from __future__ import annotations

import json
from datetime import datetime as _dt
from pathlib import Path
from typing import Optional, Dict, Any

from fastapi import APIRouter, Request, HTTPException, Query
from fastapi import BackgroundTasks
from ..services.orchestrator import _ensure_setup_ready, _run_theme_metadata_enrichment  # type: ignore
from fastapi.responses import JSONResponse, HTMLResponse
from fastapi.templating import Jinja2Templates
from ..services.theme_catalog_loader import (
    load_index,
    project_detail,
    slugify,
    filter_slugs_fast,
    summaries_for_slugs,
)
from ..services.theme_preview import get_theme_preview  # type: ignore
from ..services.theme_catalog_loader import catalog_metrics, prewarm_common_filters  # type: ignore
from ..services.theme_preview import preview_metrics  # type: ignore
from ..services import theme_preview as _theme_preview_mod  # type: ignore  # for error counters
import os
from fastapi import Body

# In-memory client metrics & structured log counters (diagnostics only)
CLIENT_PERF: dict[str, list[float]] = {
    "list_render_ms": [],  # list_ready - list_render_start
    "preview_load_ms": [],  # optional future measure (not yet emitted)
}
LOG_COUNTS: dict[str, int] = {}
MAX_CLIENT_SAMPLES = 500  # cap to avoid unbounded growth

router = APIRouter(prefix="/themes", tags=["themes"])  # /themes/status

# Reuse the main app's template environment so nav globals stay consistent.
try:  # circular-safe import: app defines templates before importing this router
    from ..app import templates as _templates  # type: ignore
except Exception:  # Fallback (tests/minimal contexts)
    _templates = Jinja2Templates(directory=str(Path(__file__).resolve().parent.parent / 'templates'))

THEME_LIST_PATH = Path("config/themes/theme_list.json")
CATALOG_DIR = Path("config/themes/catalog")
STATUS_PATH = Path("csv_files/.setup_status.json")
TAG_FLAG_PATH = Path("csv_files/.tagging_complete.json")


def _iso(ts: float | int | None) -> Optional[str]:
    if ts is None or ts <= 0:
        return None
    try:
        return _dt.fromtimestamp(ts).isoformat(timespec="seconds")
    except Exception:
        return None


def _load_status() -> Dict[str, Any]:
    try:
        if STATUS_PATH.exists():
            return json.loads(STATUS_PATH.read_text(encoding="utf-8") or "{}") or {}
    except Exception:
        pass
    return {}


def _load_fast_theme_list() -> Optional[list[dict[str, Any]]]:
    """Load precomputed lightweight theme list JSON if available.

    Expected structure: {"themes": [{"id": str, "theme": str, "short_description": str, ...}, ...]}
    Returns list or None on failure.
    """
    try:
        if THEME_LIST_PATH.exists():
            raw = json.loads(THEME_LIST_PATH.read_text(encoding="utf-8") or "{}")
            if isinstance(raw, dict):
                arr = raw.get("themes")
                if isinstance(arr, list):
                    # Shallow copy to avoid mutating original reference
                    # NOTE: Regression fix (2025-09-20): theme_list.json produced by current
                    # build pipeline does NOT include an explicit 'id' per theme (only 'theme').
                    # Earlier implementation required e.get('id') causing the fast path to
                    # treat the catalog as empty and show "No themes found." even though
                    # hundreds of themes exist. We now derive the id via slugify(theme) when
                    # missing, and also opportunistically compute a short_description snippet
                    # if absent (trim description to ~110 chars mirroring project_summary logic).
                    out: list[dict[str, Any]] = []
                    for e in arr:
                        if not isinstance(e, dict):
                            continue
                        theme_name = e.get("theme")
                        if not theme_name or not isinstance(theme_name, str):
                            continue
                        _id = e.get("id") or slugify(theme_name)
                        short_desc = e.get("short_description")
                        if not short_desc:
                            desc = e.get("description")
                            if isinstance(desc, str) and desc.strip():
                                sd = desc.strip()
                                if len(sd) > 110:
                                    sd = sd[:107].rstrip() + "…"
                                short_desc = sd
                        out.append({
                            "id": _id,
                            "theme": theme_name,
                            "short_description": short_desc,
                        })
                    # If we ended up with zero items (unexpected) fall back to None so caller
                    # will use full index logic instead of rendering empty state incorrectly.
                    if not out:
                        return None
                    return out
    except Exception:
        return None
    return None


@router.get("/suggest")
@router.get("/api/suggest")
async def theme_suggest(
    request: Request,
    q: str | None = None,
    limit: int | None = Query(10, ge=1, le=50),
):
    """Lightweight theme name suggestions for typeahead.

