use ref_cast::RefCast;
use serde::{Deserialize, Serialize};
use std::borrow::Cow;
use std::fmt::{Debug, Display};
use std::ops::{Deref, DerefMut};
use std::str::FromStr;
use thiserror::Error;
use url::Url;

#[derive(Error, Debug, Clone, PartialEq, Eq)]
pub enum DisplaySafeUrlError {
    /// Failed to parse a URL.
    #[error(transparent)]
    Url(#[from] url::ParseError),

    /// We parsed a URL, but couldn't disambiguate its authority
    /// component.
    #[error("ambiguous user/pass authority in URL (not percent-encoded?): {0}")]
    AmbiguousAuthority(String),
}

/// A [`Url`] wrapper that redacts credentials when displaying the URL.
///
/// `DisplaySafeUrl` wraps the standard [`url::Url`] type, providing functionality to mask
/// secrets by default when the URL is displayed or logged. This helps prevent accidental
/// exposure of sensitive information in logs and debug output.
///
/// # Examples
///
/// ```
/// use uv_redacted::DisplaySafeUrl;
/// use std::str::FromStr;
///
/// // Create a `DisplaySafeUrl` from a `&str`
/// let mut url = DisplaySafeUrl::parse("https://user:password@example.com").unwrap();
///
/// // Display will mask secrets
/// assert_eq!(url.to_string(), "https://user:****@example.com/");
///
/// // You can still access the username and password
/// assert_eq!(url.username(), "user");
/// assert_eq!(url.password(), Some("password"));
///
/// // And you can still update the username and password
/// let _ = url.set_username("new_user");
/// let _ = url.set_password(Some("new_password"));
/// assert_eq!(url.username(), "new_user");
/// assert_eq!(url.password(), Some("new_password"));
///
/// // It is also possible to remove the credentials entirely
/// url.remove_credentials();
/// assert_eq!(url.username(), "");
/// assert_eq!(url.password(), None);
/// ```
#[derive(Clone, Eq, PartialEq, PartialOrd, Ord, Hash, Serialize, Deserialize, RefCast)]
#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
#[cfg_attr(feature = "schemars", schemars(transparent))]
#[repr(transparent)]
pub struct DisplaySafeUrl(Url);

/// Check if a path or fragment contains a credential-like pattern (`:` followed by `@`).
///
/// This skips colons that are followed by `//`, as those indicate URL schemes (e.g., `https://`)
/// rather than credentials. This is important for handling nested URLs like proxy URLs:
/// `git+https://proxy.com/https://github.com/user/repo.git@branch`.
fn has_credential_like_pattern(s: &str) -> bool {
    let mut remaining = s;
    while let Some(colon_pos) = remaining.find(':') {
        let after_colon = &remaining[colon_pos + 1..];
        // If the colon is followed by "//", consider it a URL scheme.
        if after_colon.starts_with("//") {
            remaining = after_colon;
            continue;
        }
        // Check if there's an @ after this colon.
        if after_colon.contains('@') {
            return true;
        }
        remaining = after_colon;
    }
    false
}

impl DisplaySafeUrl {
    #[inline]
    pub fn parse(input: &str) -> Result<Self, DisplaySafeUrlError> {
        let url = Url::parse(input)?;

        Self::reject_ambiguous_credentials(input, &url)?;

        Ok(Self(url))
    }

    /// Reject some ambiguous cases, e.g., `https://user/name:password@domain/a/b/c`
    ///
    /// In this case the user *probably* meant to have a username of "user/name", but both RFC
    /// 3986 and WHATWG URL expect the userinfo (RFC 3986) or authority (WHATWG) to not contain a
    /// non-percent-encoded slash or other special character.
    ///
    /// This ends up being moderately annoying to detect, since the above gets parsed into a
    /// "valid" WHATWG URL where the host is `used` and the pathname is
    /// `/name:password@domain/a/b/c` rather than causing a parse error.
    ///
    /// To detect it, we use a heuristic: if the password component is missing but the path or
    /// fragment contain a `:` followed by a `@`, then we assume the URL is ambiguous.
    fn reject_ambiguous_credentials(input: &str, url: &Url) -> Result<(), DisplaySafeUrlError> {
        // `git://`, `http://`, and `https://` URLs may carry credentials, while `file://` URLs
        // on Windows may contain both sigils, but it's always safe, e.g.
        // `file://C:/Users/ferris/project@home/workspace`.
        if url.scheme() == "file" {
            return Ok(());
        }

        if url.password().is_some() {
            return Ok(());
        }

        // Check for the suspicious pattern.
        if !has_credential_like_pattern(url.path())
            && !url
                .fragment()
                .map(has_credential_like_pattern)
                .unwrap_or(false)
        {
            return Ok(());
        }

