use std::any::Any;
use std::collections::BTreeMap;
use std::error::Error;
use std::fmt::{Debug, Display};
use std::str::FromStr;

use crate::capabilities::{CapabilityRegistry, URN_JMAP_CORE};
use crate::types::*;
use serde::{Deserialize, Serialize};

// TODO: Move to an error module
pub type JMAPResult<T> = Result<T, JMAPError>;

#[derive(Debug)]
pub enum JMAPError {
    ParseError(String),
    DowncastError(String),
    UnknownCapability(String),
    UnknownMethod(String),
    InvalidObject(String),
}

impl Display for JMAPError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:?}", self) //TODO: Make this less bad  
    }
}

impl Error for JMAPError {}

#[derive(Clone, PartialEq, PartialOrd, Ord, Eq, Debug)]
pub struct JMAPMethodName {
    pub resource: String,
    pub method: String,
}

impl JMAPMethodName {
    pub fn new(resource: String, method: String) -> Self {
        assert_ne!(resource.len(), 0);
        assert_ne!(method.len(), 0);
        Self { resource, method }
    }
}

impl FromStr for JMAPMethodName {
    type Err = JMAPError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut spl = s.split("/");

        let resource = spl
            .next()
            .expect("Always at least one string expected from `split`")
            .to_string();

        let method = (match spl.next() {
            Some(m) => {
                if m.is_empty() {
                    Err(JMAPError::ParseError(
                        "Missing method name after '/'".to_string(),
                    ))
                } else {
                    Ok(m)
                }
            }
            None => Err(JMAPError::ParseError("Missing '/' delimiter".to_string())),
        })?
        .to_string();

        if let Some(t) = spl.next() {
            Err(JMAPError::ParseError(format!(
                "Additional '/' found => '/{}'",
                t
            )))
        } else {
            Ok(Self { resource, method })
        }
    }
}

impl Display for JMAPMethodName {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}/{}", self.resource, self.method)
    }
}

#[derive(Serialize, Deserialize, Clone)]
pub struct InvocationRaw(String, JObject, String);

pub trait JMAPInvocationArg: 'static + Sized {
    const CAP_URN: &str;
    const METHOD_HINT: &'static str;
    fn from_obj(obj: &JObject) -> JMAPResult<Self>;
    fn from_obj_dyn(obj: &JObject) -> JMAPResult<Box<dyn JMAPInvocationArgDyn>> {
        let arg = Self::from_obj(obj)?;
        Ok(Box::new(arg))
    }
    fn into_obj(self) -> JMAPResult<JObject>;

    fn from_dyn(d: Box<dyn JMAPInvocationArgDyn>) -> JMAPResult<Box<Self>> {
        let dyn_hint = d.get_method_hint();
        if dyn_hint != Self::METHOD_HINT {
            return Err(JMAPError::DowncastError(format!(
                "Incompatible arguments: {} vs. {} ",
                Self::METHOD_HINT,
                dyn_hint
            )));
        }

        let rf = Box::leak(d);
        if let Some(anyref) = rf.as_any_mut().downcast_mut() {
            // Safe because the reference is leaked from another box
            unsafe { Ok(Box::from_raw(anyref)) }
        } else {
            // Safe because the reference is leaked from another box
            unsafe {
                // Free the memory
                let b = Box::from_raw(rf);
                drop(b)
            }
            Err(JMAPError::DowncastError(
                "T is not the correct type despite having same method hint".to_string(),
            ))
        }
    }
}

pub trait JMAPInvocationArgDyn: 'static {
    fn get_urn(&self) -> &'static str;
    fn get_method_hint(&self) -> &'static str;
    fn into_obj(self: Box<Self>) -> JMAPResult<JObject>;

    // Convert to any for downcasting, immutable
    fn as_any(&self) -> &dyn Any;

    /// Convert to any for downcasting, mutable
    fn as_any_mut(&mut self) -> &mut dyn Any;

    /// Convert to any for downcasting, consumes object
    fn to_any(self) -> Box<dyn Any>;
}

impl<T: JMAPInvocationArg> JMAPInvocationArgDyn for T {
    fn get_urn(&self) -> &'static str {
        T::CAP_URN
    }
    fn get_method_hint(&self) -> &'static str {
        T::METHOD_HINT
    }
    fn into_obj(self: Box<Self>) -> JMAPResult<JObject> {
        T::into_obj(*self)
    }

    fn as_any(&self) -> &dyn Any {
        self
    }

    fn as_any_mut(&mut self) -> &mut dyn Any {
        self
    }

    fn to_any(self) -> Box<dyn Any> {
        Box::new(self)
    }
}

pub struct Invocation<T: JMAPInvocationArg> {
    pub method: JMAPMethodName,
    pub arguments: T,
    pub method_call_id: String,
}

