//! Contains the data structures related to event  to send to approvers, or to validators if approval is not required.
use std::collections::HashSet;

use crate::{
    commons::{
        crypto::{KeyMaterial, KeyPair},
        errors::SubjectError,
    },
    identifier::{DigestIdentifier, KeyIdentifier},
    request::EventRequest,
    signature::{Signature, Signed},
    ApprovalResponse, Derivable, EvaluationRequest, EvaluationResponse,
};
use borsh::{BorshDeserialize, BorshSerialize};
use json_patch::diff;
use serde::{Deserialize, Serialize};
use serde_json::json;

use super::{
    approval::ApprovalRequest, evaluation::SubjectContext, state::generate_subject_id,
    value_wrapper::ValueWrapper, HashId,
};

/// A struct representing an event.
#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, BorshSerialize, BorshDeserialize)]
pub struct Event {
    /// The identifier of the subject of the event.
    pub subject_id: DigestIdentifier,
    /// The signed event request.
    pub event_request: Signed<EventRequest>,
    /// The sequence number of the event.
    pub sn: u64,
    /// The version of the governance contract.
    pub gov_version: u64,
    /// The patch to apply to the state.
    pub patch: ValueWrapper,
    /// The hash of the state after applying the patch.
    pub state_hash: DigestIdentifier,
    /// Whether the evaluation was successful and the result was validated against the schema.
    pub eval_success: bool,
    /// Whether approval is required for the event to be applied to the state.
    pub appr_required: bool,
    /// Whether the event has been approved.
    pub approved: bool,
    /// The hash of the previous event.
    pub hash_prev_event: DigestIdentifier,
    /// The set of evaluators who have evaluated the event.
    pub evaluators: HashSet<Signature>,
    /// The set of approvers who have approved the event.
    pub approvers: HashSet<Signature>,
}

impl Event {
    pub(crate) fn get_approval_hash(
        &self,
        gov_id: DigestIdentifier,
    ) -> Result<DigestIdentifier, SubjectError> {
        ApprovalRequest {
            event_request: self.event_request.clone(),
            sn: self.sn,
            gov_version: self.gov_version,
            patch: self.patch.clone(),
            state_hash: self.state_hash.clone(),
            hash_prev_event: self.hash_prev_event.clone(),
            gov_id,
        }
        .hash_id()
    }
}

impl HashId for Event {
    fn hash_id(&self) -> Result<DigestIdentifier, SubjectError> {
        DigestIdentifier::from_serializable_borsh(&self)
            .map_err(|_| SubjectError::SignatureCreationFails("HashId for Event Fails".to_string()))
    }
}

impl HashId for Signed<Event> {
    fn hash_id(&self) -> Result<DigestIdentifier, SubjectError> {
        DigestIdentifier::from_serializable_borsh(&self).map_err(|_| {
            SubjectError::SignatureCreationFails("HashId for Signed Event Fails".to_string())
        })
    }
}

impl Signed<Event> {
    pub fn from_genesis_request(
        event_request: Signed<EventRequest>,
        subject_keys: &KeyPair,
        gov_version: u64,
        init_state: &ValueWrapper,
    ) -> Result<Self, SubjectError> {
        let EventRequest::Create(start_request) = event_request.content.clone() else {
            return Err(SubjectError::NotCreateEvent)
        };
        let json_patch = serde_json::to_value(diff(&json!({}), &init_state.0)).map_err(|_| {
            SubjectError::CryptoError(String::from("Error converting patch to value"))
        })?;
        let public_key = KeyIdentifier::new(
            subject_keys.get_key_derivator(),
            &subject_keys.public_key_bytes(),
        );
        let subject_id = generate_subject_id(
            &start_request.namespace,
            &start_request.schema_id,
            public_key.to_str(),
            start_request.governance_id.to_str(),
            gov_version,
        )?;
        let state_hash = DigestIdentifier::from_serializable_borsh(init_state).map_err(|_| {
            SubjectError::CryptoError(String::from("Error converting state to hash"))
        })?;
        let content = Event {
            subject_id,
            event_request,
            sn: 0,
            gov_version,
            patch: ValueWrapper(json_patch),
            state_hash,
            eval_success: true,
            appr_required: false,
            approved: true,
            hash_prev_event: DigestIdentifier::default(),
            evaluators: HashSet::new(),
            approvers: HashSet::new(),
        };
        let subject_signature_event = Signature::new(&content, public_key.clone(), &subject_keys)
            .map_err(|_| {
            SubjectError::CryptoError(String::from("Error signing the hash of the proposal"))
        })?;
        Ok(Self {
            content,
            signature: subject_signature_event,
        })
    }

