//! Integration tests for branch-selective ClawSync.
//!
//! These tests exercise the full pipeline:
//!   differ::diff_revisions → selector::filter_packets → merger::merge_packets
//!
//! Scenarios covered:
//! - Sync only a named branch to an empty remote
//! - UpTo selector limits revisions regardless of branch
//! - BranchAt selector combines branch + revision ceiling
//! - Multi-branch source: only target branch lands on remote
//! - Verify page data integrity after branch-selective merge
//! - SyncSelector::All passes everything through (baseline)

use clawhdf5_onion::branch::MergeStrategy;
use clawhdf5_onion::format::NO_PARENT;
use clawhdf5_onion::writer::OnionFile;
use clawsync_onion::differ::diff_revisions;
use clawsync_onion::merger::merge_packets;
use clawsync_onion::selector::{SyncSelector, filter_packets, remote_head_for_selector};
use tempfile::NamedTempFile;

// ─────────────────────────────────────────────────────────────────────────────
// Helpers
// ─────────────────────────────────────────────────────────────────────────────

fn tmp_onion(n_main: u8) -> OnionFile {
    let f = NamedTempFile::new().unwrap();
    let h5 = f.path().with_extension("h5");
    std::fs::write(&h5, b"\x89HDF\r\n\x1a\n").unwrap();
    let mut onion = OnionFile::create(&h5, 4096).unwrap();
    for i in 0..n_main {
        let mut s = onion.begin_session(None).unwrap();
        s.record_page(0, &vec![i; 4096]);
        onion.commit_session(s, Some(&format!("main-{i}"))).unwrap();
    }
    onion
}

fn empty_onion() -> OnionFile {
    let f = NamedTempFile::new().unwrap();
    let h5 = f.path().with_extension("h5");
    std::fs::write(&h5, b"\x89HDF\r\n\x1a\n").unwrap();
    OnionFile::create(&h5, 4096).unwrap()
}

/// Build an onion with `n_main` revisions on main, then fork "feat" and add
/// `n_feat` more revisions on feat.
fn branched_onion(n_main: u8, n_feat: u8) -> OnionFile {
    let mut onion = tmp_onion(n_main);
    onion.create_branch("feat", "main").unwrap();
    let feat_id = onion.branch_by_name("feat").unwrap().id;
    for i in 0..n_feat {
        let mut s = onion.begin_session(Some(feat_id)).unwrap();
        s.record_page(0, &vec![0x80 + i; 4096]);
        onion.commit_session(s, Some(&format!("feat-{i}"))).unwrap();
    }
    onion
}

// ─────────────────────────────────────────────────────────────────────────────
// SyncSelector::All — baseline
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn all_selector_transfers_every_revision() {
    let src = tmp_onion(5);
    let mut dst = empty_onion();

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::All, &src).unwrap();
    let stats = merge_packets(&mut dst, filtered, false).unwrap();

    assert_eq!(stats.revisions_merged, 5);
    assert_eq!(dst.revision_count(), 5);
}

// ─────────────────────────────────────────────────────────────────────────────
// SyncSelector::UpTo
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn up_to_selector_limits_revisions() {
    let src = tmp_onion(6);
    let mut dst = empty_onion();

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::UpTo(3), &src).unwrap();

    // Revisions 0, 1, 2, 3 → 4 packets
    assert_eq!(filtered.len(), 4);
    assert_eq!(filtered.last().unwrap().revision, 3);

    let stats = merge_packets(&mut dst, filtered, false).unwrap();
    assert_eq!(stats.revisions_merged, 4);
    assert_eq!(dst.revision_count(), 4);
}

#[test]
fn up_to_revision_zero_sends_only_first() {
    let src = tmp_onion(4);
    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::UpTo(0), &src).unwrap();
    assert_eq!(filtered.len(), 1);
    assert_eq!(filtered[0].revision, 0);
}

#[test]
fn up_to_beyond_head_sends_all() {
    let src = tmp_onion(3);
    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::UpTo(999), &src).unwrap();
    assert_eq!(filtered.len(), 3);
}

// ─────────────────────────────────────────────────────────────────────────────
// SyncSelector::Branch
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn branch_selector_main_only_sends_main_revisions() {
    // 3 main + 2 feat revisions
    let src = branched_onion(3, 2);
    let mut dst = empty_onion();

