#!/usr/bin/env python3
"""Template matching, handwriting isolation, and lossless template-text merging."""

from __future__ import annotations

import json
import re
from dataclasses import dataclass
from pathlib import Path
from typing import Any

import cv2
import numpy as np
from PIL import Image


PLACEHOLDER = "{{HANDWRITING}}"
VARIANTS = {
    "adaptive65": {"sigma": 2.5, "floor": 8.0, "percentile": 65.0},
    "adaptive75": {"sigma": 4.0, "floor": 10.0, "percentile": 75.0},
    "adaptive85": {"sigma": 5.5, "floor": 12.0, "percentile": 85.0},
    "fixed20": {"fixed": 20.0},
    "residual2": {"mode": "residual", "floor": 2.0, "gain": 2.0},
    "residual3": {"mode": "residual", "floor": 3.0, "gain": 3.0},
    "residual4": {"mode": "residual", "floor": 4.0, "gain": 4.0},
    "residual6": {"mode": "residual", "floor": 6.0, "gain": 4.0},
    "highpass08": {
        "mode": "highpass",
        "sigma": 0.8,
        "floor": 1.5,
        "gain": 4.0,
    },
    "highpass12": {
        "mode": "highpass",
        "sigma": 1.2,
        "floor": 2.0,
        "gain": 4.0,
    },
    "highpass20": {
        "mode": "highpass",
        "sigma": 2.0,
        "floor": 2.0,
        "gain": 3.0,
    },
    "highpass30": {
        "mode": "highpass",
        "sigma": 3.0,
        "floor": 2.5,
        "gain": 3.0,
    },
}


@dataclass(frozen=True)
class Template:
    id: str
    file: str
    image: np.ndarray
    text_region: tuple[int, int, int, int]
    template_text: str
    blocks: tuple[dict[str, Any], ...]


@dataclass(frozen=True)
class TemplateMatch:
    template: Template
    median_abs_delta: float
    p90_abs_delta: float
    candidate_count: int


def normalize_text(value: str) -> str:
    return " ".join(str(value).split())


def merge_template_text(template_text: str, handwriting: str) -> tuple[str, int]:
    """Insert handwriting once and preserve every Gemini template token."""
    template_text = str(template_text)
    handwriting = normalize_text(handwriting)
    count = template_text.count(PLACEHOLDER)
    if count:
        merged = template_text.replace(PLACEHOLDER, handwriting, 1)
        merged = merged.replace(PLACEHOLDER, "")
    elif normalize_text(template_text):
        merged = f"{template_text} {handwriting}"
    else:
        merged = handwriting
    return normalize_text(merged), count


class TemplateCatalog:
    def __init__(self, background_root: Path, ocr_root: Path):
        background_root = Path(background_root)
        ocr_root = Path(ocr_root)
        manifest = json.loads(
            (background_root / "manifest.json").read_text(encoding="utf-8")
        )
        images: dict[str, np.ndarray] = {}
        templates: list[Template] = []
        for item in manifest:
            filename = str(item["file"])
            if filename not in images:
                with Image.open(background_root / filename) as opened:
                    images[filename] = np.asarray(opened.convert("RGB"))
            result: dict[str, Any] = {}
            ocr_path = ocr_root / f"{item['id']}.json"
            if ocr_path.is_file():
                result = json.loads(
                    ocr_path.read_text(encoding="utf-8")
                ).get("result", {})
            templates.append(
                Template(
                    id=str(item["id"]),
                    file=filename,
                    image=images[filename],
                    text_region=tuple(int(value) for value in item["text_region"]),
                    template_text=str(result.get("template_text", PLACEHOLDER)),
                    blocks=tuple(result.get("blocks", [])),
                )
            )
        self.templates = tuple(templates)
        self.by_id = {template.id: template for template in templates}

    @staticmethod
    def difference(image: np.ndarray, template: np.ndarray) -> np.ndarray:
        if image.shape != template.shape:
            raise ValueError(
                f"image/template shape mismatch: {image.shape} != {template.shape}"
            )
        return np.max(
            np.abs(image.astype(np.int16) - template.astype(np.int16)),
            axis=2,
        ).astype(np.float32)

    def match(self, image: Image.Image | np.ndarray) -> TemplateMatch:
        actual = (
            np.asarray(image.convert("RGB"))
            if isinstance(image, Image.Image)
            else np.asarray(image)
        )
        height, width = actual.shape[:2]
        candidates = [
            template
            for template in self.templates
            if template.image.shape[:2] == (height, width)
        ]
        if not candidates:
            raise ValueError(f"no template has native size {width}x{height}")

        by_file: dict[str, tuple[float, float, np.ndarray]] = {}
        for template in candidates:
            if template.file in by_file:
                continue
            delta = self.difference(actual, template.image)
            by_file[template.file] = (
                float(np.median(delta)),
                float(np.percentile(delta, 90)),
                delta,
            )
        best_file = min(
            by_file,
            key=lambda name: (
                by_file[name][0],
                by_file[name][1],
                name,
            ),
        )
        same_file = [
            template for template in candidates if template.file == best_file
        ]
        median, p90, delta = by_file[best_file]
        if len(same_file) == 1:
            selected = same_file[0]
        else:
            center = float(np.median(delta))
            spread = float(np.median(np.abs(delta - center)))
            threshold = max(8.0, center + 3.0 * max(spread, 1.0))