    Prefers the precomputed fast path (theme_list.json). Falls back to full index if unavailable.
    Returns a compact JSON: {"themes": ["<name>", ...]}.
    """
    try:
        # Optional rate limit using app helper if available
        rl_result = None
        try:
            from ..app import rate_limit_check  # type: ignore
            rl_result = rate_limit_check(request, "suggest")
        except HTTPException as http_ex:  # propagate 429 with headers
            raise http_ex
        except Exception:
            rl_result = None
        lim = int(limit or 10)
        names: list[str] = []
        fast = _load_fast_theme_list()
        if fast is not None:
            try:
                items = fast
                if q:
                    ql = q.lower()
                    items = [e for e in items if isinstance(e.get("theme"), str) and ql in e["theme"].lower()]
                for e in items[: lim * 3]:  # pre-slice before unique
                    nm = e.get("theme")
                    if isinstance(nm, str):
                        names.append(nm)
            except Exception:
                names = []
        if not names:
            # Fallback to full index
            try:
                idx = load_index()
                slugs = filter_slugs_fast(idx, q=q)
                # summaries_for_slugs returns dicts including 'theme'
                infos = summaries_for_slugs(idx, slugs[: lim * 3])
                for inf in infos:
                    nm = inf.get("theme")
                    if isinstance(nm, str):
                        names.append(nm)
            except Exception:
                names = []
        # Deduplicate preserving order, then clamp
        seen: set[str] = set()
        out: list[str] = []
        for nm in names:
            if nm in seen:
                continue
            seen.add(nm)
            out.append(nm)
            if len(out) >= lim:
                break
        resp = JSONResponse({"themes": out})
        if rl_result:
            remaining, reset_epoch = rl_result
            try:
                resp.headers["X-RateLimit-Remaining"] = str(remaining)
                resp.headers["X-RateLimit-Reset"] = str(reset_epoch)
            except Exception:
                pass
        return resp
    except HTTPException as e:
        # Propagate FastAPI HTTPException (e.g., 429 with headers)
        raise e
    except Exception as e:
        return JSONResponse({"themes": [], "error": str(e)}, status_code=500)


def _load_tag_flag_time() -> Optional[float]:
    try:
        if TAG_FLAG_PATH.exists():
            data = json.loads(TAG_FLAG_PATH.read_text(encoding="utf-8") or "{}") or {}
            t = data.get("tagged_at")
            if isinstance(t, str) and t.strip():
                try:
                    return _dt.fromisoformat(t.strip()).timestamp()
                except Exception:
                    return None
    except Exception:
        return None
    return None


@router.get("/status")
async def theme_status():
    """Return current theme export status for the UI.

    Provides counts, mtimes, and freshness vs. tagging flag.
    """
    try:
        status = _load_status()
        theme_list_exists = THEME_LIST_PATH.exists()
        theme_list_mtime_s = THEME_LIST_PATH.stat().st_mtime if theme_list_exists else None
        theme_count: Optional[int] = None
        parse_error: Optional[str] = None
        if theme_list_exists:
            try:
                raw = json.loads(THEME_LIST_PATH.read_text(encoding="utf-8") or "{}") or {}
                if isinstance(raw, dict):
                    themes = raw.get("themes")
                    if isinstance(themes, list):
                        theme_count = len(themes)
            except Exception as e:  # pragma: no cover
                parse_error = f"parse_error: {e}"  # keep short
        yaml_catalog_exists = CATALOG_DIR.exists() and CATALOG_DIR.is_dir()
        yaml_file_count = 0
        if yaml_catalog_exists:
            try:
                yaml_file_count = len([p for p in CATALOG_DIR.iterdir() if p.suffix == ".yml"])  # type: ignore[arg-type]
            except Exception:
                yaml_file_count = -1
        tagged_time = _load_tag_flag_time()
        stale = False
        if tagged_time and theme_list_mtime_s:
            # Stale if tagging flag is newer by > 1 second
            stale = tagged_time > (theme_list_mtime_s + 1)
        # Also stale if we expect a catalog (after any tagging) but have suspiciously few YAMLs (< 100)
        if yaml_catalog_exists and yaml_file_count >= 0 and yaml_file_count < 100:
            stale = True
        last_export_at = status.get("themes_last_export_at") or _iso(theme_list_mtime_s) or None
        resp = {
            "ok": True,
            "theme_list_exists": theme_list_exists,
            "theme_list_mtime": _iso(theme_list_mtime_s),
            "theme_count": theme_count,
            "yaml_catalog_exists": yaml_catalog_exists,
            "yaml_file_count": yaml_file_count,
            "stale": stale,
            "last_export_at": last_export_at,
            "last_export_fast_path": status.get("themes_last_export_fast_path"),
            "phase": status.get("phase"),
            "running": status.get("running"),
        }
        if parse_error:
            resp["parse_error"] = parse_error
        return JSONResponse(resp)
    except Exception as e:  # pragma: no cover
        return JSONResponse({"ok": False, "error": str(e)}, status_code=500)


@router.post("/refresh")
async def theme_refresh(background: BackgroundTasks):
    """Force a theme export refresh without re-tagging if not needed.

