//! P6a tests for the [`RecordTurn`] use case (ARCHITECTURE §19) with in-memory
//! port fakes (no real store/FS).
//!
//! Coverage:
//! - single `record`: log contains the turn; handoff `up_to == turn.id`; summary
//!   contains the turn text;
//! - incremental over two `record` calls: log order [t1, t2]; `up_to == t2.id`;
//!   summary contains both texts; **proof of incrementality** — the summarizer
//!   saw `prev = None` then `prev = Some(_)`, and `new_turns.len() == 1` on *both*
//!   calls (never 2 → the log is never fully re-read);
//! - error propagation: a store whose `append` / `save` / `load` returns a
//!   non-`NotFound` `StoreError` makes `record` return `AppError::Store(_)`;
//!   a failing `append` performs **no** `save` (no side effect after failure);
//! - isolation by `ConversationId`.

use std::collections::HashMap;
use std::sync::{Arc, Mutex};

use async_trait::async_trait;
use domain::ports::StoreError;
use domain::{
    ConversationId, ConversationLog, ConversationTurn, Handoff, HandoffStore, HandoffSummarizer,
    InputSource, TurnId, TurnRole,
};

use application::{AppError, RecordTurn};

// ---------------------------------------------------------------------------
// Deterministic constructors
// ---------------------------------------------------------------------------

fn conv_id(n: u128) -> ConversationId {
    ConversationId::from_uuid(uuid::Uuid::from_u128(n))
}

fn turn_id(n: u128) -> TurnId {
    TurnId::from_uuid(uuid::Uuid::from_u128(n))
}

fn turn(conv: ConversationId, id: TurnId, text: &str) -> ConversationTurn {
    ConversationTurn::new(id, conv, 1_000, InputSource::Human, TurnRole::Prompt, text)
}

// ---------------------------------------------------------------------------
// Fakes — Vec/Map backed, Mutex never held across an `.await`.
// ---------------------------------------------------------------------------

#[derive(Default)]
struct InMemoryConversationLog {
    threads: Mutex<HashMap<ConversationId, Vec<ConversationTurn>>>,
    /// When set, `append` returns this error instead of appending.
    fail_append: Mutex<Option<StoreError>>,
}

impl InMemoryConversationLog {
    fn failing_append(err: StoreError) -> Self {
        Self {
            threads: Mutex::new(HashMap::new()),
            fail_append: Mutex::new(Some(err)),
        }
    }

    fn thread(&self, conv: ConversationId) -> Vec<ConversationTurn> {
        self.threads
            .lock()
            .unwrap()
            .get(&conv)
            .cloned()
            .unwrap_or_default()
    }
}

#[async_trait]
impl ConversationLog for InMemoryConversationLog {
    async fn append(
        &self,
        conversation: ConversationId,
        turn: ConversationTurn,
    ) -> Result<(), StoreError> {
        if let Some(err) = self.fail_append.lock().unwrap().clone() {
            return Err(err);
        }
        self.threads
            .lock()
            .unwrap()
            .entry(conversation)
            .or_default()
            .push(turn);
        Ok(())
    }

    async fn read(
        &self,
        conversation: ConversationId,
        since: Option<TurnId>,
    ) -> Result<Vec<ConversationTurn>, StoreError> {
        let all = self.thread(conversation);
        let out = match since {
            None => all,
            Some(cursor) => {
                let pos = all.iter().position(|t| t.id == cursor);
                match pos {
                    Some(i) => all[i + 1..].to_vec(),
                    None => all,
                }
            }
        };
        Ok(out)
    }

    async fn last(
        &self,
        conversation: ConversationId,
        n: usize,
    ) -> Result<Vec<ConversationTurn>, StoreError> {
        let all = self.thread(conversation);
        let start = all.len().saturating_sub(n);
        Ok(all[start..].to_vec())
    }
}

