cell::sync::Lazy<Regex> = once_cell::sync::Lazy::new(||
    // share url    (i.e. https://youtu.be/video_id)
    Regex::new(r"^(https?://)?youtu\.be/(?P<id>[a-zA-Z0-9_-]{11})$").unwrap()
);
/// A pattern matching the id of a video (`^[a-zA-Z0-9_-]{11}$`).
#[cfg(feature = "regex")]
pub static ID_PATTERN: once_cell::sync::Lazy<Regex> = once_cell::sync::Lazy::new(||
    // id          (i.e. video_id)
    Regex::new("^(?P<id>[a-zA-Z0-9_-]{11})$").unwrap()
);

/// A wrapper around a Cow<'a, str> that makes sure the video id, which is contained, always
/// has the correct format.
///
///
/// ## Guaranties:
/// Since YouTube does not guarantee a consistent video-id format, these guarantees can change in
/// major version updates. If your application depends on them, make sure to check this section on
/// regular bases!
///
/// - The id will always match following regex (defined in [ID_PATTERN]): `^[a-zA-Z0-9_-]{11}$`
/// - The id can always be used as a valid url segment
/// - The id can always be used as a valid url parameter
///
/// ## Ownership
/// All available constructors except for [`Id::deserialize`] and [`Id::from_string`] will
/// create the borrowed version with the lifetime of the input. Therefore no allocation is required.
///
/// If you don't need 'static deserialization, you can use [`Id::deserialize_borrowed`], which will
/// create an `Id<'de>`.
///
/// If you require [`Id`] to be owned (`Id<'static`>), you can use [`Id::as_owned`] or
/// [`Id::into_owned`], which both can easily be chained. You can also use [`IdBuf`], which is
/// an alias for `Id<'static>`, to make functions and types less verbose.
#[derive(Clone, Debug, Serialize, Hash)]
pub struct Id<'a>(Cow<'a, str>);

#[allow(clippy::should_implement_trait)]
impl<'a> Id<'a> {
    cfg_if::cfg_if! {
        if #[cfg(feature = "regex")] {
            pub fn from_raw(raw: &'a str) -> Result<Self> {
                ID_PATTERNS
                    .iter()
                    .find_map(|pattern|
                        pattern
                            .captures(raw)
                            .map(|c| {
                                // will never panic due to guarantees by [`ID_PATTERNS`]
                                let id = c.name("id").unwrap().as_str();
                                Self(Cow::Borrowed(id))
                            })
                    )
                    .ok_or(Error::BadIdFormat)
            }

            #[inline]
            pub fn from_str(id: &'a str) -> Result<Self> {
                match ID_PATTERN.is_match(id) {
                    true => Ok(Self(Cow::Borrowed(id))),
                    false => Err(Error::BadIdFormat)
                }
            }
        } else {
            #[inline]
            pub fn from_str(id: &'a str) -> Option<Self> {
                match Self::check_str(id) {
                    Ok(_) => Some(Self(Cow::Borrowed(id))),
                    Err(_) => None
                }
            }

            #[inline]
            fn check_str(id: &'_ str) -> Result<(), ()> {
                if id.len() != 11 {
                    return Err(());
                }

                let only_allowed_chars = id
                    .chars()
                    .all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_');

                if only_allowed_chars {
                    Ok(())
                } else {
                    Err(())
                }
            }
        }
    }
}

impl<'a> Id<'a> {
    #[inline]
    pub fn is_borrowed(&self) -> bool {
        matches!(self.0, Cow::Borrowed(_))
    }

    #[inline]
    pub fn is_owned(&self) -> bool {
        matches!(self.0, Cow::Owned(_))
    }

    #[inline]
    pub fn make_owned(&mut self) -> &mut Self {
        if let Cow::Borrowed(id) = self.0 {
            self.0 = Cow::Owned(id.to_owned());
        }
        self
    }

    #[inline]
    #[must_use]
    pub fn into_owned(self) -> IdBuf {
        match self.0 {
            Cow::Owned(id) => Id(Cow::Owned(id)),
            Cow::Borrowed(id) => Id(Cow::Owned(id.to_owned()))
        }
    }

    #[inline]
    #[must_use]
    pub fn as_owned(&self) -> IdBuf {
        self
            .clone()
            .into_owned()
    }