    Runs setup readiness with force=False (fast-path export fallback will run). Returns immediately.
    """
    try:
        def _runner():
            try:
                _ensure_setup_ready(lambda _m: None, force=False)
            except Exception:
                pass
            try:
                _run_theme_metadata_enrichment()
            except Exception:
                pass
        background.add_task(_runner)
        return JSONResponse({"ok": True, "started": True})
    except Exception as e:  # pragma: no cover
        return JSONResponse({"ok": False, "error": str(e)}, status_code=500)


# --- Phase E Theme Catalog APIs ---

def _diag_enabled() -> bool:
    return (os.getenv("WEB_THEME_PICKER_DIAGNOSTICS") or "").strip().lower() in {"1", "true", "yes", "on"}


@router.get("/picker", response_class=HTMLResponse)
async def theme_picker_page(request: Request):
    """Render the theme picker shell.

    Dynamic data (list, detail) loads via fragment endpoints. We still inject
    known archetype list for the filter select so it is populated on initial load.
    """
    archetypes: list[str] = []
    try:
        idx = load_index()
        archetypes = sorted({t.deck_archetype for t in idx.catalog.themes if t.deck_archetype})  # type: ignore[arg-type]
    except Exception:
        archetypes = []
    return _templates.TemplateResponse(
        "themes/picker.html",
        {
            "request": request,
            "archetypes": archetypes,
            "theme_picker_diagnostics": _diag_enabled(),
        },
    )

@router.get("/metrics")
async def theme_metrics():
    if not _diag_enabled():
        raise HTTPException(status_code=403, detail="diagnostics_disabled")
    try:
        idx = load_index()
        prewarm_common_filters()
        return JSONResponse({
            "ok": True,
            "etag": idx.etag,
            "catalog": catalog_metrics(),
            "preview": preview_metrics(),
            "client_perf": {
                "list_render_avg_ms": round(sum(CLIENT_PERF["list_render_ms"]) / len(CLIENT_PERF["list_render_ms"])) if CLIENT_PERF["list_render_ms"] else 0,
                "list_render_count": len(CLIENT_PERF["list_render_ms"]),
                "preview_load_avg_ms": round(sum(CLIENT_PERF["preview_load_ms"]) / len(CLIENT_PERF["preview_load_ms"])) if CLIENT_PERF["preview_load_ms"] else 0,
                "preview_load_batch_count": len(CLIENT_PERF["preview_load_ms"]),
            },
            "log_counts": LOG_COUNTS,
        })
    except Exception as e:
        return JSONResponse({"ok": False, "error": str(e)}, status_code=500)


@router.get("/", response_class=HTMLResponse)
async def theme_catalog_simple(request: Request):
    """Simplified catalog: list + search only (no per-row heavy data)."""
    return _templates.TemplateResponse("themes/catalog_simple.html", {"request": request})


@router.get("/{theme_id}", response_class=HTMLResponse)
async def theme_catalog_detail_page(theme_id: str, request: Request):
    """Full detail page for a single theme (standalone route)."""
    try:
        idx = load_index()
    except FileNotFoundError:
        return HTMLResponse("<div class='error'>Catalog unavailable.</div>", status_code=503)
    slug = slugify(theme_id)
    entry = idx.slug_to_entry.get(slug)
    if not entry:
        return HTMLResponse("<div class='error'>Not found.</div>", status_code=404)
    detail = project_detail(slug, entry, idx.slug_to_yaml, uncapped=False)
    # Strip diagnostics-only fields for public page
    detail.pop('has_fallback_description', None)
    detail.pop('editorial_quality', None)
    detail.pop('uncapped_synergies', None)
    # Build example + synergy commanders (reuse logic from preview)
    example_commanders = [c for c in (detail.get("example_commanders") or []) if isinstance(c, str)]
    synergy_commanders_raw = [c for c in (detail.get("synergy_commanders") or []) if isinstance(c, str)]
    seen = set(example_commanders)
    synergy_commanders: list[str] = []
    for c in synergy_commanders_raw:
        if c not in seen:
            synergy_commanders.append(c)
            seen.add(c)
    # Render via reuse of detail fragment inside a page shell
    return _templates.TemplateResponse(
        "themes/detail_page.html",
        {
            "request": request,
            "theme": detail,
            "diagnostics": False,
            "uncapped": False,
            "yaml_available": False,
            "example_commanders": example_commanders,
            "synergy_commanders": synergy_commanders,
            "standalone_page": True,
        },
    )