#[derive(Default)]
struct InMemoryHandoffStore {
    store: Mutex<HashMap<ConversationId, Handoff>>,
    fail_load: Mutex<Option<StoreError>>,
    fail_save: Mutex<Option<StoreError>>,
    /// Number of completed `save` calls (used to prove no save-after-append-fail).
    saves: Mutex<usize>,
}

impl InMemoryHandoffStore {
    fn failing_load(err: StoreError) -> Self {
        Self {
            fail_load: Mutex::new(Some(err)),
            ..Self::default()
        }
    }

    fn failing_save(err: StoreError) -> Self {
        Self {
            fail_save: Mutex::new(Some(err)),
            ..Self::default()
        }
    }

    fn loaded(&self, conv: ConversationId) -> Option<Handoff> {
        self.store.lock().unwrap().get(&conv).cloned()
    }

    fn save_count(&self) -> usize {
        *self.saves.lock().unwrap()
    }
}

#[async_trait]
impl HandoffStore for InMemoryHandoffStore {
    async fn load(&self, conversation: ConversationId) -> Result<Option<Handoff>, StoreError> {
        if let Some(err) = self.fail_load.lock().unwrap().clone() {
            return Err(err);
        }
        Ok(self.store.lock().unwrap().get(&conversation).cloned())
    }

    async fn save(&self, conversation: ConversationId, handoff: Handoff) -> Result<(), StoreError> {
        if let Some(err) = self.fail_save.lock().unwrap().clone() {
            return Err(err);
        }
        self.store.lock().unwrap().insert(conversation, handoff);
        *self.saves.lock().unwrap() += 1;
        Ok(())
    }
}

/// Records, on every `fold` call, the arguments it received so the test can prove
/// incrementality. Deterministic: `up_to = last new turn id`, and
/// `summary_md = prev.summary_md + each new turn's text`.
#[derive(Default)]
struct RecordingSummarizer {
    /// One entry per `fold` call: `(prev_was_some, new_turns_len)`.
    calls: Mutex<Vec<(bool, usize)>>,
}

impl RecordingSummarizer {
    fn calls(&self) -> Vec<(bool, usize)> {
        self.calls.lock().unwrap().clone()
    }
}

#[async_trait]
impl HandoffSummarizer for RecordingSummarizer {
    async fn fold(&self, prev: Option<Handoff>, new_turns: &[ConversationTurn]) -> Handoff {
        self.calls
            .lock()
            .unwrap()
            .push((prev.is_some(), new_turns.len()));

        let mut summary = prev.map(|h| h.summary_md).unwrap_or_default();
        for t in new_turns {
            summary.push_str(&t.text);
        }
        let up_to = new_turns
            .last()
            .map(|t| t.id)
            .expect("fold must receive at least one new turn in these tests");
        Handoff::new(summary, up_to, None)
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[tokio::test]
async fn single_record_appends_turn_and_advances_handoff() {
    let log = Arc::new(InMemoryConversationLog::default());
    let handoffs = Arc::new(InMemoryHandoffStore::default());
    let summarizer = Arc::new(RecordingSummarizer::default());
    let uc = RecordTurn::new(log.clone(), handoffs.clone(), summarizer.clone());

    let conv = conv_id(1);
    let t1 = turn(conv, turn_id(10), "hello world");

    uc.record(conv, t1.clone())
        .await
        .expect("record should succeed");

    // Log contains the turn.
    assert_eq!(log.thread(conv), vec![t1.clone()]);

    // Handoff advanced: up_to == turn id, summary contains the turn text.
    let h = handoffs.loaded(conv).expect("handoff should be saved");
    assert_eq!(h.up_to, t1.id);
    assert!(
        h.summary_md.contains("hello world"),
        "summary={:?}",
        h.summary_md
    );

    // First fold: prev = None, exactly one new turn.
    assert_eq!(summarizer.calls(), vec![(false, 1)]);
    assert_eq!(handoffs.save_count(), 1);
}

#[tokio::test]
async fn two_records_fold_incrementally_without_full_reread() {
    let log = Arc::new(InMemoryConversationLog::default());
    let handoffs = Arc::new(InMemoryHandoffStore::default());
    let summarizer = Arc::new(RecordingSummarizer::default());
    let uc = RecordTurn::new(log.clone(), handoffs.clone(), summarizer.clone());

    let conv = conv_id(1);
    let t1 = turn(conv, turn_id(10), "first-text");
    let t2 = turn(conv, turn_id(20), "second-text");

    uc.record(conv, t1.clone()).await.expect("record t1");
    uc.record(conv, t2.clone()).await.expect("record t2");

    // Log: [t1, t2] in order.
    assert_eq!(log.thread(conv), vec![t1.clone(), t2.clone()]);

    // Handoff up_to == t2.id; summary contains both texts.
    let h = handoffs.loaded(conv).expect("handoff saved");
    assert_eq!(h.up_to, t2.id);
    assert!(
        h.summary_md.contains("first-text"),
        "summary={:?}",
        h.summary_md
    );
    assert!(
        h.summary_md.contains("second-text"),
        "summary={:?}",
        h.summary_md
    );