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    assert_eq!(packets.len(), 5); // all revisions

    let filtered = filter_packets(packets, &SyncSelector::Branch("main".into()), &src).unwrap();
    assert_eq!(filtered.len(), 3);
    assert!(filtered.iter().all(|p| p.branch_id == 0));

    let stats = merge_packets(&mut dst, filtered, false).unwrap();
    assert_eq!(stats.revisions_merged, 3);
    assert_eq!(dst.revision_count(), 3);
}

#[test]
fn branch_selector_feat_only_sends_feat_revisions() {
    let src = branched_onion(3, 4);
    let feat_id = src.branch_by_name("feat").unwrap().id;

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::Branch("feat".into()), &src).unwrap();

    assert_eq!(filtered.len(), 4);
    assert!(filtered.iter().all(|p| p.branch_id == feat_id));
}

#[test]
fn branch_selector_nonexistent_errors() {
    let src = tmp_onion(2);
    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let result = filter_packets(packets, &SyncSelector::Branch("nope".into()), &src);
    assert!(result.is_err());
}

// ─────────────────────────────────────────────────────────────────────────────
// SyncSelector::BranchAt
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn branch_at_filters_branch_and_revision() {
    // 2 main revisions (0, 1), then 4 feat revisions (2, 3, 4, 5)
    let src = branched_onion(2, 4);
    let feat_id = src.branch_by_name("feat").unwrap().id;

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    // BranchAt("feat", 3) → feat packets with revision ≤ 3 → revisions 2, 3
    let filtered =
        filter_packets(packets, &SyncSelector::BranchAt("feat".into(), 3), &src).unwrap();

    assert_eq!(filtered.len(), 2);
    assert!(filtered.iter().all(|p| p.branch_id == feat_id));
    assert!(filtered.iter().all(|p| p.revision <= 3));
}

#[test]
fn branch_at_main_with_ceiling() {
    let src = tmp_onion(5);

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered =
        filter_packets(packets, &SyncSelector::BranchAt("main".into(), 2), &src).unwrap();

    assert_eq!(filtered.len(), 3); // revisions 0, 1, 2
    assert_eq!(filtered.last().unwrap().revision, 2);
}

#[test]
fn branch_at_nonexistent_branch_errors() {
    let src = tmp_onion(3);
    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let result = filter_packets(packets, &SyncSelector::BranchAt("ghost".into(), 1), &src);
    assert!(result.is_err());
}

// ─────────────────────────────────────────────────────────────────────────────
// Multi-branch source → branch-filtered merge
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn merge_feat_branch_only_to_empty_remote() {
    let src = branched_onion(3, 3);
    let feat_id = src.branch_by_name("feat").unwrap().id;
    let mut dst = empty_onion();

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::Branch("feat".into()), &src).unwrap();

    // Only feat packets → 3 revisions
    assert_eq!(filtered.len(), 3);

    let stats = merge_packets(&mut dst, filtered, false).unwrap();
    assert_eq!(stats.revisions_merged, 3);

    // The remote should have a feat branch with those revisions
    let dst_revs = dst.list_revisions();
    assert_eq!(dst_revs.len(), 3);
    assert!(dst_revs.iter().all(|r| r.branch_id == feat_id));
}

#[test]
fn merge_preserves_page_content_after_branch_filter() {
    let src = branched_onion(2, 2);

    let mut dst = empty_onion();
    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::Branch("main".into()), &src).unwrap();
    merge_packets(&mut dst, filtered, false).unwrap();

    // Main rev 0: page filled with 0x00, rev 1: filled with 0x01
    let rev0_pages = dst.revision_pages(0).unwrap();
    assert!(rev0_pages[0].1.iter().all(|&b| b == 0x00));

    let rev1_pages = dst.revision_pages(1).unwrap();
    assert!(rev1_pages[0].1.iter().all(|&b| b == 0x01));
}

// ─────────────────────────────────────────────────────────────────────────────
// remote_head_for_selector
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn remote_head_empty_remote() {
    assert_eq!(remote_head_for_selector(&SyncSelector::All, 0), NO_PARENT);
}

#[test]
fn remote_head_non_empty_remote() {
    // Remote has 4 revisions (0..=3) → HEAD = 3
    assert_eq!(remote_head_for_selector(&SyncSelector::All, 4), 3);
}

#[test]
fn remote_head_single_revision() {
    assert_eq!(remote_head_for_selector(&SyncSelector::UpTo(5), 1), 0);
}

// ─────────────────────────────────────────────────────────────────────────────
// Incremental sync (diff from non-zero remote_head)
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn incremental_sync_sends_only_new_revisions() {
    let src = tmp_onion(6);