@router.get("/fragment/list", response_class=HTMLResponse)
async def theme_list_fragment(
    request: Request,
    q: str | None = None,
    archetype: str | None = None,
    bucket: str | None = None,
    colors: str | None = None,
    diagnostics: bool | None = None,
    synergy_mode: str | None = Query(None, description="Synergy display mode: 'capped' (default) or 'full'"),
    limit: int | None = Query(20, ge=1, le=100),
    offset: int | None = Query(0, ge=0),
):
    import time as _t
    t0 = _t.time()
    try:
        idx = load_index()
    except FileNotFoundError:
        return HTMLResponse("<div class='error'>Catalog unavailable.</div>", status_code=503)
    color_list = [c.strip() for c in colors.split(',')] if colors else None
    # Fast filtering (falls back only for legacy logic differences if needed)
    slugs = filter_slugs_fast(idx, q=q, archetype=archetype, bucket=bucket, colors=color_list)
    diag = _diag_enabled() and bool(diagnostics)
    lim = int(limit or 30)
    off = int(offset or 0)
    total = len(slugs)
    slice_slugs = slugs[off: off + lim]
    items = summaries_for_slugs(idx, slice_slugs)
    # Synergy display logic: default 'capped' mode (cap at 6) unless diagnostics & user explicitly requests full
    # synergy_mode can be 'full' to force uncapped in list (still diagnostics-gated to prevent layout spam in prod)
    mode = (synergy_mode or '').strip().lower()
    allow_full = (mode == 'full') and diag  # only diagnostics may request full
    SYNERGY_CAP = 6
    if not allow_full:
        for it in items:
            syns = it.get("synergies") or []
            if isinstance(syns, list) and len(syns) > SYNERGY_CAP:
                it["synergies_capped"] = True
                it["synergies_full"] = syns
                it["synergies"] = syns[:SYNERGY_CAP]
    if not diag:
        for it in items:
            it.pop('has_fallback_description', None)
            it.pop('editorial_quality', None)
    duration_ms = int(((_t.time() - t0) * 1000))
    resp = _templates.TemplateResponse(
        "themes/list_fragment.html",
        {
            "request": request,
            "items": items,
            "diagnostics": diag,
            "total": total,
            "limit": lim,
            "offset": off,
            "next_offset": off + lim if (off + lim) < total else None,
            "prev_offset": off - lim if off - lim >= 0 else None,
        },
    )
    resp.headers["X-ThemeCatalog-Filter-Duration-ms"] = str(duration_ms)
    resp.headers["X-ThemeCatalog-Index-ETag"] = idx.etag
    return resp


@router.get("/fragment/list_simple", response_class=HTMLResponse)
async def theme_list_simple_fragment(
    request: Request,
    q: str | None = None,
    limit: int | None = Query(100, ge=1, le=300),
    offset: int | None = Query(0, ge=0),
):
    """Lightweight list: only id, theme, short_description (for speed).

    Attempts fast path using precomputed theme_list.json; falls back to full index.
    """
    import time as _t
    t0 = _t.time()
    lim = int(limit or 100)
    off = int(offset or 0)
    fast_items = _load_fast_theme_list()
    fast_used = False
    items: list[dict[str, Any]] = []
    total = 0
    if fast_items is not None:
        fast_used = True
        # Filter (substring on theme only) if q provided
        if q:
            ql = q.lower()
            fast_items = [e for e in fast_items if isinstance(e.get("theme"), str) and ql in e["theme"].lower()]
        total = len(fast_items)
        slice_items = fast_items[off: off + lim]
        for e in slice_items:
            items.append({
                "id": e.get("id"),
                "theme": e.get("theme"),
                "short_description": e.get("short_description"),
            })
    else:
        # Fallback: load full index
        try:
            idx = load_index()
        except FileNotFoundError:
            return HTMLResponse("<div class='error'>Catalog unavailable.</div>", status_code=503)
        slugs = filter_slugs_fast(idx, q=q, archetype=None, bucket=None, colors=None)
        total = len(slugs)
        slice_slugs = slugs[off: off + lim]
        items_raw = summaries_for_slugs(idx, slice_slugs)
        for it in items_raw:
            items.append({
                "id": it.get("id"),
                "theme": it.get("theme"),
                "short_description": it.get("short_description"),
            })
    duration_ms = int(((_t.time() - t0) * 1000))
    resp = _templates.TemplateResponse(
        "themes/list_simple_fragment.html",
        {
            "request": request,
            "items": items,
            "total": total,
            "limit": lim,
            "offset": off,
            "next_offset": off + lim if (off + lim) < total else None,
            "prev_offset": off - lim if off - lim >= 0 else None,
        },
    )
    resp.headers['X-ThemeCatalog-Simple-Duration-ms'] = str(duration_ms)
    resp.headers['X-ThemeCatalog-Simple-Fast'] = '1' if fast_used else '0'
    # Consistency: expose same filter duration style header used by full list fragment so
    # tooling / DevTools inspection does not depend on which catalog view is active.
    resp.headers['X-ThemeCatalog-Filter-Duration-ms'] = str(duration_ms)
    return resp


