use std::collections::HashMap;

use pallas_addresses::{Address, ScriptHash, ShelleyPaymentPart, StakePayload};
use pallas_codec::utils::{KeyValuePairs, MaybeIndefArray};
use pallas_primitives::babbage::{
    Certificate, MintedTx, PolicyId, RedeemerTag, RewardAccount, StakeCredential, TransactionOutput,
};

use super::{
    error::Error,
    eval::{DataLookupTable, ScriptVersion},
    script_context::{ResolvedInput, ScriptPurpose},
};

// TODO: include in pallas eventually?
#[derive(Debug, PartialEq, Clone)]
struct RedeemerPtr {
    tag: RedeemerTag,
    index: u32,
}

type AlonzoScriptsNeeded = Vec<(ScriptPurpose, ScriptHash)>;

// subset of phase-1 ledger checks related to scripts
pub fn eval_phase_one(
    tx: &MintedTx,
    utxos: &[ResolvedInput],
    lookup_table: &DataLookupTable,
) -> Result<(), Error> {
    let scripts_needed = scripts_needed(tx, utxos)?;

    validate_missing_scripts(&scripts_needed, lookup_table.scripts())?;

    has_exact_set_of_redeemers(tx, &scripts_needed, lookup_table.scripts())?;

    Ok(())
}

pub fn validate_missing_scripts(
    needed: &AlonzoScriptsNeeded,
    txscripts: HashMap<ScriptHash, ScriptVersion>,
) -> Result<(), Error> {
    let received_hashes = txscripts.keys().copied().collect::<Vec<ScriptHash>>();

    let needed_hashes = needed.iter().map(|x| x.1).collect::<Vec<ScriptHash>>();

    let missing: Vec<_> = needed_hashes
        .clone()
        .into_iter()
        .filter(|x| !received_hashes.contains(x))
        .map(|x| format!("[Missing (sh: {})]", x))
        .collect();

    let extra: Vec<_> = received_hashes
        .into_iter()
        .filter(|x| !needed_hashes.contains(x))
        .map(|x| format!("[Extraneous (sh: {:?})]", x))
        .collect();

    if !missing.is_empty() || !extra.is_empty() {
        let missing_errors = missing.join(" ");
        let extra_errors = extra.join(" ");

        unreachable!(
            "Mismatch in required scripts: {} {}",
            missing_errors, extra_errors
        );
    }

    Ok(())
}

pub fn scripts_needed(
    tx: &MintedTx,
    utxos: &[ResolvedInput],
) -> Result<AlonzoScriptsNeeded, Error> {
    let mut needed = Vec::new();

    let txb = tx.transaction_body.clone();

    let mut spend = Vec::new();

    for input in txb.inputs.iter() {
        let utxo = match utxos.iter().find(|utxo| utxo.input == *input) {
            Some(u) => u,
            None => return Err(Error::ResolvedInputNotFound),
        };

        let address = Address::from_bytes(match &utxo.output {
            TransactionOutput::Legacy(output) => output.address.as_ref(),
            TransactionOutput::PostAlonzo(output) => output.address.as_ref(),
        })?;

        if let Address::Shelley(a) = address {
            if let ShelleyPaymentPart::Script(h) = a.payment() {
                spend.push((ScriptPurpose::Spending(input.clone()), *h));
            }
        }
    }

    let mut reward = txb
        .withdrawals
        .as_ref()
        .unwrap_or(&KeyValuePairs::Indef(vec![]))
        .iter()
        .map(|(acnt, _)| {
            let address = Address::from_bytes(acnt).unwrap();

            if let Address::Stake(a) = address {
                if let StakePayload::Script(h) = a.payload() {
                    let cred = StakeCredential::Scripthash(*h);
                    return Some((ScriptPurpose::Rewarding(cred), *h));
                }
            }

            None
        })
        .flatten()
        .collect::<AlonzoScriptsNeeded>();

    let mut cert = txb
        .certificates
        .clone()
        .unwrap_or_default()
        .iter()
        .map(|cert| {
            // only Dereg and Deleg certs can require scripts
            match cert {
                Certificate::StakeDeregistration(StakeCredential::Scripthash(h)) => {
                    Some((ScriptPurpose::Certifying(cert.clone()), *h))
                }
                Certificate::StakeDelegation(StakeCredential::Scripthash(h), _) => {
                    Some((ScriptPurpose::Certifying(cert.clone()), *h))
                }
                _ => None,
            }
        })
        .flatten()
        .collect::<AlonzoScriptsNeeded>();

    let mut mint = txb
        .mint
        .as_ref()
        .unwrap_or(&KeyValuePairs::Indef(vec![]))
        .iter()
        .map(|(policy_id, _)| (ScriptPurpose::Minting(*policy_id), *policy_id))
        .collect::<AlonzoScriptsNeeded>();

    needed.append(&mut spend);
    needed.append(&mut reward);
    needed.append(&mut cert);
    needed.append(&mut mint);

