"""Configuration loading with built-in defaults, overridable via config.yaml."""

from __future__ import annotations

from dataclasses import dataclass, field, fields, is_dataclass
from pathlib import Path
from typing import Any

import yaml


@dataclass
class CaptureConfig:
    sample_fps: float = 8.0
    processing_width: int = 960


@dataclass
class AudioConfig:
    sample_rate: int = 16000


@dataclass
class MotionConfig:
    blur_ksize: int = 21
    pixel_threshold: int = 12
    threshold: float = 0.02
    stable_min_duration_s: float = 1.0


@dataclass
class DocumentConfig:
    min_area_ratio: float = 0.04
    # Candidates covering more than this fraction of the frame are rejected
    # as likely background/lighting rather than a document.
    max_area_ratio: float = 0.92
    # Candidates whose long side is more than this many times their short
    # side are rejected (fixes thin sliver/edge-strip false detections).
    max_aspect: float = 6.0
    canny_low: int = 50
    canny_high: int = 150
    # Contour search runs on a frame downscaled to this width; edge/threshold
    # gap-closing kernels are sized relative to it rather than the source
    # resolution, and the winning quad is scaled back up for the actual crop.
    # Verified fix: a 4K frame's document outline was fragmenting into
    # sub-regions with a fixed-pixel kernel tuned for ~1000px-wide frames.
    detect_width: int = 1000
    # Bake illumination-normalization + contrast enhancement into the saved
    # crop/PDF, not just the internal OCR pass (which always applies it).
    enhance: bool = False
    # Auto-detect and correct 0/90/180/270 rotation before OCR/PDF export.
    # Fixes the "placed the document upside down" case, which otherwise
    # produces a fine-looking crop that OCR reads as garbage.
    auto_rotate: bool = True
    # Expand the detected quad outward by this fraction before warping, to
    # recover paper margins clipped by curl/wrinkles (see pad_quad).
    pad_margin: float = 0.04
    # Tighten each crop to the actual paper region (removes mat margins and
    # hands hanging off the side of receipts) and inpaint fingers pressing
    # on the page. Content *under* a finger can't be recovered — it's filled
    # with plausible paper texture — but margins clean up completely.
    refine: bool = True
    remove_fingers: bool = True
    # Frame-based capture: cluster consecutive per-frame detections into
    # separate documents when no contour is seen for this many seconds.
    event_gap_s: float = 2.0
    # Require at least this many sampled frames with a detection before
    # committing a capture event (filters single-frame noise).
    event_min_samples: int = 2


@dataclass
class SpeechConfig:
    window_before_s: float = 3.0
    window_after_s: float = 5.0


@dataclass
class OcrConfig:
    # Tesseract language pack (e.g. "eng", "eng+fra").
    lang: str = "eng"
    # Page segmentation mode. 6 = "assume a single uniform block of text",
    # which (unlike Tesseract's default of 3) keeps each receipt line's
    # item-name and price together instead of splitting them into separate
    # column blocks and dropping one. Verified against synthetic Home Depot/
    # Metro/Petro-Canada receipts; revisit if real receipts have a layout
    # PSM 6 handles worse (e.g. multi-column letters).
    psm: int = 6
    # Vendor name is assumed to live in this top fraction of the crop
    # (receipt headers / letterheads are typically near the top).
    vendor_top_fraction: float = 0.4
    # Words below this Tesseract confidence (0-100) are ignored when
    # picking the vendor line. Kept low deliberately: header text (larger,
    # sometimes bold/stylized fonts) can score much lower confidence than
    # crisp monospace body text despite being read correctly, and the
    # line-height + topmost heuristic already screens out low-confidence
    # noise (garbled OCR hallucinations measure much shorter than real text).
    min_word_confidence: float = 10.0


@dataclass
class LlmConfig:
    # Use a local Ollama vision model to identify/name documents and flag
    # quality issues. Falls back to Tesseract heuristics when Ollama is
    # down or the model errors. minicpm-v is ~8-12s/doc and much less prone
    # to false "blank" labels than qwen2.5vl on dense statement pages.
    enabled: bool = True
    model: str = "minicpm-v"
    base_url: str = "http://localhost:11434"
    timeout_s: float = 180.0


@dataclass
class NamingConfig:
    max_vendor_len: int = 40


@dataclass
class OutputConfig:
    dir: str = "./output"
    consume_dir: str | None = None


@dataclass
class Config:
    capture: CaptureConfig = field(default_factory=CaptureConfig)
    audio: AudioConfig = field(default_factory=AudioConfig)
    motion: MotionConfig = field(default_factory=MotionConfig)
    document: DocumentConfig = field(default_factory=DocumentConfig)
    speech: SpeechConfig = field(default_factory=SpeechConfig)
    ocr: OcrConfig = field(default_factory=OcrConfig)
    llm: LlmConfig = field(default_factory=LlmConfig)
    naming: NamingConfig = field(default_factory=NamingConfig)
    output: OutputConfig = field(default_factory=OutputConfig)


def _merge_into(instance: Any, data: dict[str, Any]) -> Any:
    """Overlay a dict of overrides onto a dataclass instance, recursively."""
    for f in fields(instance):
        if f.name not in data:
            continue
        value = data[f.name]
        current = getattr(instance, f.name)
        if is_dataclass(current) and isinstance(value, dict):
            _merge_into(current, value)
        else:
            setattr(instance, f.name, value)
    return instance


def load_config(path: str | Path | None = None) -> Config:
    """Load config.yaml if present; unknown keys are ignored, missing keys use defaults."""
    cfg = Config()
    if path is None:
        return cfg
    path = Path(path)
    if not path.exists():
        raise FileNotFoundError(f"Config file not found: {path}")
    data = yaml.safe_load(path.read_text()) or {}
    return _merge_into(cfg, data)


def config_to_dict(cfg: Config) -> dict[str, Any]:
    """Serialize the effective config (for embedding in run reports)."""
    from dataclasses import asdict

    return asdict(cfg)