    // Proof of incrementality: prev None then Some, and len == 1 on BOTH calls
    // (never 2 → the whole log is never re-read into the fold).
    assert_eq!(summarizer.calls(), vec![(false, 1), (true, 1)]);
    assert_eq!(handoffs.save_count(), 2);
}

#[tokio::test]
async fn append_error_propagates_as_store_and_does_not_save() {
    let log = Arc::new(InMemoryConversationLog::failing_append(StoreError::Io(
        "disk full".to_owned(),
    )));
    let handoffs = Arc::new(InMemoryHandoffStore::default());
    let summarizer = Arc::new(RecordingSummarizer::default());
    let uc = RecordTurn::new(log.clone(), handoffs.clone(), summarizer.clone());

    let conv = conv_id(1);
    let err = uc
        .record(conv, turn(conv, turn_id(10), "x"))
        .await
        .expect_err("append failure must surface");

    assert!(matches!(err, AppError::Store(_)), "got {err:?}");

    // No side effect after a failed append: handoff never saved, fold never called.
    assert_eq!(handoffs.save_count(), 0);
    assert!(handoffs.loaded(conv).is_none());
    assert!(summarizer.calls().is_empty());
}

#[tokio::test]
async fn load_error_propagates_as_store() {
    let log = Arc::new(InMemoryConversationLog::default());
    let handoffs = Arc::new(InMemoryHandoffStore::failing_load(StoreError::Io(
        "load boom".to_owned(),
    )));
    let summarizer = Arc::new(RecordingSummarizer::default());
    let uc = RecordTurn::new(log.clone(), handoffs.clone(), summarizer.clone());

    let conv = conv_id(1);
    let err = uc
        .record(conv, turn(conv, turn_id(10), "x"))
        .await
        .expect_err("load failure must surface");

    assert!(matches!(err, AppError::Store(_)), "got {err:?}");
    // Append happened (source of truth first), but no save and no fold.
    assert_eq!(log.thread(conv).len(), 1);
    assert_eq!(handoffs.save_count(), 0);
    assert!(summarizer.calls().is_empty());
}

#[tokio::test]
async fn save_error_propagates_as_store() {
    let log = Arc::new(InMemoryConversationLog::default());
    let handoffs = Arc::new(InMemoryHandoffStore::failing_save(
        StoreError::Serialization("save boom".to_owned()),
    ));
    let summarizer = Arc::new(RecordingSummarizer::default());
    let uc = RecordTurn::new(log.clone(), handoffs.clone(), summarizer.clone());

    let conv = conv_id(1);
    let err = uc
        .record(conv, turn(conv, turn_id(10), "x"))
        .await
        .expect_err("save failure must surface");

    assert!(matches!(err, AppError::Store(_)), "got {err:?}");
    // Append + fold happened, but the save itself failed → nothing stored.
    assert_eq!(log.thread(conv).len(), 1);
    assert_eq!(handoffs.save_count(), 0);
    assert!(handoffs.loaded(conv).is_none());
    assert_eq!(summarizer.calls(), vec![(false, 1)]);
}

#[tokio::test]
async fn records_are_isolated_per_conversation() {
    let log = Arc::new(InMemoryConversationLog::default());
    let handoffs = Arc::new(InMemoryHandoffStore::default());
    let summarizer = Arc::new(RecordingSummarizer::default());
    let uc = RecordTurn::new(log.clone(), handoffs.clone(), summarizer.clone());

    let a = conv_id(1);
    let b = conv_id(2);
    let ta = turn(a, turn_id(10), "alpha");
    let tb = turn(b, turn_id(20), "beta");

    uc.record(a, ta.clone()).await.expect("record a");
    uc.record(b, tb.clone()).await.expect("record b");

    // Logs are kept apart.
    assert_eq!(log.thread(a), vec![ta.clone()]);
    assert_eq!(log.thread(b), vec![tb.clone()]);

    // Handoffs are kept apart: each covers only its own conversation's turn.
    let ha = handoffs.loaded(a).expect("handoff a");
    let hb = handoffs.loaded(b).expect("handoff b");
    assert_eq!(ha.up_to, ta.id);
    assert!(ha.summary_md.contains("alpha") && !ha.summary_md.contains("beta"));
    assert_eq!(hb.up_to, tb.id);
    assert!(hb.summary_md.contains("beta") && !hb.summary_md.contains("alpha"));
}