    #[inline]
    #[must_use]
    pub fn as_borrowed(&'a self) -> Self {
        Self(Cow::Borrowed(&self.0))
    }

    #[inline]
    #[must_use]
    pub fn as_str(&self) -> &str {
        self.0.as_ref()
    }

    #[inline]
    #[must_use]
    pub fn watch_url(&self) -> Url {
        Url::parse_with_params(
            "https://www.youtube.com/watch?",
            &[("v", self.as_str())],
        ).unwrap()
    }

    #[inline]
    #[must_use]
    pub fn shorts_url(&self) -> Url {
        let mut url = Url::parse("https://www.youtube.com/shorts")
            .unwrap();
        url
            .path_segments_mut()
            .unwrap()
            .push(self.as_str());
        url
    }

    #[inline]
    #[must_use]
    pub fn embed_url(&self) -> Url {
        let mut url = Url::parse("https://www.youtube.com/embed")
            .unwrap();
        url
            .path_segments_mut()
            .unwrap()
            .push(self.as_str());
        url
    }

    #[inline]
    #[must_use]
    pub fn share_url(&self) -> Url {
        let mut url = Url::parse("https://youtu.be")
            .unwrap();
        url
            .path_segments_mut()
            .unwrap()
            .push(self.as_str());
        url
    }
}

impl IdBuf {
    cfg_if::cfg_if! {
        if #[cfg(feature = "regex")] {
            #[inline]
            pub fn from_string(id: String) -> Result<Self, String> {
                match ID_PATTERN.is_match(id.as_str()) {
                    true => Ok(Self(Cow::Owned(id))),
                    false => Err(id)
                }
            }
        } else {
            #[inline]
            pub fn from_string(id: String) -> Result<Self, String> {
                match Self::check_str(&id) {
                    Ok(_) => Ok(Self(Cow::Owned(id))),
                    Err(_) => Err(id)
                }
            }
        }
    }
}

impl<'de> Id<'de> {
    #[inline]
    pub fn deserialize_borrowed<D>(deserializer: D) -> Result<Self, <D as Deserializer<'de>>::Error>
        where
            D: Deserializer<'de> {
        let raw = <&'de str>::deserialize(deserializer)?;
        #[cfg(not(all(feature = "regex", feature = "std")))]
            let res = Self::from_str(raw).ok_or(());
        #[cfg(all(feature = "regex", feature = "std"))]
            let res = Self::from_raw(raw);

        res
            .map_err(|_| D::Error::invalid_value(
                Unexpected::Str(raw),
                &"expected a valid youtube video identifier",
            ))
    }
}

impl<'de> Deserialize<'de> for Id<'static> {
    #[inline]
    fn deserialize<D>(deserializer: D) -> Result<Self, <D as Deserializer<'de>>::Error>
        where
            D: Deserializer<'de> {
        let raw = String::deserialize(deserializer)?;
        Self::from_string(raw)
            .map_err(|s| D::Error::invalid_value(
                Unexpected::Str(&s),
                &"expected a valid youtube video identifier",
            ))
    }
}


impl core::fmt::Display for Id<'_> {
    #[inline]
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl core::ops::Deref for Id<'_> {
    type Target = str;

    #[inline]
    fn deref(&self) -> &Self::Target {
        self.as_str()
    }
}

impl core::convert::AsRef<str> for Id<'_> {
    #[inline]
    fn as_ref(&self) -> &str {
        self.as_str()
    }
}

impl<T> core::cmp::PartialEq<T> for Id<'_>
    where
        T: core::convert::AsRef<str> {
    #[inline]
    fn eq(&self, other: &T) -> bool {
        core::cmp::PartialEq::eq(
            self.as_str(),
            other.as_ref(),
        )
    }
}

impl core::cmp::Eq for Id<'_> {}

impl core::cmp::Ord for Id<'_> {
    #[inline]
    fn cmp(&self, other: &Self) -> Ordering {
        self.as_str().cmp(other.as_str())
    }
}

impl<T> core::cmp::PartialOrd<T> for Id<'_>
    where
        T: AsRef<str> {
    #[inline]
    fn partial_cmp(&self, other: &T) -> Option<Ordering> {
        core::cmp::PartialOrd::partial_cmp(
            self.as_str(),
            other.as_ref(),
        )
    }
}