        // If the previous check passed, we should always expect to find these in the given URL.
        let (Some(col_pos), Some(at_pos)) = (input.find(':'), input.rfind('@')) else {
            if cfg!(debug_assertions) {
                unreachable!(
                    "`:` or `@` sign missing in URL that was confirmed to contain them: {input}"
                );
            }
            return Ok(());
        };

        // Our ambiguous URL probably has credentials in it, so we don't want to blast it out in
        // the error message. We somewhat aggressively replace everything between the scheme's
        // ':' and the lastmost `@` with `***`.
        let redacted_path = format!("{}***{}", &input[0..=col_pos], &input[at_pos..]);
        Err(DisplaySafeUrlError::AmbiguousAuthority(redacted_path))
    }

    /// Create a new [`DisplaySafeUrl`] from a [`Url`].
    ///
    /// Unlike [`Self::parse`], this doesn't perform any ambiguity checks.
    /// That means that it's primarily useful for contexts where a human can't easily accidentally
    /// introduce an ambiguous URL, such as URLs being read from a request.
    pub fn from_url(url: Url) -> Self {
        Self(url)
    }

    /// Cast a `&Url` to a `&DisplaySafeUrl` using ref-cast.
    #[inline]
    pub fn ref_cast(url: &Url) -> &Self {
        RefCast::ref_cast(url)
    }

    /// Parse a string as an URL, with this URL as the base URL.
    #[inline]
    pub fn join(&self, input: &str) -> Result<Self, DisplaySafeUrlError> {
        Ok(Self(self.0.join(input)?))
    }

    /// Serialize with Serde using the internal representation of the `Url` struct.
    #[inline]
    pub fn serialize_internal<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        self.0.serialize_internal(serializer)
    }

    /// Serialize with Serde using the internal representation of the `Url` struct.
    #[inline]
    pub fn deserialize_internal<'de, D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        Ok(Self(Url::deserialize_internal(deserializer)?))
    }

    #[allow(clippy::result_unit_err)]
    pub fn from_file_path<P: AsRef<std::path::Path>>(path: P) -> Result<Self, ()> {
        Ok(Self(Url::from_file_path(path)?))
    }

    /// Remove the credentials from a URL, allowing the generic `git` username (without a password)
    /// in SSH URLs, as in, `ssh://git@github.com/...`.
    #[inline]
    pub fn remove_credentials(&mut self) {
        // For URLs that use the `git` convention (i.e., `ssh://git@github.com/...`), avoid dropping the
        // username.
        if is_ssh_git_username(&self.0) {
            return;
        }
        let _ = self.0.set_username("");
        let _ = self.0.set_password(None);
    }

    /// Returns the URL with any credentials removed.
    pub fn without_credentials(&self) -> Cow<'_, Url> {
        if self.0.password().is_none() && self.0.username() == "" {
            return Cow::Borrowed(&self.0);
        }

        // For URLs that use the `git` convention (i.e., `ssh://git@github.com/...`), avoid dropping the
        // username.
        if is_ssh_git_username(&self.0) {
            return Cow::Borrowed(&self.0);
        }

        let mut url = self.0.clone();
        let _ = url.set_username("");
        let _ = url.set_password(None);
        Cow::Owned(url)
    }

    /// Returns [`Display`] implementation that doesn't mask credentials.
    #[inline]
    pub fn displayable_with_credentials(&self) -> impl Display {
        &self.0
    }
}

impl Deref for DisplaySafeUrl {
    type Target = Url;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for DisplaySafeUrl {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl Display for DisplaySafeUrl {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        display_with_redacted_credentials(&self.0, f)
    }
}

impl Debug for DisplaySafeUrl {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let url = &self.0;
        // For URLs that use the `git` convention (i.e., `ssh://git@github.com/...`), avoid masking the
        // username.
        let (username, password) = if is_ssh_git_username(url) {
            (url.username(), None)
        } else if url.username() != "" && url.password().is_some() {
            (url.username(), Some("****"))
        } else if url.username() != "" {
            ("****", None)
        } else if url.password().is_some() {
            ("", Some("****"))
        } else {
            ("", None)
        };

        f.debug_struct("DisplaySafeUrl")
            .field("scheme", &url.scheme())
            .field("cannot_be_a_base", &url.cannot_be_a_base())
            .field("username", &username)
            .field("password", &password)
            .field("host", &url.host())
            .field("port", &url.port())
            .field("path", &url.path())
            .field("query", &url.query())
            .field("fragment", &url.fragment())
            .finish()
    }
}

