// view.cpp — REAPER-facing Design View shell (Phase D2). See view.h.
//
// Compiled into the reaper_reasampler MODULE. Includes reaper_plugin_functions.h
// WITHOUT REAPERAPI_IMPLEMENT — main.cpp is the one TU that defines the API
// pointers; here they are extern (CLAUDE.md §contract).
//
// The tree arithmetic (I_FOLDERDEPTH -> FolderTree) lives in the pure view_tree
// module so it is unit-tested outside the DAW; this file owns only the REAPER
// reads/writes and the snapshot-before-park ordering.

#include "view.h"

#include <set>
#include <string>
#include <vector>

#include "track_guid.h"
#include "view_tree.h"

#define REAPERAPI_MINIMAL
#define REAPERAPI_WANT_CountTracks
#define REAPERAPI_WANT_GetTrack
#define REAPERAPI_WANT_GetMediaTrackInfo_Value
#define REAPERAPI_WANT_SetMediaTrackInfo_Value
#define REAPERAPI_WANT_TrackFX_GetCount
#define REAPERAPI_WANT_TrackFX_GetOffline
#define REAPERAPI_WANT_TrackFX_SetOffline
#define REAPERAPI_WANT_Undo_BeginBlock2
#define REAPERAPI_WANT_Undo_EndBlock2
#include "reaper_plugin_functions.h"

namespace reasampler {

namespace {

// The parmname for each planner Flag. All four are documented bool*/int* track
// info params driven through the double-valued Get/SetMediaTrackInfo_Value API.
const char* flagParm(Flag f) {
    switch (f) {
        case Flag::ShowInTcp:   return "B_SHOWINTCP";
        case Flag::ShowInMixer: return "B_SHOWINMIXER";
        case Flag::MainSend:    return "B_MAINSEND";
        case Flag::FxEnable:    return "I_FXEN";
    }
    return "B_SHOWINTCP";  // unreachable; keeps the compiler quiet
}

// Reads the arrange-ordered track list and their I_FOLDERDEPTH, keyed by GUID.
// The master track is NOT enumerated by GetTrack (index space is the non-master
// tracks), so it can never enter the tree — the master-untouched invariant holds
// by construction. Also caches the MediaTrack* per GUID so later apply steps
// resolve a GUID back to its handle without a second linear scan.
std::vector<TrackFolderEntry> readFolderEntries(
        ReaProject* proj,
        std::vector<std::pair<std::string, MediaTrack*>>& handleByGuid) {
    std::vector<TrackFolderEntry> entries;
    int count = CountTracks(proj);
    entries.reserve(static_cast<std::size_t>(count));
    handleByGuid.reserve(static_cast<std::size_t>(count));
    for (int i = 0; i < count; ++i) {
        MediaTrack* tr = GetTrack(proj, i);
        if (!tr) continue;
        std::string guid = guidString(tr);
        if (guid.empty()) continue;
        int depth = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FOLDERDEPTH"));
        entries.push_back(TrackFolderEntry{guid, depth});
        handleByGuid.emplace_back(guid, tr);
    }
    return entries;
}

MediaTrack* resolve(const std::vector<std::pair<std::string, MediaTrack*>>& handleByGuid,
                    const std::string& guid) {
    for (const auto& kv : handleByGuid) {
        if (kv.first == guid) return kv.second;
    }
    return nullptr;  // stale/deleted GUID — pruned by being skipped
}

// Captures a track's prior driven-flag state BEFORE it is parked. Reads only the
// four owned flags + per-FX offline; never B_MUTE/I_SOLO, never the master (not
// reachable here). ints preserve whatever REAPER reported (defensive per D1's
// TrackSnapshot contract).
TrackSnapshot snapshotTrack(MediaTrack* tr) {
    TrackSnapshot snap;
    snap.showInTcp   = static_cast<int>(GetMediaTrackInfo_Value(tr, "B_SHOWINTCP"));
    snap.showInMixer = static_cast<int>(GetMediaTrackInfo_Value(tr, "B_SHOWINMIXER"));
    snap.mainSend    = static_cast<int>(GetMediaTrackInfo_Value(tr, "B_MAINSEND"));
    snap.fxEnable    = static_cast<int>(GetMediaTrackInfo_Value(tr, "I_FXEN"));

    int fxCount = TrackFX_GetCount(tr);
    snap.fxOffline.reserve(static_cast<std::size_t>(fxCount));
    for (int fx = 0; fx < fxCount; ++fx) {
        snap.fxOffline.push_back(TrackFX_GetOffline(tr, fx) ? 1 : 0);
    }
    return snap;
}