impl<T: JMAPInvocationArg> Invocation<T> {
    pub fn to_dyn(self) -> InvocationDyn {
        InvocationDyn {
            method: self.method,
            arguments: Box::new(self.arguments),
            method_call_id: self.method_call_id,
        }
    }
    pub fn from_dyn(d: InvocationDyn) -> JMAPResult<Self> {
        Ok(Self {
            method: d.method,
            arguments: *T::from_dyn(d.arguments)?,
            method_call_id: d.method_call_id,
        })
    }
    pub fn to_raw(self) -> JMAPResult<InvocationRaw> {
        let args = self.arguments.into_obj()?; 
        Ok(InvocationRaw (
           self.method.to_string(), 
           args, 
           self.method_call_id
        ))
    }

    pub fn new(arguments: T, method_call_id: String) -> Self {
        Self {
            method: T::METHOD_HINT.parse().expect("METHOD_HINT MUST Contain a valid method name"),
            arguments, 
            method_call_id,
        }
    }
}

pub struct InvocationDyn {
    method: JMAPMethodName,
    arguments: Box<dyn JMAPInvocationArgDyn>,
    method_call_id: String,
}

impl InvocationDyn {
    pub fn to_raw(self) -> JMAPResult<InvocationRaw>{
        let args = self.arguments; 
        let args_obj = args.into_obj()?;
        Ok(InvocationRaw (
           self.method.to_string(), 
           args_obj, 
           self.method_call_id
        ))

    }
}

impl Debug for InvocationDyn {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "InvocationDyn({}, *, {})",
            self.method, self.method_call_id
        )
    }
}

#[derive(Serialize, Deserialize, Clone)]
pub struct JMAPRequestRaw {
    using: JArr<String>,
    #[serde(rename = "methodCalls")]
    method_calls: JArr<InvocationRaw>,
    #[serde(rename = "createIds")]
    #[serde(skip_serializing_if = "Option::is_none")]
    create_ids: Option<JObj<JMAPId, JMAPId>>,
}

#[derive(Debug)]
pub struct JMAPRequest {
    pub using: JArr<String>,
    pub method_calls: JArr<JMAPResult<InvocationDyn>>,
    pub create_ids: Option<JObj<JMAPId, JMAPId>>,
}

pub type MethodArgsParser = Box<fn(&JObject) -> JMAPResult<Box<dyn JMAPInvocationArgDyn>>>;
pub struct MethodRegistry(pub BTreeMap<JMAPMethodName, MethodArgsParser>);
impl Default for MethodRegistry {
    fn default() -> Self {
        Self::new()
    }
}

impl MethodRegistry {
    /// Create a collection of parsers
    pub fn new() -> Self {
        Self(BTreeMap::new())
    }

    /// Insert a parser
    pub fn add_method<T: JMAPInvocationArg>(&mut self) {
        self.0.insert(
            T::METHOD_HINT
                .parse()
                .expect("METHOD_HINT needs to be a valid Method Name"),
            Box::new(T::from_obj_dyn),
        );
    }
}

impl Default for JMAPRequest {
    fn default() -> Self {
        Self {
            using: vec![URN_JMAP_CORE.to_string()],
            method_calls: vec![],
            create_ids: None,
        }
    }
} 


impl JMAPRequest {
    pub fn from_raw(
        raw: JMAPRequestRaw,
        registry: &CapabilityRegistry,
        fail_on_unknown_capability: bool,
    ) -> JMAPResult<Self> {
        let using = raw.using;
        let create_ids = raw.create_ids;
        let mut method_registries = Vec::with_capacity(using.len());
        let mut encountered_urns = Vec::with_capacity(using.len());
        let mut has_core = false;

        for cap_urn in using.iter() {
            if cap_urn == URN_JMAP_CORE {
                has_core = true;
            }
            if encountered_urns.contains(&cap_urn) {
                return Err(JMAPError::InvalidObject(format!(
                    "Dupplicate capability {}",
                    cap_urn
                )));
            }
            encountered_urns.push(cap_urn);
            if let Some(method_reg) = registry.0.get(cap_urn) {
                method_registries.push(&method_reg.methods);
            } else if fail_on_unknown_capability {
                return Err(JMAPError::UnknownCapability(cap_urn.clone()));
            }
        }

        if !has_core {
            return Err(JMAPError::InvalidObject(
                "Missing core capability".to_string(),
            ));
        }
        let method_calls: Vec<JMAPResult<InvocationDyn>> = raw
            .method_calls
            .into_iter()
            .map(|method_call| {
                let mut method_parser_opt: Option<&MethodArgsParser> = None;
                match method_call.0.parse() {
                    Ok(method_name) => {
                        for reg in method_registries.iter() {
                            if let Some(parser) = reg.0.get(&method_name) {
                                method_parser_opt = Some(parser);
                                break;
                            }
                        }
                        if let Some(method_parser) = method_parser_opt {
                            let method_args = method_parser(&method_call.1)?;
                            Ok(InvocationDyn {
                                method: method_name,
                                arguments: method_args,
                                method_call_id: method_call.2,
                            })
                        } else {
                            Err(JMAPError::UnknownMethod(method_name.to_string()))
                        }
                    }
                    Err(err) => Err(err),
                }
            })
            .collect();

        Ok(Self {
            using,
            method_calls,
            create_ids,
        })
    }

    pub fn to_raw(self) -> JMAPResult<JMAPRequestRaw> {
        let mut method_calls = Vec::with_capacity(self.method_calls.len());
        for mcr in self.method_calls {
            let mc = mcr?;
            method_calls.push(mc.to_raw()?) 
        }
         
