//! The SoulStream holdings contract. Single writer: one member's latest
//! signed album list in one Space, at the address (space id, member key).
//! Merge is the pointer contract's total order, (sequence, blake3) —
//! `persona_state::holdings::merge` decides, so every delivery order
//! converges, and a stale replay cannot bring a withdrawn list back.
//!
//! The body is opaque here: sealed to the room's epoch key in a private
//! Space, and the contract only ever checks the envelope and its signature.
//!
//! Build: `cargo build --release --target wasm32-unknown-unknown` in this
//! directory; copy `target/wasm32-unknown-unknown/release/
//! soulstream_holdings_contract.wasm` to `src-tauri/assets/holdings_contract.wasm`
//! and re-pin the code hash in `src-tauri/src/holdings.rs`.

use freenet_stdlib::prelude::*;
use persona_state::holdings as t;

pub struct Contract;

fn parts(parameters: &Parameters<'static>) -> Result<([u8; 16], [u8; 32]), ContractError> {
    t::params_parts(parameters.as_ref())
        .ok_or_else(|| ContractError::Other("params are not family+space+member".into()))
}

fn summary_of(bytes: &[u8], s: &t::HoldingsState) -> Vec<u8> {
    let (seq, hash) = t::rank(bytes, s);
    let mut out = Vec::with_capacity(40);
    out.extend_from_slice(&seq.to_le_bytes());
    out.extend_from_slice(&hash);
    out
}

#[contract]
impl ContractInterface for Contract {
    fn validate_state(
        parameters: Parameters<'static>,
        state: State<'static>,
        _related: RelatedContracts<'static>,
    ) -> Result<ValidateResult, ContractError> {
        let (space_id, member) = parts(&parameters)?;
        if state.as_ref().is_empty() {
            return Ok(ValidateResult::Valid);
        }
        match t::validate(&space_id, &member, state.as_ref()) {
            Ok(_) => Ok(ValidateResult::Valid),
            Err(e) => Err(ContractError::Other(format!("invalid holdings: {e}"))),
        }
    }

    fn update_state(
        parameters: Parameters<'static>,
        state: State<'static>,
        data: Vec<UpdateData<'static>>,
    ) -> Result<UpdateModification<'static>, ContractError> {
        let (space_id, member) = parts(&parameters)?;
        let mut candidates: Vec<Vec<u8>> = Vec::new();
        if !state.as_ref().is_empty() {
            candidates.push(state.as_ref().to_vec());
        }
        let mut incoming_valid = 0usize;
        for ud in &data {
            let mut push = |bytes: &[u8]| {
                if bytes.is_empty() {
                    return;
                }
                if t::validate(&space_id, &member, bytes).is_ok() {
                    incoming_valid += 1;
                }
                candidates.push(bytes.to_vec());
            };
            match ud {
                UpdateData::State(s) => push(s.as_ref()),
                UpdateData::Delta(d) => push(d.as_ref()),
                UpdateData::StateAndDelta { state, delta } => {
                    push(state.as_ref());
                    push(delta.as_ref());
                }
                _ => {}
            }
        }
        if incoming_valid == 0 && !data.is_empty() {
            return Err(ContractError::InvalidUpdate);
        }
        match t::merge(&space_id, &member, candidates.iter().map(|v| v.as_slice())) {
            Some(bytes) => Ok(UpdateModification::valid(State::from(bytes))),
            None => Ok(UpdateModification::valid(state)),
        }
    }

    fn summarize_state(
        parameters: Parameters<'static>,
        state: State<'static>,
    ) -> Result<StateSummary<'static>, ContractError> {
        let (space_id, member) = parts(&parameters)?;
        if state.as_ref().is_empty() {
            return Ok(StateSummary::from(Vec::new()));
        }
        let s = t::validate(&space_id, &member, state.as_ref())
            .map_err(|e| ContractError::Other(format!("invalid holdings: {e}")))?;
        Ok(StateSummary::from(summary_of(state.as_ref(), &s)))
    }

    fn get_state_delta(
        parameters: Parameters<'static>,
        state: State<'static>,
        summary: StateSummary<'static>,
    ) -> Result<StateDelta<'static>, ContractError> {
        let (space_id, member) = parts(&parameters)?;
        if state.as_ref().is_empty() {
            return Ok(StateDelta::from(Vec::new()));
        }
        let s = t::validate(&space_id, &member, state.as_ref())
            .map_err(|e| ContractError::Other(format!("invalid holdings: {e}")))?;
        let ours = t::rank(state.as_ref(), &s);
        let theirs = {
            let b = summary.as_ref();
            if b.len() == 40 {
                let seq = u64::from_le_bytes(b[..8].try_into().unwrap());
                let mut h = [0u8; 32];
                h.copy_from_slice(&b[8..40]);
                Some((seq, h))
            } else {
                None
            }
        };
        let newer = match theirs {
            Some(t) => ours > t,
            None => true,
        };
        Ok(StateDelta::from(if newer { state.as_ref().to_vec() } else { Vec::new() }))
    }
}