@router.get("/fragment/detail/{theme_id}", response_class=HTMLResponse)
async def theme_detail_fragment(
    theme_id: str,
    diagnostics: bool | None = None,
    uncapped: bool | None = None,
    request: Request = None,
):
    try:
        idx = load_index()
    except FileNotFoundError:
        return HTMLResponse("<div class='error'>Catalog unavailable.</div>", status_code=503)
    slug = slugify(theme_id)
    entry = idx.slug_to_entry.get(slug)
    if not entry:
        return HTMLResponse("<div class='error'>Not found.</div>", status_code=404)
    diag = _diag_enabled() and bool(diagnostics)
    uncapped_enabled = bool(uncapped) and diag
    detail = project_detail(slug, entry, idx.slug_to_yaml, uncapped=uncapped_enabled)
    if not diag:
        detail.pop('has_fallback_description', None)
        detail.pop('editorial_quality', None)
        detail.pop('uncapped_synergies', None)
    return _templates.TemplateResponse(
        "themes/detail_fragment.html",
        {
            "request": request,
            "theme": detail,
            "diagnostics": diag,
            "uncapped": uncapped_enabled,
            "yaml_available": diag,  # gate by diagnostics flag
        },
    )


## (moved metrics route earlier to avoid collision with catch-all /{theme_id})


@router.get("/yaml/{theme_id}")
async def theme_yaml(theme_id: str):
    """Return raw YAML file for a theme (diagnostics/dev only)."""
    if not _diag_enabled():
        raise HTTPException(status_code=403, detail="diagnostics_disabled")
    try:
        idx = load_index()
    except FileNotFoundError:
        raise HTTPException(status_code=503, detail="catalog_unavailable")
    slug = slugify(theme_id)
    # Attempt to locate via slug -> YAML map, fallback path guess
    y = idx.slug_to_yaml.get(slug)
    if not y:
        raise HTTPException(status_code=404, detail="yaml_not_found")
    # Reconstruct minimal YAML (we have dict already)
    import yaml as _yaml  # local import to keep top-level lean
    text = _yaml.safe_dump(y, sort_keys=False)  # type: ignore
    headers = {"Content-Type": "text/plain; charset=utf-8"}
    return HTMLResponse(text, headers=headers)


@router.get("/api/themes")
async def api_themes(
    request: Request,
    q: str | None = Query(None, description="Substring filter on theme or synergies"),
    archetype: str | None = Query(None, description="Filter by deck_archetype"),
    bucket: str | None = Query(None, description="Filter by popularity bucket"),
    colors: str | None = Query(None, description="Comma-separated color initials (e.g. G,W)"),
    limit: int = Query(50, ge=1, le=200),
    offset: int = Query(0, ge=0),
    diagnostics: bool | None = Query(None, description="Force diagnostics mode (allowed only if flag enabled)"),
):
    import time as _t
    t0 = _t.time()
    try:
        idx = load_index()
    except FileNotFoundError:
        raise HTTPException(status_code=503, detail="catalog_unavailable")
    color_list = [c.strip() for c in colors.split(",") if c.strip()] if colors else None
    # Validate archetype quickly (fast path uses underlying entries anyway)
    if archetype:
        present_archetypes = {e.deck_archetype for e in idx.catalog.themes if e.deck_archetype}
        if archetype not in present_archetypes:
            slugs: list[str] = []
        else:
            slugs = filter_slugs_fast(idx, q=q, archetype=archetype, bucket=bucket, colors=color_list)
    else:
        slugs = filter_slugs_fast(idx, q=q, archetype=None, bucket=bucket, colors=color_list)
    total = len(slugs)
    slice_slugs = slugs[offset: offset + limit]
    items = summaries_for_slugs(idx, slice_slugs)
    diag = _diag_enabled() and bool(diagnostics)
    if not diag:
        # Strip diagnostics-only fields
        for it in items:
            # has_fallback_description is diagnostics-only
            it.pop("has_fallback_description", None)
            it.pop("editorial_quality", None)
    duration_ms = int(((_t.time() - t0) * 1000))
    headers = {
        "ETag": idx.etag,
        "Cache-Control": "no-cache",  # Clients may still conditional GET using ETag
        "X-ThemeCatalog-Filter-Duration-ms": str(duration_ms),
    }
    return JSONResponse({
        "ok": True,
        "count": total,
        "items": items,
        "next_offset": offset + limit if (offset + limit) < total else None,
        "stale": False,  # status already exposed elsewhere; keep placeholder for UI
        "generated_at": idx.catalog.metadata_info.generated_at if idx.catalog.metadata_info else None,
        "diagnostics": diag,
    }, headers=headers)


@router.get("/api/search")
async def api_theme_search(
    q: str = Query(..., min_length=1, description="Search query"),
    limit: int = Query(15, ge=1, le=50),
    include_synergies: bool = Query(False, description="Also match synergies (slower)"),
):
    """Lightweight search with tiered matching (exact > prefix > substring).