    // Remote already has revisions 0..=2; diff from HEAD=2
    let packets = diff_revisions(&src, 2).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::All, &src).unwrap();

    assert_eq!(filtered.len(), 3); // revisions 3, 4, 5

    let mut dst = tmp_onion(3); // dst already has 0, 1, 2
    let stats = merge_packets(&mut dst, filtered, false).unwrap();
    assert_eq!(stats.revisions_merged, 3);
    assert_eq!(dst.revision_count(), 6);
}

#[test]
fn incremental_branch_sync_sends_only_new_branch_revisions() {
    let src = branched_onion(3, 4); // main: 0,1,2  feat: 3,4,5,6
    let feat_id = src.branch_by_name("feat").unwrap().id;

    // Simulate remote already having feat revisions 3, 4 (remote_head=4)
    let remote_head = remote_head_for_selector(&SyncSelector::Branch("feat".into()), 5);

    let packets = diff_revisions(&src, remote_head).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::Branch("feat".into()), &src).unwrap();

    // Should send feat revisions 5, 6 only
    assert!(filtered.iter().all(|p| p.branch_id == feat_id));
    assert!(filtered.iter().all(|p| p.revision > remote_head));
}

// ─────────────────────────────────────────────────────────────────────────────
// Merge with branched source using ensure_branch_id auto-registration
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn merge_auto_registers_unknown_branch() {
    // Source: 2 main + 2 feat revisions; send ALL to empty remote
    let src = branched_onion(2, 2);
    let mut dst = empty_onion();

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    // All 4 packets — includes both main (branch_id=0) and feat (branch_id=1)
    let stats = merge_packets(&mut dst, packets, false).unwrap();

    assert_eq!(stats.revisions_merged, 4);
    // The remote should have both branches registered
    let branches = dst.list_branches();
    assert!(
        branches.len() >= 2,
        "expected at least 2 branches, got {:?}",
        branches.len()
    );
}

// ─────────────────────────────────────────────────────────────────────────────
// Merge-then-branch on destination (fork from synced state)
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn can_branch_on_remote_after_branch_selective_sync() {
    let src = tmp_onion(3);
    let mut dst = empty_onion();

    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered = filter_packets(packets, &SyncSelector::Branch("main".into()), &src).unwrap();
    merge_packets(&mut dst, filtered, false).unwrap();

    // The remote should now be able to fork its own branch
    let result = dst.create_branch("experiment", "main");
    assert!(
        result.is_ok(),
        "should be able to create branch after sync: {result:?}"
    );
}

// ─────────────────────────────────────────────────────────────────────────────
// Idempotency across selectors
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn branch_filtered_merge_is_idempotent() {
    let src = branched_onion(3, 2);
    let mut dst = empty_onion();

    let packets1 = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered1 = filter_packets(packets1, &SyncSelector::Branch("main".into()), &src).unwrap();
    merge_packets(&mut dst, filtered1, false).unwrap();

    // Apply again — should skip all
    let packets2 = diff_revisions(&src, NO_PARENT).unwrap();
    let filtered2 = filter_packets(packets2, &SyncSelector::Branch("main".into()), &src).unwrap();
    let stats2 = merge_packets(&mut dst, filtered2, false).unwrap();

    assert_eq!(stats2.revisions_merged, 0);
    assert_eq!(stats2.revisions_skipped, 3);
}

// ─────────────────────────────────────────────────────────────────────────────
// merge-then-verify via merge_into (end-to-end with branching)
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn synced_remote_can_merge_branches() {
    let src = branched_onion(3, 2);
    let mut dst = empty_onion();

    // Sync everything
    let packets = diff_revisions(&src, NO_PARENT).unwrap();
    merge_packets(&mut dst, packets, false).unwrap();

    // The feat branch was auto-registered as "branch-{id}" during sync
    let feat_id = src.branch_by_name("feat").unwrap().id;
    let dst_feat_name = format!("branch-{feat_id}");
    let result = dst.merge_into(&dst_feat_name, "main", MergeStrategy::LatestWins);
    assert!(result.is_ok(), "merge_into failed: {result:?}");
    // main should now have an extra revision
    let main_revs: Vec<_> = dst
        .list_revisions()
        .into_iter()
        .filter(|r| r.branch_id == 0)
        .collect();
    assert!(main_revs.len() >= 4); // 3 original + 1 merge commit
}