use std::{
    borrow::Cow,
    cmp, fmt,
    fmt::Write,
    str::FromStr,
    time::{SystemTime, UNIX_EPOCH},
};

use argon2::{password_hash, Argon2, PasswordHasher, PasswordVerifier};
use cmp::Ordering;
use rand::{prelude::*, rngs::OsRng};
use ring::digest;
use ruma::{
    api::client::error::ErrorKind, canonical_json::try_from_json_map,
    CanonicalJsonError, CanonicalJsonObject, MxcUri, MxcUriError, OwnedMxcUri,
};

use crate::{Error, Result};

pub(crate) mod error;
pub(crate) mod on_demand_hashmap;
pub(crate) mod proxy_protocol;
pub(crate) mod room_version;

// Hopefully we have a better chat protocol in 530 years
#[allow(clippy::as_conversions, clippy::cast_possible_truncation)]
pub(crate) fn millis_since_unix_epoch() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .expect("time is valid")
        .as_millis() as u64
}

#[cfg(any(feature = "rocksdb", feature = "sqlite"))]
pub(crate) fn increment(old: Option<&[u8]>) -> Vec<u8> {
    let number = match old.map(TryInto::try_into) {
        Some(Ok(bytes)) => {
            let number = u64::from_be_bytes(bytes);
            number + 1
        }
        // Start at one. since 0 should return the first event in the db
        _ => 1,
    };

    number.to_be_bytes().to_vec()
}

pub(crate) fn generate_keypair() -> Vec<u8> {
    let mut value = random_string(8).as_bytes().to_vec();
    value.push(0xFF);
    value.extend_from_slice(
        &ruma::signatures::Ed25519KeyPair::generate()
            .expect("Ed25519KeyPair generation always works (?)"),
    );
    value
}

/// Parses the bytes into an u64.
pub(crate) fn u64_from_bytes(
    bytes: &[u8],
) -> Result<u64, std::array::TryFromSliceError> {
    let array: [u8; 8] = bytes.try_into()?;
    Ok(u64::from_be_bytes(array))
}

/// Parses the bytes into a string.
pub(crate) fn string_from_bytes(
    bytes: &[u8],
) -> Result<String, std::string::FromUtf8Error> {
    String::from_utf8(bytes.to_vec())
}

pub(crate) fn random_string(length: usize) -> String {
    thread_rng()
        .sample_iter(&rand::distributions::Alphanumeric)
        .take(length)
        .map(char::from)
        .collect()
}

/// Hash the given password
pub(crate) fn hash_password<B>(
    password: B,
) -> Result<password_hash::PasswordHashString, password_hash::Error>
where
    B: AsRef<[u8]>,
{
    Argon2::default()
        .hash_password(
            password.as_ref(),
            &password_hash::SaltString::generate(&mut OsRng),
        )
        .map(|x| x.serialize())
}

/// Compare a password to a hash
///
/// Returns `true` if the password matches the hash, `false` otherwise.
pub(crate) fn verify_password<S, B>(hash: S, password: B) -> bool
where
    S: AsRef<str>,
    B: AsRef<[u8]>,
{
    let Ok(hash) = password_hash::PasswordHash::new(hash.as_ref()) else {
        return false;
    };

    Argon2::default().verify_password(password.as_ref(), &hash).is_ok()
}

#[tracing::instrument(skip(keys))]
pub(crate) fn calculate_hash<'a, I, T>(keys: I) -> Vec<u8>
where
    I: IntoIterator<Item = T>,
    T: AsRef<[u8]>,
{
    let mut bytes = Vec::new();
    for (i, key) in keys.into_iter().enumerate() {
        if i != 0 {
            bytes.push(0xFF);
        }
        bytes.extend_from_slice(key.as_ref());
    }
    let hash = digest::digest(&digest::SHA256, &bytes);
    hash.as_ref().to_owned()
}

pub(crate) fn common_elements<I, T, F>(
    mut iterators: I,
    check_order: F,
) -> Option<impl Iterator<Item = T>>
where
    I: Iterator,
    I::Item: Iterator<Item = T>,
    F: Fn(&T, &T) -> Ordering,
{
    let first_iterator = iterators.next()?;
    let mut other_iterators =
        iterators.map(Iterator::peekable).collect::<Vec<_>>();