    Performance safeguards:
    - Stop scanning once we have >= limit and at least one exact/prefix.
    - Substring phase limited to first 250 themes unless still under limit.
    - Optional synergy search (off by default) to avoid wide fan-out of matches like 'aggro' in many synergy lists.
    """
    try:
        idx = load_index()
    except FileNotFoundError:
        return JSONResponse({"ok": False, "error": "catalog_unavailable"}, status_code=503)
    qnorm = q.strip()
    if not qnorm:
        return JSONResponse({"ok": True, "items": []})
    qlower = qnorm.lower()
    exact: list[dict[str, Any]] = []
    prefix: list[dict[str, Any]] = []
    substr: list[dict[str, Any]] = []
    seen: set[str] = set()
    themes_iter = list(idx.catalog.themes)  # type: ignore[attr-defined]
    # Phase 1 + 2: exact / prefix
    for t in themes_iter:
        name = t.theme
        slug = slugify(name)
        lower_name = name.lower()
        if lower_name == qlower or slug == qlower:
            if slug not in seen:
                exact.append({"id": slug, "theme": name})
                seen.add(slug)
            continue
        if lower_name.startswith(qlower):
            if slug not in seen:
                prefix.append({"id": slug, "theme": name})
                seen.add(slug)
        if len(exact) + len(prefix) >= limit:
            break
    # Phase 3: substring (only if still room)
    if (len(exact) + len(prefix)) < limit:
        scan_limit = 250  # cap scan for responsiveness
        for t in themes_iter[:scan_limit]:
            name = t.theme
            slug = slugify(name)
            if slug in seen:
                continue
            if qlower in name.lower():
                substr.append({"id": slug, "theme": name})
                seen.add(slug)
            if (len(exact) + len(prefix) + len(substr)) >= limit:
                break
    ordered = exact + prefix + substr
    # Optional synergy search fill (lowest priority) if still space
    if include_synergies and len(ordered) < limit:
        remaining = limit - len(ordered)
        for t in themes_iter:
            if remaining <= 0:
                break
            slug = slugify(t.theme)
            if slug in seen:
                continue
            syns = getattr(t, 'synergies', None) or []
            try:
                # Only a quick any() scan to keep it cheap
                if any(qlower in s.lower() for s in syns):
                    ordered.append({"id": slug, "theme": t.theme})
                    seen.add(slug)
                    remaining -= 1
            except Exception:
                continue
    if len(ordered) > limit:
        ordered = ordered[:limit]
    return JSONResponse({"ok": True, "items": ordered})


@router.get("/api/theme/{theme_id}")
async def api_theme_detail(
    theme_id: str,
    uncapped: bool | None = Query(False, description="Return uncapped synergy set (diagnostics mode only)"),
    diagnostics: bool | None = Query(None, description="Diagnostics mode gating extra fields"),
):
    try:
        idx = load_index()
    except FileNotFoundError:
        raise HTTPException(status_code=503, detail="catalog_unavailable")
    slug = slugify(theme_id)
    entry = idx.slug_to_entry.get(slug)
    if not entry:
        raise HTTPException(status_code=404, detail="theme_not_found")
    diag = _diag_enabled() and bool(diagnostics)
    detail = project_detail(slug, entry, idx.slug_to_yaml, uncapped=bool(uncapped) and diag)
    if not diag:
        # Remove diagnostics-only fields
        detail.pop("has_fallback_description", None)
        detail.pop("editorial_quality", None)
        detail.pop("uncapped_synergies", None)
    headers = {"ETag": idx.etag, "Cache-Control": "no-cache"}
    return JSONResponse({"ok": True, "theme": detail, "diagnostics": diag}, headers=headers)


@router.get("/api/theme/{theme_id}/preview")
async def api_theme_preview(
    theme_id: str,
    limit: int = Query(12, ge=1, le=30),
    colors: str | None = Query(None, description="Comma separated color filter (currently placeholder)"),
    commander: str | None = Query(None, description="Commander name to bias sampling (future)"),
):
    try:
        payload = get_theme_preview(theme_id, limit=limit, colors=colors, commander=commander)
    except KeyError:
        raise HTTPException(status_code=404, detail="theme_not_found")
    return JSONResponse({"ok": True, "preview": payload})


@router.get("/fragment/preview/{theme_id}", response_class=HTMLResponse)
async def theme_preview_fragment(
    theme_id: str,
    limit: int = Query(12, ge=1, le=30),
    colors: str | None = None,
    commander: str | None = None,
    suppress_curated: bool = Query(False, description="If true, omit curated example cards/commanders from the sample area (used on detail page to avoid duplication)"),
    minimal: bool = Query(False, description="Minimal inline variant (no header/controls/rationale – used in detail page collapsible preview)"),
    request: Request = None,
):
    """Return HTML fragment for theme preview with caching headers.

