"""Thumbnail generation as an Activity job (#249 System S5, Task 12).

- ``GET /prompt_manager/images/thumbnails/plan?mode=&size=&quality=`` counts
  what a run would do over every gallery root and writes nothing:
  ``{success, targets, fresh, remaining, roots, mode, size, quality}``.
- ``POST /prompt_manager/jobs/thumbnails {mode, size, quality}`` starts the
  ``thumbnails`` job (202 ``{job}``). Its admission class is ``guarded``: it
  never runs beside a record-changing job, and one thumbnail job runs at a
  time. It stops at a file boundary when cancelled, keeping the previews it
  wrote. Its outcome groups are ``generated``, ``skipped`` (already fresh)
  and ``errors``.

``mode`` is ``missing`` (previews that are absent or older than their file)
or ``rebuild`` (every preview again, fresh ones too). ``size`` is the
preview's longest edge, 128 to 2048 pixels. ``quality`` picks the encoder
settings (``THUMBNAIL_ENCODINGS``). Every preview is written next to the old
one and renamed over it, so nothing is cleared first and a failure keeps the
old preview; originals are only read.

The legacy gallery stream ``POST /images/generate-thumbnails/progress``
starts this job (its quality preset still sizes the previews) or attaches to
the running one. Its first frame, ``job {id, started}``, names that job and
whether this stream started it (the gallery cancels by that id, and only a
job it started); then come the job's legacy ``status``/``start``/
``progress``/``file_error``/``complete`` frames. A client that goes away no
longer stops the work: the job outlives the request, as a scan does.
"""

import asyncio
import functools
import json
import time
from dataclasses import dataclass

from aiohttp import web

from .admin import _plural, _scan_location, _scan_roots, _scan_status_line
from .images import (
    THUMBNAIL_ENCODINGS,
    _BodyTooLarge,
    _new_thumbnail_stats,
    _read_json_body,
    _record_thumbnail_result,
    _thumbnail_batch_size,
    _thumbnail_complete_payload,
    _thumbnail_progress_payload,
    _worker_threads,
)
from .job_routes import busy_response
from .jobs import THUMBNAIL_GROUP_NAMES, THUMBNAILS_JOB_KIND, JobBusy

THUMBNAIL_JOB_TITLE = "Thumbnail generation"
THUMBNAIL_MODES = ("missing", "rebuild")
THUMBNAIL_QUALITIES = tuple(THUMBNAIL_ENCODINGS)
MIN_THUMBNAIL_EDGE = 128
MAX_THUMBNAIL_EDGE = 2048
# The concept's "Preview size limit" default.
DEFAULT_THUMBNAIL_EDGE = 512
DEFAULT_THUMBNAIL_OPTIONS = {
    "mode": "missing",
    "size": DEFAULT_THUMBNAIL_EDGE,
    "quality": "medium",
}
_OPTIONS_ERROR = (
    'mode must be "missing" or "rebuild", quality "low", "medium" or "high", '
    f"and size a whole number of pixels from {MIN_THUMBNAIL_EDGE} "
    f"to {MAX_THUMBNAIL_EDGE}"
)
CANCELLED_ERROR = "Thumbnail generation was cancelled"
CANCELLED_BEFORE_WRITING = "Cancelled before any preview was written"
NOTHING_TO_PREVIEW = "No images or videos to preview"
_MODE_LOG = {"missing": "missing previews", "rebuild": "every preview"}
# Outcome rows: what happened to each file's preview.
_DETAILS = {
    "generated": "Preview written",
    "skipped": "Preview already up to date",
}
_LOG_PREFIXES = {"generated": "+", "errors": "!"}


@dataclass(frozen=True)
class ThumbnailOptions:
    """One run's choices: the mode, the preview's longest edge and quality."""

    mode: str
    edge: int
    quality: str

    @property
    def size(self):
        return (self.edge, self.edge)

    @property
    def encoding(self):
        return THUMBNAIL_ENCODINGS[self.quality]

    @property
    def rebuild(self):
        return self.mode == "rebuild"

    def scope(self):
        return {"mode": self.mode, "size": self.edge, "quality": self.quality}


def _edge(value, *, from_query):
    """The preview edge as an int, or None when it is not one in range."""
    if from_query and isinstance(value, str):
        if not value.isascii() or not value.isdigit() or len(value) > 5:
            return None
        value = int(value)
    if isinstance(value, bool) or not isinstance(value, int):
        return None
    return value if MIN_THUMBNAIL_EDGE <= value <= MAX_THUMBNAIL_EDGE else None


def thumbnail_options(raw, *, from_query=False):
    """``(ThumbnailOptions, None)`` from a body or query, or ``(None, message)``.

