"""Bundle export — the only channel to noteman (ADR 0001).

    song.zip
      song.json
      original.pdf
      001.webp 002.webp …

Array order in `song.json` *is* slice order: one ordering, not two. Markers
nest inside the slice they sit on, so an index appears in exactly one place —
a jump source's `destination`.
"""

from __future__ import annotations

import json
import re
import zipfile
from pathlib import Path

from .pdf import Source
from .project import Project
from .render import render_song

FORMAT_VERSION = 1
METADATA_FIELDS = (
    "title",
    "subtitle",
    "composer",
    "original_artist",
    "arranger",
    "lyricist",
    "translator",
    "tempo",
    "voices",
)

# Beats per minute, exported as a JSON number. A figure is worth more than a
# word here: "Andante" cannot drive a metronome and two people will not agree
# what it means.
NUMERIC_FIELDS = frozenset({"tempo"})


def filename(project: Project) -> str:
    """The bundle's name, from the song's title.

    Spaces become dashes and anything that is not a letter, digit, dash, dot or
    underscore goes. Letters keep their accents — ä and ö are not a filesystem's
    problem — but a leading dot would make the bundle invisible.
    """
    # Drop the unsafe characters before collapsing whitespace, not after, or
    # "Sävel & Ääni" keeps the dash the ampersand left behind.
    title = re.sub(r"[^\w\s.-]", "", (project.metadata.get("title") or ""))
    return f"{re.sub(r'\s+', '-', title.strip()).lstrip('.-') or 'song'}.zip"


def _engraving(project: Project, page: int, slot: int) -> dict | None:
    """The notation behind a re-engraved slice, or None for a scanned one.

    The slice image stays the presentation; this is the notation it was made
    from, carried so the music can be edited again or turned into sound. Key
    and time are resolved against the song defaults here — a consumer reading
    one slice should not have to know what the rest of the song inherited.
    """
    replacement = project.pages[page].replacements[slot]
    if not replacement or not replacement.voices:
        return None
    return {
        "lang": "lilypond",
        "key": replacement.key or project.key,
        "time": replacement.time or project.time,
        "print_time": replacement.print_time,
        **({"bar": replacement.bar} if replacement.bar else {}),
        "voices": [
            {"clef": v.clef, "notes": v.notes.strip()}
            | ({"lyrics": v.lyrics.strip()} if v.lyrics.strip() else {})
            for v in replacement.voices
        ],
    }


def song_json(project: Project, files: list[str]) -> dict:
    payload: dict = {"v": FORMAT_VERSION}
    for field in METADATA_FIELDS:
        value = (project.metadata.get(field) or "").strip()
        if not value:
            continue
        if field in NUMERIC_FIELDS:
            try:
                payload[field] = int(value)
            except ValueError:
                continue  # not a number, so not worth exporting as one
        else:
            payload[field] = value

    kept = project.kept_slices()
    # Markers reference slices by (page, slot) while editing, because that is
    # what survives adding and removing cuts. In the bundle they become the
    # array index, which is the only cross-reference the format has.
    index_of = {position: i for i, position in enumerate(kept)}

    slices: list[dict] = []
    for name, (page, slot) in zip(files, kept):
        entry: dict = {"file": name}
        engraving = _engraving(project, page, slot)
        if engraving:
            entry["engraving"] = engraving
        markers = []
        for marker in project.pages[page].markers[slot]:
            item: dict = {"type": marker.type}
            if marker.label:
                item["label"] = marker.label
            if marker.destination is not None:
                target = index_of.get(tuple(marker.destination))
                # A jump whose target was discarded or re-cut away is dropped
                # rather than exported dangling: noteman would have nothing to
                # resolve it to.
                if target is None:
                    continue
                item["destination"] = target
            markers.append(item)
        if markers:
            entry["markers"] = markers
        slices.append(entry)

    payload["slices"] = slices
    return payload


def write(project: Project, source: Source, path: Path) -> Path:
    """Render the song and write the bundle. Returns the zip path.

    A title is required; every other metadata field is optional. noteman's own
    rule is that a song needs a title and at least one slice, and a bundle that
    cannot become a song is not worth writing.
    """
    if not project.metadata.get("title", "").strip():
        raise ValueError("a title is required before a song can be exported")

    images = render_song(project, source)
    if not images:
        raise ValueError("no slices to export — every slice is discarded")
    names = [f"{i + 1:03}.webp" for i in range(len(images))]

    path = Path(path)
    path.parent.mkdir(parents=True, exist_ok=True)
    # ZIP_STORED for the images: WebP is already compressed, so deflating it
    # only costs time. The JSON is small enough not to care.
    with zipfile.ZipFile(path, "w") as zf:
        zf.writestr(
            "song.json",
            json.dumps(song_json(project, names), indent=2, ensure_ascii=False),
            zipfile.ZIP_DEFLATED,
        )
        if project.source.exists():
            pdf = project.source.read_bytes()
            if project.optimise_pdf:
                import pymupdf

                from .pdfopt import optimise

                shrunk, _ = optimise(pymupdf.open(project.source), len(pdf))
                pdf = shrunk or pdf  # empty means it found no saving
            zf.writestr("original.pdf", pdf, zipfile.ZIP_STORED)
        for name, data in zip(names, images):
            zf.writestr(name, data, zipfile.ZIP_STORED)

    # The project is spent once its song has been exported: the next edit
    # session starts fresh from detection rather than resuming these decisions.
    # Recorded here so no caller can forget it.
    project.exported = True
    project.save()
    return path