    Ok(needed)
}

/// hasExactSetOfRedeemers in Ledger Spec, but we pass `txscripts` directly
pub fn has_exact_set_of_redeemers(
    tx: &MintedTx,
    needed: &AlonzoScriptsNeeded,
    tx_scripts: HashMap<ScriptHash, ScriptVersion>,
) -> Result<(), Error> {
    let mut redeemers_needed = Vec::new();

    for (script_purpose, script_hash) in needed {
        let redeemer_ptr = build_redeemer_ptr(tx, script_purpose)?;
        let script = tx_scripts.get(script_hash);

        if let (Some(ptr), Some(script)) = (redeemer_ptr, script) {
            match script {
                ScriptVersion::V1(_) => {
                    redeemers_needed.push((ptr, script_purpose.clone(), *script_hash))
                }
                ScriptVersion::V2(_) => {
                    redeemers_needed.push((ptr, script_purpose.clone(), *script_hash))
                }
                ScriptVersion::Native(_) => (),
            }
        }
    }

    let wits_redeemer_ptrs: Vec<RedeemerPtr> = tx
        .transaction_witness_set
        .redeemer
        .as_ref()
        .unwrap_or(&MaybeIndefArray::Indef(vec![]))
        .iter()
        .map(|r| RedeemerPtr {
            tag: r.tag.clone(),
            index: r.index,
        })
        .collect();

    let needed_redeemer_ptrs: Vec<RedeemerPtr> =
        redeemers_needed.iter().map(|x| x.0.clone()).collect();

    let missing: Vec<_> = redeemers_needed
        .into_iter()
        .filter(|x| !wits_redeemer_ptrs.contains(&x.0))
        .map(|x| {
            format!(
                "[Missing (redeemer_ptr: {:?}, script_purpose: {:?}, script_hash: {})]",
                x.0, x.1, x.2,
            )
        })
        .collect();

    let extra: Vec<_> = wits_redeemer_ptrs
        .into_iter()
        .filter(|x| !needed_redeemer_ptrs.contains(x))
        .map(|x| format!("[Extraneous (redeemer_ptr: {:?})]", x))
        .collect();

    if !missing.is_empty() || !extra.is_empty() {
        Err(Error::RequiredRedeemersMismatch { missing, extra })
    } else {
        Ok(())
    }
}

/// builds a redeemer pointer (tag, index) from a script purpose by setting the tag
/// according to the type of the script purpose, and the index according to the
/// placement of script purpose inside its container.
fn build_redeemer_ptr(
    tx: &MintedTx,
    script_purpose: &ScriptPurpose,
) -> Result<Option<RedeemerPtr>, Error> {
    let tx_body = tx.transaction_body.clone();

    match script_purpose {
        ScriptPurpose::Minting(hash) => {
            let mut policy_ids = tx_body
                .mint
                .as_ref()
                .unwrap_or(&KeyValuePairs::Indef(vec![]))
                .iter()
                .map(|(policy_id, _)| *policy_id)
                .collect::<Vec<PolicyId>>();

            policy_ids.sort();

            let maybe_idx = policy_ids.iter().position(|x| x == hash);

            match maybe_idx {
                Some(idx) => Ok(Some(RedeemerPtr {
                    tag: RedeemerTag::Mint,
                    index: idx as u32,
                })),
                None => Ok(None),
            }
        }
        ScriptPurpose::Spending(txin) => {
            let mut inputs = tx_body.inputs.to_vec();
            inputs.sort_by(
                |i_a, i_b| match i_a.transaction_id.cmp(&i_b.transaction_id) {
                    std::cmp::Ordering::Less => std::cmp::Ordering::Less,
                    std::cmp::Ordering::Equal => i_a.index.cmp(&i_b.index),
                    std::cmp::Ordering::Greater => std::cmp::Ordering::Greater,
                },
            );

            let maybe_idx = inputs.iter().position(|x| x == txin);

            match maybe_idx {
                Some(idx) => Ok(Some(RedeemerPtr {
                    tag: RedeemerTag::Spend,
                    index: idx as u32,
                })),
                None => Ok(None),
            }
        }
        ScriptPurpose::Rewarding(racnt) => {
            let mut reward_accounts = tx_body
                .withdrawals
                .as_ref()
                .unwrap_or(&KeyValuePairs::Indef(vec![]))
                .iter()
                .map(|(acnt, _)| acnt.clone())
                .collect::<Vec<RewardAccount>>();

            reward_accounts.sort();

            let mut maybe_idx = None;

            for (idx, x) in reward_accounts.iter().enumerate() {
                let cred = match Address::from_bytes(x).unwrap() {
                    Address::Stake(a) => match a.payload() {
                        StakePayload::Script(sh) => StakeCredential::Scripthash(*sh),
                        StakePayload::Stake(_) => {
                            return Err(Error::ScriptKeyHash);
                        }
                    },
                    _ => return Err(Error::BadWithdrawalAddress),
                };

                if cred == *racnt {
                    maybe_idx = Some(idx);
                }
            }

            match maybe_idx {
                Some(idx) => Ok(Some(RedeemerPtr {
                    tag: RedeemerTag::Reward,
                    index: idx as u32,
                })),
                None => Ok(None),
            }
        }
        ScriptPurpose::Certifying(d) => {
            let maybe_idx = tx_body
                .certificates
                .as_ref()
                .unwrap_or(&MaybeIndefArray::Indef(vec![]))
                .iter()
                .position(|x| x == d);

            match maybe_idx {
                Some(idx) => Ok(Some(RedeemerPtr {
                    tag: RedeemerTag::Cert,
                    index: idx as u32,
                })),
                None => Ok(None),
            }
        }
    }
}