    Absent fields take ``DEFAULT_THUMBNAIL_OPTIONS``. Query values are
    strings, so a query ``size`` may be decimal digits; a JSON ``size`` must
    be an int.
    """
    if not isinstance(raw, dict) and not hasattr(raw, "get"):
        return None, _OPTIONS_ERROR
    mode = raw.get("mode", DEFAULT_THUMBNAIL_OPTIONS["mode"])
    quality = raw.get("quality", DEFAULT_THUMBNAIL_OPTIONS["quality"])
    edge = _edge(raw.get("size", DEFAULT_THUMBNAIL_EDGE), from_query=from_query)
    if mode not in THUMBNAIL_MODES or quality not in THUMBNAIL_QUALITIES:
        return None, _OPTIONS_ERROR
    if edge is None:
        return None, _OPTIONS_ERROR
    return ThumbnailOptions(mode, edge, quality), None


def _invalid(message):
    return web.json_response(
        {"success": False, "code": "invalid-request", "error": message}, status=400
    )


def _frame(event, data):
    """A legacy stream frame as the job publishes it."""
    return {"event": event, "data": data}


def _finished_line(plan, stats):
    """A finished job's status line: what it wrote, or that it had nothing to do."""
    if not plan["targets"]:
        if plan["skipped"]:
            return f"No previews to generate · {plan['skipped']:,} already up to date"
        return NOTHING_TO_PREVIEW
    parts = [f"{_plural(stats['generated'], 'preview')} written"]
    if stats["errors"]:
        parts.append(_plural(len(stats["errors"]), "error"))
    if plan["remaining"]:
        parts.append(f"{plan['remaining']:,} more on the next run")
    return " · ".join(parts)


class ThumbnailJobsMixin:
    """The thumbnail plan, the thumbnail job and the legacy stream on it."""

    async def get_thumbnail_plan(self, request):
        """What a thumbnail run would do (read-only; capped like a run)."""
        options, error = thumbnail_options(request.query, from_query=True)
        if error:
            return _invalid(error)
        try:
            output_dirs = await self._run_in_executor(self._get_all_output_dirs)
            plan = await self._run_in_executor(
                self._plan_gallery_thumbnails, output_dirs, rebuild=options.rebuild
            )
        except Exception:
            self.logger.exception("Thumbnail plan failed")
            return web.json_response(
                {
                    "success": False,
                    "code": None,
                    "error": "The thumbnail plan could not be read",
                },
                status=500,
            )
        return web.json_response(
            {
                "success": True,
                "targets": len(plan["targets"]),
                "fresh": plan["fresh"],
                "remaining": plan["remaining"],
                "roots": [self._public_path(root) for root in output_dirs],
                **options.scope(),
            },
            headers={"Cache-Control": "no-store"},
        )

    async def start_thumbnail_job(self, request):
        """Start the thumbnail job (202), or 409 naming the job in the way."""
        body = {}
        if request.can_read_body:
            try:
                body = await _read_json_body(request)
            except _BodyTooLarge:
                return web.json_response(
                    {"success": False, "code": "too-large", "error": "Body too large"},
                    status=413,
                )
            except (ValueError, UnicodeDecodeError):
                return _invalid(_OPTIONS_ERROR)
        options, error = thumbnail_options(body)
        if error:
            return _invalid(error)
        try:
            job = self._start_thumbnail_job(options)
        except JobBusy as busy:
            return busy_response(busy)
        return web.json_response({"success": True, "job": job.summary()}, status=202)

    def _start_thumbnail_job(self, options):
        """Register the thumbnail job synchronously; raises JobBusy."""
        return self._jobs.start(
            THUMBNAILS_JOB_KIND,
            THUMBNAIL_JOB_TITLE,
            admission="guarded",
            cancellable=True,
            scope=options.scope(),
            runner=functools.partial(self._run_thumbnail_job, options=options),
            groups=THUMBNAIL_GROUP_NAMES,
        )

    # ── the job ───────────────────────────────────────────────────────

    async def _run_thumbnail_job(self, job, options):
        try:
            state = await self._thumbnail_job_body(job, options)
        except Exception:
            self.logger.exception("Thumbnail generation failed")
            job.update(status_line="Thumbnail generation stopped on an internal error.")
            job.log_line("Thumbnails failed · internal error")
            job.publish(
                _frame(
                    "error",
                    {
                        "error": "An internal error occurred",
                        "message": "Thumbnail generation failed. Check server logs.",
                    },
                )
            )
            state = "failed"
        job.finish(state)

    async def _thumbnail_job_body(self, job, options):
        """Plan, then generate in worker batches; returns the final state.