impl From<DisplaySafeUrl> for Url {
    fn from(url: DisplaySafeUrl) -> Self {
        url.0
    }
}

impl From<Url> for DisplaySafeUrl {
    fn from(url: Url) -> Self {
        Self(url)
    }
}

impl FromStr for DisplaySafeUrl {
    type Err = DisplaySafeUrlError;

    fn from_str(input: &str) -> Result<Self, Self::Err> {
        Self::parse(input)
    }
}

fn is_ssh_git_username(url: &Url) -> bool {
    matches!(url.scheme(), "ssh" | "git+ssh" | "git+https")
        && url.username() == "git"
        && url.password().is_none()
}

fn display_with_redacted_credentials(
    url: &Url,
    f: &mut std::fmt::Formatter<'_>,
) -> std::fmt::Result {
    if url.password().is_none() && url.username() == "" {
        return write!(f, "{url}");
    }

    // For URLs that use the `git` convention (i.e., `ssh://git@github.com/...`), avoid dropping the
    // username.
    if is_ssh_git_username(url) {
        return write!(f, "{url}");
    }

    write!(f, "{}://", url.scheme())?;

    if url.username() != "" && url.password().is_some() {
        write!(f, "{}", url.username())?;
        write!(f, ":****@")?;
    } else if url.username() != "" {
        write!(f, "****@")?;
    } else if url.password().is_some() {
        write!(f, ":****@")?;
    }

    write!(f, "{}", url.host_str().unwrap_or(""))?;

    if let Some(port) = url.port() {
        write!(f, ":{port}")?;
    }

    write!(f, "{}", url.path())?;
    if let Some(query) = url.query() {
        write!(f, "?{query}")?;
    }
    if let Some(fragment) = url.fragment() {
        write!(f, "#{fragment}")?;
    }

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn from_url_no_credentials() {
        let url_str = "https://pypi-proxy.fly.dev/basic-auth/simple";
        let log_safe_url =
            DisplaySafeUrl::parse("https://pypi-proxy.fly.dev/basic-auth/simple").unwrap();
        assert_eq!(log_safe_url.username(), "");
        assert!(log_safe_url.password().is_none());
        assert_eq!(log_safe_url.to_string(), url_str);
    }

    #[test]
    fn from_url_username_and_password() {
        let log_safe_url =
            DisplaySafeUrl::parse("https://user:pass@pypi-proxy.fly.dev/basic-auth/simple")
                .unwrap();
        assert_eq!(log_safe_url.username(), "user");
        assert!(log_safe_url.password().is_some_and(|p| p == "pass"));
        assert_eq!(
            log_safe_url.to_string(),
            "https://user:****@pypi-proxy.fly.dev/basic-auth/simple"
        );
    }

    #[test]
    fn from_url_just_password() {
        let log_safe_url =
            DisplaySafeUrl::parse("https://:pass@pypi-proxy.fly.dev/basic-auth/simple").unwrap();
        assert_eq!(log_safe_url.username(), "");
        assert!(log_safe_url.password().is_some_and(|p| p == "pass"));
        assert_eq!(
            log_safe_url.to_string(),
            "https://:****@pypi-proxy.fly.dev/basic-auth/simple"
        );
    }

    #[test]
    fn from_url_just_username() {
        let log_safe_url =
            DisplaySafeUrl::parse("https://user@pypi-proxy.fly.dev/basic-auth/simple").unwrap();
        assert_eq!(log_safe_url.username(), "user");
        assert!(log_safe_url.password().is_none());
        assert_eq!(
            log_safe_url.to_string(),
            "https://****@pypi-proxy.fly.dev/basic-auth/simple"
        );
    }

    #[test]
    fn from_url_git_username() {
        let ssh_str = "ssh://git@github.com/org/repo";
        let ssh_url = DisplaySafeUrl::parse(ssh_str).unwrap();
        assert_eq!(ssh_url.username(), "git");
        assert!(ssh_url.password().is_none());
        assert_eq!(ssh_url.to_string(), ssh_str);
        // Test again for the `git+ssh` scheme
        let git_ssh_str = "git+ssh://git@github.com/org/repo";
        let git_ssh_url = DisplaySafeUrl::parse(git_ssh_str).unwrap();
        assert_eq!(git_ssh_url.username(), "git");
        assert!(git_ssh_url.password().is_none());
        assert_eq!(git_ssh_url.to_string(), git_ssh_str);
    }

    #[test]
    fn parse_url_string() {
        let url_str = "https://user:pass@pypi-proxy.fly.dev/basic-auth/simple";
        let log_safe_url = DisplaySafeUrl::parse(url_str).unwrap();
        assert_eq!(log_safe_url.username(), "user");
        assert!(log_safe_url.password().is_some_and(|p| p == "pass"));
        assert_eq!(
            log_safe_url.to_string(),
            "https://user:****@pypi-proxy.fly.dev/basic-auth/simple"
        );
    }