// Applies the planner's scalar-flag writes. B_* are bool* params, I_FXEN is int*,
// all driven through the double API — marshal the plan's int value to double.
void applyFlags(MediaTrack* tr, const std::vector<TrackFlagOp>& flags) {
    for (const TrackFlagOp& op : flags) {
        SetMediaTrackInfo_Value(tr, flagParm(op.flag), static_cast<double>(op.value));
    }
}

// Parks a track's FX offline: the pure park plan leaves fxOffline empty by design;
// the shell expands it from the live FX count and offlines every slot.
void parkFxOffline(MediaTrack* tr) {
    int fxCount = TrackFX_GetCount(tr);
    for (int fx = 0; fx < fxCount; ++fx) {
        TrackFX_SetOffline(tr, fx, true);
    }
}

// Restores per-FX offline from the snapshot verbatim — each slot back to its
// captured value, never a blanket "online". Bounds-checked against the live FX
// count in case the plugin chain changed while parked (prune-safe).
//
// HAZARD (deferred, PLAN "reconcile on delete/restructure"): the remap is by
// slot INDEX, not plugin identity. If the FX chain changed while the track was
// parked, snapshot slot k is restored onto whatever plugin now occupies slot k —
// the bounds-check guards against out-of-range, not against a reshuffled chain.
// Acceptable for D2; full identity-based reconciliation is future hardening.
void restoreFxOffline(MediaTrack* tr, const std::vector<FxOfflineOp>& fxOffline) {
    int fxCount = TrackFX_GetCount(tr);
    for (const FxOfflineOp& op : fxOffline) {
        if (op.fxIndex < 0 || op.fxIndex >= fxCount) continue;
        TrackFX_SetOffline(tr, op.fxIndex, op.offline);
    }
}

} // namespace

bool applyMode(ViewModeModel& model, const std::string& targetModeId, ReaProject* proj) {
    // Reject an unregistered target before touching the project (no partial apply).
    if (!model.modes().contains(targetModeId)) {
        return false;
    }

    std::vector<std::pair<std::string, MediaTrack*>> handleByGuid;
    std::vector<TrackFolderEntry> entries = readFolderEntries(proj, handleByGuid);
    FolderTree tree = buildFolderTree(entries);

    TogglePlan plan = model.planToggle(tree, targetModeId);

    Undo_BeginBlock2(proj);

    // PARK: snapshot BEFORE mutating, store into the model (so restore survives a
    // save-while-parked), then apply the park writes + expand the FX-offline loop.
    for (const TrackPlan& tp : plan.park) {
        // Every op in a TrackPlan targets the same track; take the guid from the
        // first flag op (the pure park plan always emits the four flag ops).
        if (tp.flags.empty()) continue;
        const std::string& guid = tp.flags.front().guid;
        MediaTrack* tr = resolve(handleByGuid, guid);
        if (!tr) continue;  // stale GUID — prune

        model.storeSnapshot(guid, snapshotTrack(tr));
        applyFlags(tr, tp.flags);
        parkFxOffline(tr);
    }

    // RESTORE: apply the snapshot-sourced flag + per-FX offline writes verbatim,
    // then drop the now-consumed snapshot so a re-park recaptures fresh state.
    for (const TrackPlan& tp : plan.restore) {
        if (tp.flags.empty()) continue;
        const std::string& guid = tp.flags.front().guid;
        MediaTrack* tr = resolve(handleByGuid, guid);
        if (!tr) continue;  // stale GUID — prune

        applyFlags(tr, tp.flags);
        restoreFxOffline(tr, tp.fxOffline);
        model.clearSnapshot(guid);
    }

    // PARENT VISIBILITY (derived, never parked): a folder is visible iff at least
    // one of its descendant leaves is visible in the target mode. That derivation is
    // pure (membership + active mode), so it is recomputed every toggle rather than
    // snapshotted — the four leaf-park flags don't apply to parents. Drive only the
    // two visibility flags; never touch B_MAINSEND/I_FXEN/FX-offline on a parent.
    std::set<std::string> visible = model.visibleTracks(tree, targetModeId);
    for (const FolderNode& node : tree.nodes) {
        if (!node.isParent) continue;
        MediaTrack* tr = resolve(handleByGuid, node.guid);
        if (!tr) continue;  // stale GUID — prune
        double show = visible.count(node.guid) ? 1.0 : 0.0;
        SetMediaTrackInfo_Value(tr, "B_SHOWINTCP", show);
        SetMediaTrackInfo_Value(tr, "B_SHOWINMIXER", show);
    }

    model.setActiveMode(targetModeId);

    Undo_EndBlock2(proj, "ReaSampler: apply Design View mode", -1);
    return true;
}

} // namespace reasampler