        Every exit sets the job's final status line (I3): what was written,
        that there was nothing to do, or what a cancel kept.
        """
        output_dirs = await self._run_in_executor(self._get_all_output_dirs)
        if not output_dirs:
            message = "ComfyUI output directory not found"
            job.update(status_line=message)
            job.log_line(f"Thumbnails failed · {message}")
            job.publish(_frame("error", {"error": message}))
            return "failed"
        folders = _plural(len(output_dirs), "output folder")
        job.scope["output_folders"] = len(output_dirs)
        job.update(status_line=f"Looking for media files in {folders}")
        job.log_line(
            f"Thumbnails started · {folders} · {_MODE_LOG[options.mode]} · "
            f"{options.edge} px · {options.quality}"
        )
        job.publish(
            _frame(
                "status",
                {"phase": "scanning", "message": "Scanning for images and videos..."},
            )
        )
        plan = await self._run_in_executor(
            self._plan_gallery_thumbnails,
            output_dirs,
            rebuild=options.rebuild,
            stop=lambda: job.cancelled,
        )
        if job.cancelled:  # M2: stopped during the walk, before any start frame
            return self._end_cancelled(job, 0, CANCELLED_BEFORE_WRITING)
        roots = _scan_roots(output_dirs)
        self._record_fresh(job, plan, roots)
        stats, start = await self._generate_thumbnail_targets(job, options, plan, roots)
        self.invalidate_gallery_cache()
        generated = _plural(stats["generated"], "preview")
        if job.cancelled:
            return self._end_cancelled(
                job, stats["generated"], f"Cancelled · {generated} written"
            )
        payload = _thumbnail_complete_payload(
            len(plan["targets"]) + plan["skipped"] + plan["remaining"],
            stats,
            start,
            remaining=plan["remaining"],
            processed=len(plan["targets"]),
        )
        job.update(progress=100, status_line=_finished_line(plan, stats))
        if plan["remaining"]:
            job.log_line(
                f"{plan['remaining']:,} more previews are left for the next run"
            )
        errors = _plural(len(stats["errors"]), "error")
        job.log_line(f"Thumbnails finished · {generated} written · {errors}")
        self.logger.info(payload["message"])
        job.publish(_frame("complete", payload))
        return "finished"

    @staticmethod
    def _end_cancelled(job, generated, status_line):
        """Close a cancelled job: its status line, log line and error frame."""
        job.update(status_line=status_line)
        job.log_line(f"Thumbnails cancelled · {_plural(generated, 'preview')} written")
        job.publish(
            _frame("error", {"error": CANCELLED_ERROR, "message": CANCELLED_ERROR})
        )
        return "cancelled"

    def _record_fresh(self, job, plan, roots):
        """List the already fresh previews under Skipped (no log line each)."""
        rows = []
        for src in plan["fresh_files"]:
            path, label, index = _scan_location(src, roots)
            rows.append(
                {
                    "path": path,
                    "root": label,
                    "root_index": index,
                    "detail": _DETAILS["skipped"],
                }
            )
        job.record_counted("skipped", plan["skipped"], rows)
        if plan["skipped"]:
            job.log_line(f"= {plan['skipped']:,} previews already up to date")