        Ok(JMAPRequestRaw { 
            using: self.using, 
            method_calls,
            create_ids: self.create_ids 
        })
    }  

    pub fn add_invocation<T: JMAPInvocationArg>(&mut self, invocation: Invocation<T>) -> JMAPResult<()>{
        match self.using.iter().find(|x| x.as_str() == T::CAP_URN) {
            Some(_) => {},
            None => { self.using.push(T::CAP_URN.to_string()); } // TODO: Turn into set
        }
        self.method_calls.push(Ok(invocation.to_dyn()));    
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use jiff::fmt::rfc2822::parse;
use serde_json::json;

    use super::{JMAPRequest, JMAPRequestRaw};
    use crate::capabilities::{CapabilityRegistry, CoreEchoArgs, URN_JMAP_CORE};
    use crate::request::{Invocation, InvocationDyn, JMAPError, JMAPResult};
    use crate::{JMAPId, JObject, JUnknown};
    use std::assert_matches;
    use std::str::FromStr;

    #[test]
    fn test_jmap_request_parsing() {
        let req = r#"{
            "using": ["urn:ietf:params:jmap:core", "something_unknown"], 
            "methodCalls": [
                [
                  "Core/Echo", {
                    "hello": "Hello world!" 
                  }, 
                  "a"
                ], 
                [
                  "Unknown/Get", { 
                    "something": "else"
                  },
                  "b"
                ]
            ],
            "createIds": {
                "i1": "id1"
            } 
        }"#;

        let reg = CapabilityRegistry::default();
        let raw: JMAPRequestRaw = serde_json::from_str(req).unwrap();
        let req_ok = JMAPRequest::from_raw(raw, &reg, false);
        assert_matches!(
            req_ok,
            Ok(JMAPRequest {
                using: _,
                method_calls: _,
                create_ids: _
            })
        );
        let mut req_real = req_ok.expect("We tested this before");

        assert_eq!(
            req_real
                .create_ids
                .expect("We specified this in the test")
                .get(&("i1".parse().unwrap()))
                .expect("i1 Should be included")
                .clone(),
            JMAPId::from_str("id1").unwrap()
        );

        assert_eq!(req_real.using, vec![URN_JMAP_CORE, "something_unknown"]);
        let unknown = req_real.method_calls.get(1).unwrap();
        assert_matches!(unknown, Err(JMAPError::UnknownMethod(_)));

        let echo = req_real.method_calls.remove(0).unwrap();

        let invocation: Invocation<CoreEchoArgs> = Invocation::from_dyn(echo).unwrap();

        assert_eq!(
            invocation.arguments.obj.get("hello"),
            Some(&JUnknown::String("Hello world!".to_string()))
        );
    }
    #[test] 
    fn unknown_capability() {
        let req = r#"{
            "using": ["urn:ietf:params:jmap:core", "something_unknown"], 
            "methodCalls": [
                [
                  "Core/Echo", {
                    "hello": "Hello world!" 
                  }, 
                  "a"
                ], 
                [
                  "Unknown/Get", { 
                    "something": "else"
                  },
                  "b"
                ]
            ],
            "createIds": {
                "i1": "id1"
            } 
        }"#;
        let reg = CapabilityRegistry::default();
        let raw: JMAPRequestRaw = serde_json::from_str(req).unwrap();
        let req_err = JMAPRequest::from_raw(raw.clone(), &reg, true);
        assert_matches!(req_err, JMAPResult::Err(JMAPError::UnknownCapability(_)))
    }

    #[test] 
    fn dupplicate_capability() {        
         let req = r#"{
            "using": ["urn:ietf:params:jmap:core", "urn:ietf:params:jmap:core"], 
            "methodCalls": [
                [
                  "Core/Echo", {
                    "hello": "Hello world!" 
                  }, 
                  "a"
                ] 
            ],
            "createIds": {
                "i1": "id1"
            } 
        }"#;
        let reg = CapabilityRegistry::default();
        let raw: JMAPRequestRaw = serde_json::from_str(req).unwrap();
        let req_err = JMAPRequest::from_raw(raw.clone(), &reg, true);
        assert_matches!(req_err, JMAPResult::Err(JMAPError::InvalidObject(_)))
    }

    #[test]
    fn builder() {
        let mut req = JMAPRequest::default(); 
        let content: JObject = serde_json::from_value(json!(
            {
                "hello": "Hello world!"
            }
        )).unwrap();
        let echo = CoreEchoArgs {obj: content} ; 
        let inv = Invocation::new(echo, "a".to_string()); 
        req.add_invocation(inv).unwrap();   

        let rraw = req.to_raw().unwrap(); 
        let exp = json!({
            "using": ["urn:ietf:params:jmap:core"], 
            "methodCalls": [
                [
                    "Core/Echo", 
                    {
                        "hello": "Hello world!"
                    }, 
                    "a"
                ]
            ]
        });
        assert_eq!(serde_json::to_value(&rraw).unwrap(), exp);
    }
}