    Some(first_iterator.filter(move |target| {
        other_iterators.iter_mut().all(|it| {
            while let Some(element) = it.peek() {
                match check_order(element, target) {
                    // We went too far
                    Ordering::Greater => return false,
                    // Element is in both iters
                    Ordering::Equal => return true,
                    // Keep searching
                    Ordering::Less => {
                        it.next();
                    }
                }
            }
            false
        })
    }))
}

/// Fallible conversion from any value that implements `Serialize` to a
/// `CanonicalJsonObject`.
///
/// `value` must serialize to an `serde_json::Value::Object`.
pub(crate) fn to_canonical_object<T: serde::Serialize>(
    value: T,
) -> Result<CanonicalJsonObject, CanonicalJsonError> {
    use serde::ser::Error;

    match serde_json::to_value(value).map_err(CanonicalJsonError::SerDe)? {
        serde_json::Value::Object(map) => try_from_json_map(map),
        _ => Err(CanonicalJsonError::SerDe(serde_json::Error::custom(
            "Value must be an object",
        ))),
    }
}

pub(crate) fn deserialize_from_str<
    'de,
    D: serde::de::Deserializer<'de>,
    T: FromStr<Err = E>,
    E: fmt::Display,
>(
    deserializer: D,
) -> Result<T, D::Error> {
    struct Visitor<T: FromStr<Err = E>, E>(std::marker::PhantomData<T>);
    impl<T: FromStr<Err = Err>, Err: fmt::Display> serde::de::Visitor<'_>
        for Visitor<T, Err>
    {
        type Value = T;

        fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
            write!(formatter, "a parsable string")
        }

        fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
        where
            E: serde::de::Error,
        {
            v.parse().map_err(serde::de::Error::custom)
        }
    }
    deserializer.deserialize_str(Visitor(std::marker::PhantomData))
}

/// Debug-formats the given slice, but only up to the first `max_len` elements.
/// Any further elements are replaced by an ellipsis.
///
/// See also [`debug_slice_truncated()`],
pub(crate) struct TruncatedDebugSlice<'a, T> {
    inner: &'a [T],
    max_len: usize,
}

impl<T: fmt::Debug> fmt::Debug for TruncatedDebugSlice<'_, T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.inner.len() <= self.max_len {
            write!(f, "{:?}", self.inner)
        } else {
            f.debug_list()
                .entries(&self.inner[..self.max_len])
                .entry(&"...")
                .finish()
        }
    }
}

/// See [`TruncatedDebugSlice`]. Useful for `#[instrument]`:
///
/// ```ignore
/// #[tracing::instrument(fields(
///     foos = debug_slice_truncated(foos, N)
/// ))]
/// ```
pub(crate) fn debug_slice_truncated<T: fmt::Debug>(
    slice: &[T],
    max_len: usize,
) -> tracing::field::DebugValue<TruncatedDebugSlice<'_, T>> {
    tracing::field::debug(TruncatedDebugSlice {
        inner: slice,
        max_len,
    })
}

/// Truncates a string to an approximate maximum length, replacing any extra
/// text with an ellipsis.
///
/// Only to be used for informational purposes, exact semantics are unspecified.
pub(crate) fn dbg_truncate_str(s: &str, mut max_len: usize) -> Cow<'_, str> {
    while max_len < s.len() && !s.is_char_boundary(max_len) {
        max_len += 1;
    }

    if s.len() <= max_len {
        s.into()
    } else {
        #[allow(clippy::string_slice)] // we checked it's at a char boundary
        format!("{}...", &s[..max_len]).into()
    }
}

/// Data that makes up an `mxc://` URL.
#[derive(Debug, Clone)]
pub(crate) struct MxcData<'a> {
    pub(crate) server_name: &'a ruma::ServerName,
    pub(crate) media_id: &'a str,
}

impl<'a> MxcData<'a> {
    pub(crate) fn new(
        server_name: &'a ruma::ServerName,
        media_id: &'a str,
    ) -> Result<Self> {
        if !media_id.bytes().all(|b| {
            matches!(b,
                b'0'..=b'9' | b'a'..=b'z' | b'A'..=b'Z' | b'-' | b'_'
            )
        }) {
            return Err(Error::BadRequest(
                ErrorKind::InvalidParam,
                "Invalid MXC media id",
            ));
        }