    pub fn verify_signatures(&self) -> Result<(), SubjectError> {
        // Verify event and event_request signatures
        self.signature.verify(&self.content)?;
        self.content.event_request.verify()
    }

    pub fn verify_eval_appr(
        &self,
        subject_context: SubjectContext,
        eval_sign_info: (&HashSet<KeyIdentifier>, u32, u32),
        appr_sign_info: (&HashSet<KeyIdentifier>, u32, u32),
    ) -> Result<(), SubjectError> {
        if !self.content.event_request.content.requires_eval_appr()
            && self.content.eval_success
            && self.content.approved
            && !self.content.appr_required
        {
            return Ok(());
        }
        let gov_id = subject_context.governance_id.clone();
        // Verify evaluators signatures
        let eval_request = EvaluationRequest {
            event_request: self.content.event_request.clone(),
            context: subject_context,
            sn: self.content.sn,
            gov_version: self.content.gov_version,
        };
        let eval_response = EvaluationResponse {
            patch: self.content.patch.clone(), // Esto no hace falta realmente
            eval_req_hash: eval_request.hash_id()?,
            state_hash: self.content.state_hash.clone(),
            eval_success: self.content.eval_success,
            appr_required: self.content.appr_required,
        };
        let mut evaluators = HashSet::new();
        for eval_signature in self.content.evaluators.iter() {
            if !evaluators.insert(eval_signature.signer.clone()) {
                return Err(SubjectError::RepeatedSignature(
                    "Repeated Signer in Evaluators".to_string(),
                ));
            }
            eval_signature.verify(&eval_response)?;
        }
        if !evaluators.is_subset(eval_sign_info.0) {
            return Err(SubjectError::SignersError(
                "Incorrect Evaluators signed".to_string(),
            ));
        }
        let quorum_size_eval = if self.content.eval_success {
            eval_sign_info.1
        } else {
            eval_sign_info.2
        };
        if evaluators.len() < quorum_size_eval as usize {
            return Err(SubjectError::SignersError(
                "Not enough Evaluators signed".to_string(),
            ));
        }
        if self.content.approved && !self.content.appr_required {
            return Ok(());
        }
        // Verify approvers signatures
        let appr_request = ApprovalRequest {
            event_request: self.content.event_request.clone(),
            sn: self.content.sn,
            gov_version: self.content.gov_version,
            patch: self.content.patch.clone(),
            state_hash: self.content.state_hash.clone(),
            hash_prev_event: self.content.hash_prev_event.clone(),
            gov_id,
        };
        let appr_response = ApprovalResponse {
            appr_req_hash: appr_request.hash_id()?,
            approved: self.content.approved,
        };
        let mut approvers = HashSet::new();
        for appr_signature in self.content.approvers.iter() {
            if !approvers.insert(appr_signature.signer.clone()) {
                return Err(SubjectError::RepeatedSignature(
                    "Repeated Signer in Approvers".to_string(),
                ));
            }
            appr_signature.verify(&appr_response)?;
        }
        if !approvers.is_subset(appr_sign_info.0) {
            return Err(SubjectError::SignersError(
                "Incorrect Approvers signed".to_string(),
            ));
        }
        let quorum_size_appr = if self.content.approved {
            appr_sign_info.1
        } else {
            appr_sign_info.2
        };
        if approvers.len() < quorum_size_appr as usize {
            return Err(SubjectError::SignersError(
                "Not enough Approvers signed".to_string(),
            ));
        }
        Ok(())
    }
}

/// A struct representing the metadata of a TAPLE event.
#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, BorshSerialize, BorshDeserialize)]
pub struct Metadata {
    /// The namespace of the event.
    pub namespace: String,
    /// The identifier of the subject of the event.
    pub subject_id: DigestIdentifier,
    /// The identifier of the governance contract.
    pub governance_id: DigestIdentifier,
    /// The version of the governance contract.
    pub governance_version: u64,
    /// The identifier of the schema used to validate the event.
    pub schema_id: String,
}