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use anyhow::Context;
#[cfg(feature = "fs")]
use mithril_common::digesters::{CardanoImmutableDigester, ImmutableDigester};
use mithril_common::entities::{ProtocolMessage, ProtocolMessagePartKey};
use mithril_common::messages::SignerWithStakeMessagePart;
use mithril_common::protocol::SignerBuilder;
use slog::{o, Logger};
#[cfg(feature = "fs")]
use std::path::Path;
#[cfg(feature = "fs")]
use std::sync::Arc;

#[cfg(feature = "fs")]
use crate::MithrilCertificate;
use crate::{MithrilResult, MithrilStakeDistribution};

/// A [MessageBuilder] can be used to compute the message of Mithril artifacts.
pub struct MessageBuilder {
    #[cfg(feature = "fs")]
    immutable_digester: Option<Arc<dyn ImmutableDigester>>,
    logger: Logger,
}

impl MessageBuilder {
    /// Constructs a new `MessageBuilder`.
    pub fn new() -> MessageBuilder {
        let logger = Logger::root(slog::Discard, o!());
        Self {
            #[cfg(feature = "fs")]
            immutable_digester: None,
            logger,
        }
    }

    /// Set the [Logger] to use.
    pub fn with_logger(mut self, logger: Logger) -> Self {
        self.logger = logger;
        self
    }

    cfg_fs! {
    fn get_immutable_digester(&self) -> Arc<dyn ImmutableDigester> {
        match self.immutable_digester.as_ref() {
            None => Arc::new(CardanoImmutableDigester::new(None, self.logger.clone())),
            Some(digester) => digester.clone(),
        }
    }

    /// Set the [ImmutableDigester] to be used for the message computation for snapshot.
    ///
    /// If not set a default implementation will be used.
    pub fn with_immutable_digester(
        mut self,
        immutable_digester: Arc<dyn ImmutableDigester>,
    ) -> Self {
        self.immutable_digester = Some(immutable_digester);
        self
    }

    /// Compute message for a snapshot (based on the directory where it was unpacked).
    ///
    /// Warning: this operation can be quite long depending on the snapshot size.
    pub async fn compute_snapshot_message(
        &self,
        snapshot_certificate: &MithrilCertificate,
        unpacked_snapshot_directory: &Path,
    ) -> MithrilResult<ProtocolMessage> {
        let digester = self.get_immutable_digester();

        let mut message = snapshot_certificate.protocol_message.clone();

        let digest = digester
            .compute_digest(unpacked_snapshot_directory, &snapshot_certificate.beacon)
            .await
            .with_context(|| {
                format!(
                    "Snapshot digest computation failed: unpacked_dir: '{}'",
                    unpacked_snapshot_directory.display()
                )
            })?;
        message.set_message_part(ProtocolMessagePartKey::SnapshotDigest, digest);

        Ok(message)
    }
    }

    /// Compute message for a Mithril stake distribution.
    pub fn compute_mithril_stake_distribution_message(
        &self,
        mithril_stake_distribution: &MithrilStakeDistribution,
    ) -> MithrilResult<ProtocolMessage> {
        let signers = SignerWithStakeMessagePart::try_into_signers(
            mithril_stake_distribution.signers_with_stake.clone(),
        )
        .with_context(|| "Could not compute message: conversion failure")?;

        let signer_builder =
            SignerBuilder::new(&signers, &mithril_stake_distribution.protocol_parameters)
                .with_context(|| {
                    "Could not compute message: aggregate verification key computation failed"
                })?;

        let avk = signer_builder
            .compute_aggregate_verification_key()
            .to_json_hex()
            .with_context(|| {
                "Could not compute message: aggregate verification key encoding failed"
            })?;

        let mut message = ProtocolMessage::new();
        message.set_message_part(ProtocolMessagePartKey::NextAggregateVerificationKey, avk);

        Ok(message)
    }
}

impl Default for MessageBuilder {
    fn default() -> Self {
        Self::new()
    }
}