use crate::twitch::Capability;
use std::collections::BTreeSet;

/**
User configuration for 'registering' with Twitch

This is used to *register* the connection with the server

It contains your user name, your OAuth token and the capabilities you want to request.

# example using a builder
```
# use twitchchat::twitch::{Capability, UserConfig};
# std::env::set_var("TWITCH_NAME", "foo");
# std::env::set_var("TWITCH_TOKEN", format!("oauth:{}", "a".repeat(30)));
// as anonymous
let config = UserConfig::builder().anonymous().build().unwrap();
// or with a name/token
let name = std::env::var("TWITCH_NAME").unwrap();
let token = std::env::var("TWITCH_TOKEN").unwrap();
let config = UserConfig::builder()
    .name(name)
    .token(token)
    .capabilities(&[Capability::Tags])
    .build()
    .unwrap();
```
*/
#[derive(Debug, Clone, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct UserConfig {
    /// Requested name of your user

    pub name: String,
    /// OAuth token of the user

    pub token: String,
    /// Capabilities to be requested from the server

    pub capabilities: Vec<Capability>,
}

impl UserConfig {
    /// Create a builder to make a [UserConfig]

    pub fn builder() -> UserConfigBuilder {
        UserConfigBuilder::default()
    }

    /// Determines whether this config was requested as anonymous

    pub fn is_anonymous(&self) -> bool {
        self.name == crate::JUSTINFAN1234 && self.token == crate::JUSTINFAN1234
    }
}

/// User config error returned by the [UserConfigBuilder]

#[non_exhaustive]
#[derive(Debug, Copy, Clone)]
pub enum UserConfigError {
    /// An invalid name was provided

    InvalidName,
    /// An invalid token was provided.

    InvalidToken,
    /// Anonymous login was requested with a user-provided name or token

    PartialAnonymous,
}

impl std::fmt::Display for UserConfigError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::InvalidName => f.write_str("invalid name"),
            Self::InvalidToken => {
                f.write_str("invalid token. token must start with oauth: and be 36 characters")
            }
            Self::PartialAnonymous => f.write_str(
                "user provided name or token provided when an anonymous login was requested",
            ),
        }
    }
}

impl std::error::Error for UserConfigError {}

/// Builder for making a [UserConfig]

#[derive(Default, Debug)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct UserConfigBuilder {
    capabilities: BTreeSet<Capability>,
    name: Option<String>,
    token: Option<String>,
}

impl UserConfigBuilder {
    /// Name for the connection

    pub fn name(mut self, name: impl ToString) -> Self {
        self.name.replace(name.to_string());
        self
    }

    /// Token for the connection

    ///

    /// This is an oauth token. It must have atleast two [scopes]: `chat:read`, `chat:edit`

    ///

    /// [scopes]: https://dev.twitch.tv/docs/authentication/#scopes

    pub fn token(mut self, token: impl ToString) -> Self {
        self.token.replace(token.to_string());
        self
    }

    /// Uses an anonymous login

    ///

    /// This uses `"justin1234"` as the name and token

    ///

    pub fn anonymous(self) -> Self {
        let (name, token) = crate::ANONYMOUS_LOGIN;
        self.name(name).token(token)
    }

    /// Capabilities to enable

    ///

    pub fn capabilities(mut self, caps: &[Capability]) -> Self {
        self.capabilities.extend(caps);
        self
    }

    /// Enables all of the capabilities.

    ///

    /// This is just a shortcut for enabling all of the Capabilities listed [here].

    ///

    /// [here]: Capability

    pub fn enable_all_capabilities(self) -> Self {
        self.capabilities(&[
            Capability::Membership,
            Capability::Tags,
            Capability::Commands,
        ])
    }

    /// Tries to build the UserConfig

    ///

    /// This returns an error if the name or token are invalid

    ///

    /// If the anonymous `name` OR `token` is used without the other matching one this will return an [error].