        Ok(Self {
            server_name,
            media_id,
        })
    }
}

impl fmt::Display for MxcData<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "mxc://{}/{}", self.server_name, self.media_id)
    }
}

impl From<MxcData<'_>> for OwnedMxcUri {
    fn from(value: MxcData<'_>) -> Self {
        value.to_string().into()
    }
}

impl<'a> TryFrom<&'a MxcUri> for MxcData<'a> {
    type Error = MxcUriError;

    fn try_from(value: &'a MxcUri) -> Result<Self, Self::Error> {
        Ok(Self::new(value.server_name()?, value.media_id()?)
            .expect("validated MxcUri should always be valid MxcData"))
    }
}

fn curlify_args<T>(req: &http::Request<T>) -> Option<Vec<String>> {
    let mut args =
        vec!["curl".to_owned(), "-X".to_owned(), req.method().to_string()];

    for (name, val) in req.headers() {
        args.extend([
            "-H".to_owned(),
            format!("{name}: {}", val.to_str().ok()?),
        ]);
    }

    let fix_uri = || {
        if req.uri().scheme().is_some() {
            return None;
        }
        if req.uri().authority().is_some() {
            return None;
        }
        let mut parts = req.uri().clone().into_parts();

        parts.scheme = Some(http::uri::Scheme::HTTPS);

        let host =
            req.headers().get(http::header::HOST)?.to_str().ok()?.to_owned();
        parts.authority =
            Some(http::uri::Authority::from_maybe_shared(host).ok()?);

        http::uri::Uri::from_parts(parts).ok()
    };

    let uri = if let Some(new_uri) = fix_uri() {
        Cow::Owned(new_uri)
    } else {
        Cow::Borrowed(req.uri())
    };

    args.push(uri.to_string());

    Some(args)
}

pub(crate) fn curlify<T>(req: &http::Request<T>) -> Option<String> {
    let args = curlify_args(req)?;

    Some(
        args.into_iter()
            .map(|arg| {
                if arg.chars().all(|c| {
                    c.is_alphanumeric() || ['-', '_', ':', '/'].contains(&c)
                }) {
                    arg
                } else {
                    format!("'{}'", arg.replace('\'', "\\'"))
                }
            })
            .collect::<Vec<_>>()
            .join(" "),
    )
}

/// Format a u8 slice as an uppercase hex string
///
/// The output does not contain a leading `0x` nor any non-hex characters (e.g.
/// whitespace or commas do not appear in the output).
pub(crate) fn u8_slice_to_hex(slice: &[u8]) -> String {
    slice.iter().fold(String::new(), |mut acc, x| {
        write!(acc, "{x:02X}").expect("in-memory write should succeed");
        acc
    })
}

#[cfg(test)]
mod tests {
    use crate::utils::{dbg_truncate_str, u8_slice_to_hex};

    #[test]
    fn test_truncate_str() {
        assert_eq!(dbg_truncate_str("short", 10), "short");
        assert_eq!(dbg_truncate_str("very long string", 10), "very long ...");
        assert_eq!(dbg_truncate_str("no info, only dots", 0), "...");
        assert_eq!(dbg_truncate_str("", 0), "");
        assert_eq!(dbg_truncate_str("unicöde", 5), "unicö...");
        let ok_hand = "👌🏽";
        assert_eq!(dbg_truncate_str(ok_hand, 1), "👌...");
        assert_eq!(dbg_truncate_str(ok_hand, ok_hand.len() - 1), "👌🏽");
        assert_eq!(dbg_truncate_str(ok_hand, ok_hand.len()), "👌🏽");
    }

    #[test]
    fn test_slice_to_hex() {
        assert_eq!(u8_slice_to_hex(&[]), "");
        assert_eq!(u8_slice_to_hex(&[0]), "00");
        assert_eq!(u8_slice_to_hex(&[0xFF]), "FF");
        assert_eq!(u8_slice_to_hex(&[1, 2, 3, 4]), "01020304");
        assert_eq!(
            u8_slice_to_hex(&[0x42; 100]),
            "4242424242424242424242424242424242424242\
             4242424242424242424242424242424242424242\
             4242424242424242424242424242424242424242\
             4242424242424242424242424242424242424242\
             4242424242424242424242424242424242424242"
        );
    }
}