    Adds ETag and Last-Modified headers (no strong caching – enables conditional GET / 304).
    ETag composed of catalog index etag + stable hash of preview payload (theme id + limit + commander).
    """
    try:
        payload = get_theme_preview(theme_id, limit=limit, colors=colors, commander=commander)
    except KeyError:
        return HTMLResponse("<div class='error'>Theme not found.</div>", status_code=404)
    # Load example commanders (authoritative list) from catalog detail for legality instead of inferring
    example_commanders: list[str] = []
    synergy_commanders: list[str] = []
    try:
        idx = load_index()
        slug = slugify(theme_id)
        entry = idx.slug_to_entry.get(slug)
        if entry:
            detail = project_detail(slug, entry, idx.slug_to_yaml, uncapped=False)
            example_commanders = [c for c in (detail.get("example_commanders") or []) if isinstance(c, str)]
            synergy_commanders_raw = [c for c in (detail.get("synergy_commanders") or []) if isinstance(c, str)]
            # De-duplicate any overlap with example commanders while preserving order
            seen = set(example_commanders)
            for c in synergy_commanders_raw:
                if c not in seen:
                    synergy_commanders.append(c)
                    seen.add(c)
    except Exception:
        example_commanders = []
        synergy_commanders = []
    # Build ETag (use catalog etag + hash of core identifying fields to reflect underlying data drift)
    import hashlib
    import json as _json
    import time as _time
    try:
        idx = load_index()
        catalog_tag = idx.etag
    except Exception:
        catalog_tag = "unknown"
    hash_src = _json.dumps({
        "theme": theme_id,
        "limit": limit,
        "commander": commander,
        "sample": payload.get("sample", [])[:3],  # small slice for stability & speed
        "v": 1,
    }, sort_keys=True).encode("utf-8")
    etag = "pv-" + hashlib.sha256(hash_src).hexdigest()[:20] + f"-{catalog_tag}"
    # Conditional request support
    if request is not None:
        inm = request.headers.get("if-none-match")
        if inm and inm == etag:
            # 304 Not Modified – FastAPI HTMLResponse with empty body & headers
            resp = HTMLResponse(status_code=304, content="")
            resp.headers["ETag"] = etag
            from email.utils import formatdate as _fmtdate
            resp.headers["Last-Modified"] = _fmtdate(timeval=_time.time(), usegmt=True)
            resp.headers["Cache-Control"] = "no-cache"
            return resp
    ctx = {
        "request": request,
        "preview": payload,
        "example_commanders": example_commanders,
        "synergy_commanders": synergy_commanders,
        "theme_id": theme_id,
        "etag": etag,
        "suppress_curated": suppress_curated,
        "minimal": minimal,
    }
    resp = _templates.TemplateResponse("themes/preview_fragment.html", ctx)
    resp.headers["ETag"] = etag
    from email.utils import formatdate as _fmtdate
    resp.headers["Last-Modified"] = _fmtdate(timeval=_time.time(), usegmt=True)
    resp.headers["Cache-Control"] = "no-cache"
    return resp


# --- Preview Export Endpoints (CSV / JSON) ---
@router.get("/preview/{theme_id}/export.json")
async def export_preview_json(
    theme_id: str,
    limit: int = Query(12, ge=1, le=60),
    colors: str | None = None,
    commander: str | None = None,
    curated_only: bool | None = Query(False, description="If true, only curated example + curated synergy entries returned"),
):
    try:
        payload = get_theme_preview(theme_id, limit=limit, colors=colors, commander=commander)
    except KeyError:
        raise HTTPException(status_code=404, detail="theme_not_found")
    items = payload.get("sample", [])
    if curated_only:
        items = [i for i in items if any(r in {"example", "curated_synergy", "synthetic"} for r in (i.get("roles") or []))]
    return JSONResponse({
        "ok": True,
        "theme": payload.get("theme"),
        "theme_id": payload.get("theme_id"),
        "curated_only": bool(curated_only),
        "generated_at": payload.get("generated_at"),
        "limit": limit,
        "count": len(items),
        "items": items,
    })


@router.get("/preview/{theme_id}/export.csv")
async def export_preview_csv(
    theme_id: str,
    limit: int = Query(12, ge=1, le=60),
    colors: str | None = None,
    commander: str | None = None,
    curated_only: bool | None = Query(False, description="If true, only curated example + curated synergy entries returned"),
):
    import csv as _csv
    import io as _io
    try:
        payload = get_theme_preview(theme_id, limit=limit, colors=colors, commander=commander)
    except KeyError:
        raise HTTPException(status_code=404, detail="theme_not_found")
    rows = payload.get("sample", [])
    if curated_only:
        rows = [r for r in rows if any(role in {"example", "curated_synergy", "synthetic"} for role in (r.get("roles") or []))]
    buf = _io.StringIO()
    fieldnames = ["name", "roles", "score", "rarity", "mana_cost", "color_identity_list", "pip_colors", "reasons", "tags"]
    w = _csv.DictWriter(buf, fieldnames=fieldnames)
    w.writeheader()
    for r in rows:
        w.writerow({
            "name": r.get("name"),
            "roles": ";".join(r.get("roles") or []),
            "score": r.get("score"),
            "rarity": r.get("rarity"),
            "mana_cost": r.get("mana_cost"),
            "color_identity_list": ";".join(r.get("color_identity_list") or []),
            "pip_colors": ";".join(r.get("pip_colors") or []),
            "reasons": ";".join(r.get("reasons") or []),
            "tags": ";".join(r.get("tags") or []),
        })
    csv_text = buf.getvalue()
    from fastapi.responses import Response
    filename = f"preview_{theme_id}.csv"
    headers = {
        "Content-Disposition": f"attachment; filename={filename}",
        "Content-Type": "text/csv; charset=utf-8",
    }
    return Response(content=csv_text, media_type="text/csv", headers=headers)