    #[test]
    fn remove_credentials() {
        let url_str = "https://user:pass@pypi-proxy.fly.dev/basic-auth/simple";
        let mut log_safe_url = DisplaySafeUrl::parse(url_str).unwrap();
        log_safe_url.remove_credentials();
        assert_eq!(log_safe_url.username(), "");
        assert!(log_safe_url.password().is_none());
        assert_eq!(
            log_safe_url.to_string(),
            "https://pypi-proxy.fly.dev/basic-auth/simple"
        );
    }

    #[test]
    fn preserve_ssh_git_username_on_remove_credentials() {
        let ssh_str = "ssh://git@pypi-proxy.fly.dev/basic-auth/simple";
        let mut ssh_url = DisplaySafeUrl::parse(ssh_str).unwrap();
        ssh_url.remove_credentials();
        assert_eq!(ssh_url.username(), "git");
        assert!(ssh_url.password().is_none());
        assert_eq!(ssh_url.to_string(), ssh_str);
        // Test again for `git+ssh` scheme
        let git_ssh_str = "git+ssh://git@pypi-proxy.fly.dev/basic-auth/simple";
        let mut git_shh_url = DisplaySafeUrl::parse(git_ssh_str).unwrap();
        git_shh_url.remove_credentials();
        assert_eq!(git_shh_url.username(), "git");
        assert!(git_shh_url.password().is_none());
        assert_eq!(git_shh_url.to_string(), git_ssh_str);
    }

    #[test]
    fn displayable_with_credentials() {
        let url_str = "https://user:pass@pypi-proxy.fly.dev/basic-auth/simple";
        let log_safe_url = DisplaySafeUrl::parse(url_str).unwrap();
        assert_eq!(
            log_safe_url.displayable_with_credentials().to_string(),
            url_str
        );
    }

    #[test]
    fn url_join() {
        let url_str = "https://token@example.com/abc/";
        let log_safe_url = DisplaySafeUrl::parse(url_str).unwrap();
        let foo_url = log_safe_url.join("foo").unwrap();
        assert_eq!(foo_url.to_string(), "https://****@example.com/abc/foo");
    }

    #[test]
    fn log_safe_url_ref() {
        let url_str = "https://user:pass@pypi-proxy.fly.dev/basic-auth/simple";
        let url = DisplaySafeUrl::parse(url_str).unwrap();
        let log_safe_url = DisplaySafeUrl::ref_cast(&url);
        assert_eq!(log_safe_url.username(), "user");
        assert!(log_safe_url.password().is_some_and(|p| p == "pass"));
        assert_eq!(
            log_safe_url.to_string(),
            "https://user:****@pypi-proxy.fly.dev/basic-auth/simple"
        );
    }

    #[test]
    fn parse_url_ambiguous() {
        for url in &[
            "https://user/name:password@domain/a/b/c",
            "https://user\\name:password@domain/a/b/c",
            "https://user#name:password@domain/a/b/c",
            "https://user.com/name:password@domain/a/b/c",
        ] {
            let err = DisplaySafeUrl::parse(url).unwrap_err();
            match err {
                DisplaySafeUrlError::AmbiguousAuthority(redacted) => {
                    assert!(redacted.starts_with("https:***@domain/a/b/c"));
                }
                DisplaySafeUrlError::Url(_) => panic!("expected AmbiguousAuthority error"),
            }
        }
    }

    #[test]
    fn parse_url_not_ambiguous() {
        for url in &[
            // https://github.com/astral-sh/uv/issues/16756
            "file:///C:/jenkins/ython_Environment_Manager_PR-251@2/venv%201/workspace",
            // https://github.com/astral-sh/uv/issues/17214
            // Git proxy URLs with nested schemes should not trigger the ambiguity check
            "git+https://githubproxy.cc/https://github.com/user/repo.git@branch",
            "git+https://proxy.example.com/https://github.com/org/project@v1.0.0",
            "git+https://proxy.example.com/https://github.com/org/project@refs/heads/main",
        ] {
            DisplaySafeUrl::parse(url).unwrap();
        }
    }

    #[test]
    fn credential_like_pattern() {
        assert!(!has_credential_like_pattern(
            "/https://github.com/user/repo.git@branch"
        ));
        assert!(!has_credential_like_pattern("/http://example.com/path@ref"));

        assert!(has_credential_like_pattern("/name:password@domain/a/b/c"));
        assert!(has_credential_like_pattern(":password@domain"));
    }
}