    ///

    /// [error]: UserConfigError

    pub fn build(self) -> Result<UserConfig, UserConfigError> {
        let name = self
            .name
            .filter(|s| validate_name(s))
            .ok_or(UserConfigError::InvalidName)?;

        let token = self
            .token
            .filter(|s| validate_token(s))
            .ok_or(UserConfigError::InvalidToken)?;

        match (name.as_str(), token.as_str()) {
            (crate::JUSTINFAN1234, crate::JUSTINFAN1234) => {
                // both are allowed

            }
            (crate::JUSTINFAN1234, ..) | (.., crate::JUSTINFAN1234) => {
                return Err(UserConfigError::PartialAnonymous)
            }
            _ => {}
        }

        Ok(UserConfig {
            name,
            token,
            capabilities: self.capabilities.into_iter().collect(),
        })
    }
}

#[inline]
const fn validate_name(s: &str) -> bool {
    !s.is_empty()
}

#[inline]
fn validate_token(s: &str) -> bool {
    if s == crate::JUSTINFAN1234 {
        return true;
    }
    !s.is_empty() && s.len() == 36 && &s[..6] == "oauth:"
}

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

    #[test]
    fn valid_user_config_no_caps() {
        let config = UserConfig::builder()
            .name("foo")
            .token(format!("oauth:{}", "a".repeat(30)))
            .build()
            .unwrap();

        assert_eq!(
            config,
            UserConfig {
                name: "foo".to_string(),
                token: format!("oauth:{}", "a".repeat(30)),
                capabilities: vec![],
            }
        )
    }

    #[test]
    fn valid_user_config() {
        let config = UserConfig::builder()
            .name("foo")
            .token(format!("oauth:{}", "a".repeat(30)))
            .capabilities(&[Capability::Tags, Capability::Tags])
            .capabilities(&[Capability::Membership])
            .build()
            .unwrap();

        assert_eq!(
            config,
            UserConfig {
                name: "foo".to_string(),
                token: format!("oauth:{}", "a".repeat(30)),
                capabilities: vec![Capability::Membership, Capability::Tags,],
            }
        )
    }

    #[test]
    fn valid_user_config_anonymous() {
        let config = UserConfig::builder().anonymous().build().unwrap();

        assert_eq!(
            config,
            UserConfig {
                name: crate::JUSTINFAN1234.to_string(),
                token: crate::JUSTINFAN1234.to_string(),
                capabilities: vec![],
            }
        );

        assert!(config.is_anonymous());
    }

    #[test]
    fn invalid_name_missing() {
        let err = UserConfig::builder().build().unwrap_err();
        matches!(err, UserConfigError::InvalidName);
    }

    #[test]
    fn invalid_partial_login_name() {
        let err = UserConfig::builder()
            .anonymous()
            .name("foo")
            .build()
            .unwrap_err();
        matches!(err, UserConfigError::PartialAnonymous);
    }

    #[test]
    fn invalid_partial_login_token() {
        let err = UserConfig::builder()
            .anonymous()
            .token(format!("oauth:{}", "a".repeat(30)))
            .build()
            .unwrap_err();
        matches!(err, UserConfigError::PartialAnonymous);
    }

    #[test]
    fn invalid_token_missing() {
        let err = UserConfig::builder().name("foobar").build().unwrap_err();
        matches!(err, UserConfigError::InvalidToken);
    }

    #[test]
    fn invalid_token_empty() {
        let err = UserConfig::builder()
            .name("foobar")
            .token("")
            .build()
            .unwrap_err();
        matches!(err, UserConfigError::InvalidToken);
    }

    #[test]
    fn invalid_token_short() {
        let err = UserConfig::builder()
            .name("foobar")
            .token("foo")
            .build()
            .unwrap_err();
        matches!(err, UserConfigError::InvalidToken);
    }

    #[test]
    fn invalid_token_no_oauth() {
        let err = UserConfig::builder()
            .name("foobar")
            .token("a".repeat(36))
            .build()
            .unwrap_err();
        matches!(err, UserConfigError::InvalidToken);
    }
}