# --- Export preview as deck seed (lightweight) ---
@router.get("/preview/{theme_id}/export_seed.json")
async def export_preview_seed(
    theme_id: str,
    limit: int = Query(12, ge=1, le=60),
    colors: str | None = None,
    commander: str | None = None,
    curated_only: bool | None = Query(False, description="If true, only curated example + curated synergy entries influence seed list"),
):
    """Return a minimal structure usable to bootstrap a deck build flow.

    Output:
      theme_id, theme, commander (if any), cards (list of names), curated (subset), generated_at.
    """
    try:
        payload = get_theme_preview(theme_id, limit=limit, colors=colors, commander=commander)
    except KeyError:
        raise HTTPException(status_code=404, detail="theme_not_found")
    items = payload.get("sample", [])
    def _is_curated(it: dict) -> bool:
        roles = it.get("roles") or []
        return any(r in {"example","curated_synergy"} for r in roles)
    if curated_only:
        items = [i for i in items if _is_curated(i)]
    card_names = [i.get("name") for i in items if i.get("name") and not i.get("name").startswith("[")]
    curated_names = [i.get("name") for i in items if _is_curated(i) and i.get("name")]  # exclude synthetic placeholders
    return JSONResponse({
        "ok": True,
        "theme": payload.get("theme"),
        "theme_id": payload.get("theme_id"),
        "commander": commander,
        "limit": limit,
        "curated_only": bool(curated_only),
        "generated_at": payload.get("generated_at"),
        "count": len(card_names),
        "cards": card_names,
        "curated": curated_names,
    })


# --- New: Client performance marks ingestion (Section E) ---
@router.post("/metrics/client")
async def ingest_client_metrics(request: Request, payload: dict[str, Any] = Body(...)):
    if not _diag_enabled():
        raise HTTPException(status_code=403, detail="diagnostics_disabled")
    try:
        events = payload.get("events")
        if not isinstance(events, list):
            return JSONResponse({"ok": False, "error": "invalid_events"}, status_code=400)
        for ev in events:
            if not isinstance(ev, dict):
                continue
            name = ev.get("name")
            dur = ev.get("duration_ms")
            if name == "list_render" and isinstance(dur, (int, float)) and dur >= 0:
                CLIENT_PERF["list_render_ms"].append(float(dur))
                if len(CLIENT_PERF["list_render_ms"]) > MAX_CLIENT_SAMPLES:
                    # Drop oldest half to keep memory bounded
                    CLIENT_PERF["list_render_ms"] = CLIENT_PERF["list_render_ms"][len(CLIENT_PERF["list_render_ms"])//2:]
            elif name == "preview_load_batch":
                # Aggregate average into samples list (store avg redundantly for now)
                avg_ms = ev.get("avg_ms")
                if isinstance(avg_ms, (int, float)) and avg_ms >= 0:
                    CLIENT_PERF["preview_load_ms"].append(float(avg_ms))
                    if len(CLIENT_PERF["preview_load_ms"]) > MAX_CLIENT_SAMPLES:
                        CLIENT_PERF["preview_load_ms"] = CLIENT_PERF["preview_load_ms"][len(CLIENT_PERF["preview_load_ms"])//2:]
        return JSONResponse({"ok": True, "ingested": len(events)})
    except Exception as e:  # pragma: no cover
        return JSONResponse({"ok": False, "error": str(e)}, status_code=500)


# --- New: Structured logging ingestion for cache/prefetch events (Section E) ---
@router.post("/log")
async def ingest_structured_log(request: Request, payload: dict[str, Any] = Body(...)):
    if not _diag_enabled():
        raise HTTPException(status_code=403, detail="diagnostics_disabled")
    try:
        event = payload.get("event")
        if not isinstance(event, str) or not event:
            return JSONResponse({"ok": False, "error": "missing_event"}, status_code=400)
        LOG_COUNTS[event] = LOG_COUNTS.get(event, 0) + 1
        if event == "preview_fetch_error":  # client-side fetch failure
            try:
                _theme_preview_mod._PREVIEW_REQUEST_ERROR_COUNT += 1  # type: ignore[attr-defined]
            except Exception:
                pass
        # Lightweight echo back
        return JSONResponse({"ok": True, "count": LOG_COUNTS[event]})
    except Exception as e:  # pragma: no cover
        return JSONResponse({"ok": False, "error": str(e)}, status_code=500)