    async def _generate_thumbnail_targets(self, job, options, plan, roots):
        """Generate ``plan``'s targets in worker batches, publishing each file."""
        targets = plan["targets"]
        total = len(targets)
        video_count = sum(1 for _, _, is_video in targets if is_video)
        message = (
            f"Found {total - video_count} images and {video_count} videos to process"
        )
        if plan["skipped"]:
            message += f" ({plan['skipped']} already have thumbnails)"
        job.update(total=total)
        if total:  # never "Processing file 0 of 0" (I3)
            job.update(status_line=_scan_status_line(0, total, 0, 0))
        job.publish(
            _frame(
                "start",
                {
                    "total_images": total,
                    "skipped": plan["skipped"],
                    "remaining": plan["remaining"],
                    "phase": "processing",
                    "image_count": total - video_count,
                    "video_count": video_count,
                    "message": message,
                },
            )
        )
        stats = _new_thumbnail_stats()
        stats["skipped"] = plan["skipped"]
        start = time.monotonic()
        batch_size = _thumbnail_batch_size(_worker_threads())
        generate = {
            "encoding": options.encoding,
            "rebuild": options.rebuild,
            "stop": lambda: job.cancelled,
        }
        index = 0
        batches = 0
        for batch_start in range(0, total, batch_size):
            if job.cancelled:
                break
            batch = targets[batch_start : batch_start + batch_size]
            results = await self._run_in_executor(
                self._generate_batch, batch, options.size, **generate
            )
            for (src, _dst, _video), result in zip(batch, results):
                if result["action"] == "cancelled":
                    continue
                index += 1
                _record_thumbnail_result(stats, result)
                self._record_thumbnail_outcome(job, src, result, roots)
                job.update(processed=index, progress=index * 100 // total)
                if result["action"] == "error":
                    job.publish(
                        _frame(
                            "file_error",
                            {"file": result["file"], "error": result["error"]},
                        )
                    )
                job.publish(
                    _frame(
                        "progress",
                        _thumbnail_progress_payload(index, total, stats, result, start),
                    )
                )
            batches += 1
            job.update(
                status_line=_scan_status_line(
                    index, total, batches, time.monotonic() - start
                )
            )
            await asyncio.sleep(0)  # let other requests run between batches
        return stats, start

    @staticmethod
    def _record_thumbnail_outcome(job, src, result, roots):
        path, label, index = _scan_location(src, roots)
        where = f"{label}/{path}" if label else path
        if result["action"] == "error":
            group, detail = "errors", result.get("error") or "failed"
        elif result["action"] == "skipped":
            group, detail = "skipped", _DETAILS["skipped"]
        else:
            group, detail = "generated", _DETAILS["generated"]
        row = {"path": path, "root": label, "root_index": index, "detail": detail}
        if group == "skipped":
            job.record_counted(group, 1, [row])
            return
        job.record(group, row, f"{_LOG_PREFIXES[group]} {where} · {detail}")

    # ── the legacy gallery stream ─────────────────────────────────────

    async def generate_thumbnails_with_progress(self, request):
        """The gallery's thumbnail stream (POST, server-sent events).

        Starts the thumbnail job with the gallery's quality preset as the
        preview size (missing previews, medium encoding, as before), or
        attaches to the running thumbnail job, and streams its frames. A
        legacy hold (the blocking generate or clear) or a record-changing
        job refuses it with the stream's error frame. The job goes on when
        the client goes away.
        """
        thumbnail_size = self._thumbnail_size(request.query.get("quality", "medium"))
        response = web.StreamResponse(
            status=200,
            headers={
                "Content-Type": "text/event-stream",
                "Cache-Control": "no-cache",
                "Connection": "keep-alive",
            },
        )
        await response.prepare(request)
        # M3: read the registry after the last await, so a job that started
        # while the headers went out is attached to, not refused.
        job, started, busy = self._legacy_stream_job(thumbnail_size)
        if busy is not None:
            message = f"{busy.title} already running"
            await self._emit_sse(
                response, "error", {"error": message, "message": message}
            )
            return response
        # No await between the start and the subscription: the lead frame is
        # sent after it, so the stream misses none of the runner's frames.
        events = job.events(lead=_frame("job", {"id": job.id, "started": started}))
        try:
            async for payload in events:
                frame = (
                    f"event: {payload['event']}\ndata: {json.dumps(payload['data'])}"
                )
                await response.write(f"{frame}\n\n".encode("utf-8"))
        except Exception as exc:  # a write failed: the client went away
            self.logger.info(
                f"Thumbnail progress client disconnected ({exc}); "
                "the thumbnails continue in the background"
            )
        finally:
            # Also when aiohttp cancels the handler on disconnect: the job is
            # its own task and goes on.
            await events.aclose()
        return response

    def _legacy_stream_job(self, thumbnail_size):
        """``(job, started, busy)`` for the legacy stream, synchronously.

        Attaches to the running cancellable thumbnail job, or starts one with
        the gallery's preset as the size (missing previews, medium encoding,
        as the gallery always wrote), or names the job in the way.
        """
        running = self._jobs.active(THUMBNAILS_JOB_KIND)
        if running is not None and running.cancellable:
            return running, False, None
        busy = self._jobs.blocker(THUMBNAILS_JOB_KIND, admission="guarded")
        if busy is not None:
            return None, False, busy
        # blocker() said free and nothing awaited since, so the start is admitted.
        options = ThumbnailOptions("missing", thumbnail_size[0], "medium")
        return self._start_thumbnail_job(options), True, None