            def region_energy(template: Template) -> float:
                x0, y0, x1, y1 = template.text_region
                x0 = max(0, min(width, x0))
                x1 = max(0, min(width, x1))
                y0 = max(0, min(height, y0))
                y1 = max(0, min(height, y1))
                region = delta[y0:y1, x0:x1]
                if not region.size:
                    return -1.0
                return float(np.maximum(region - threshold, 0.0).sum()) / region.size

            selected = max(same_file, key=lambda template: (region_energy(template), template.id))
        return TemplateMatch(
            template=selected,
            median_abs_delta=median,
            p90_abs_delta=p90,
            candidate_count=len(candidates),
        )

    @staticmethod
    def _mask(delta: np.ndarray, variant: str) -> tuple[np.ndarray, float]:
        if variant not in VARIANTS:
            raise ValueError(f"unknown isolation variant: {variant}")
        options = VARIANTS[variant]
        if "fixed" in options:
            threshold = float(options["fixed"])
        else:
            center = float(np.median(delta))
            spread = float(np.median(np.abs(delta - center)))
            threshold = max(
                float(options["floor"]),
                center + float(options["sigma"]) * max(spread, 1.0),
                float(np.percentile(delta, float(options["percentile"]))),
            )
        mask = np.uint8(delta >= threshold)
        count, labels, stats, _ = cv2.connectedComponentsWithStats(mask, 8)
        filtered = np.zeros_like(mask)
        for component in range(1, count):
            if int(stats[component, cv2.CC_STAT_AREA]) >= 3:
                filtered[labels == component] = 1
        filtered = cv2.dilate(
            filtered,
            cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (3, 3)),
            iterations=1,
        )
        return filtered.astype(bool), threshold

    @staticmethod
    def _residual(
        actual: np.ndarray,
        template: np.ndarray,
        variant: str,
    ) -> tuple[np.ndarray, dict[str, float]]:
        options = VARIANTS[variant]
        channel_delta = template.astype(np.float32) - actual.astype(np.float32)
        offsets = np.median(channel_delta.reshape(-1, 3), axis=0)
        corrected = channel_delta - offsets.reshape(1, 1, 3)
        signal = np.maximum(corrected.max(axis=2) - float(options["floor"]), 0.0)
        signal = np.clip(signal * float(options["gain"]), 0.0, 245.0)
        raw_mask = np.uint8(signal >= 3.0)
        count, labels, stats, _ = cv2.connectedComponentsWithStats(raw_mask, 8)
        mask = np.zeros_like(raw_mask)
        for component in range(1, count):
            if int(stats[component, cv2.CC_STAT_AREA]) >= 2:
                mask[labels == component] = 1
        darkness = np.zeros_like(signal)
        darkness[mask.astype(bool)] = signal[mask.astype(bool)]
        darkness = cv2.dilate(
            darkness,
            cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (2, 2)),
            iterations=1,
        )
        output = np.full_like(actual, 255)
        value = np.uint8(np.clip(255.0 - darkness, 0.0, 255.0))
        retained = darkness >= 3.0
        output[retained] = np.repeat(value[:, :, None], 3, axis=2)[retained]
        return output, {
            "threshold": float(options["floor"]),
            "gain": float(options["gain"]),
            "kept_fraction": float(retained.mean()),
            "channel_offset_r": float(offsets[0]),
            "channel_offset_g": float(offsets[1]),
            "channel_offset_b": float(offsets[2]),
        }

    @staticmethod
    def _highpass(
        actual: np.ndarray,
        template: np.ndarray,
        variant: str,
    ) -> tuple[np.ndarray, dict[str, float]]:
        options = VARIANTS[variant]
        sigma = float(options["sigma"])
        actual_gray = cv2.cvtColor(actual, cv2.COLOR_RGB2GRAY).astype(np.float32)
        template_gray = cv2.cvtColor(template, cv2.COLOR_RGB2GRAY).astype(np.float32)
        actual_darkness = cv2.GaussianBlur(actual_gray, (0, 0), sigma) - actual_gray
        template_darkness = (
            cv2.GaussianBlur(template_gray, (0, 0), sigma) - template_gray
        )
        signal = np.maximum(
            actual_darkness - template_darkness - float(options["floor"]),
            0.0,
        )
        signal = np.clip(signal * float(options["gain"]), 0.0, 245.0)
        raw_mask = np.uint8(signal >= 3.0)
        count, labels, stats, _ = cv2.connectedComponentsWithStats(raw_mask, 8)
        mask = np.zeros_like(raw_mask)
        for component in range(1, count):
            if int(stats[component, cv2.CC_STAT_AREA]) >= 2:
                mask[labels == component] = 1
        darkness = np.zeros_like(signal)
        darkness[mask.astype(bool)] = signal[mask.astype(bool)]
        darkness = cv2.dilate(
            darkness,
            cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (2, 2)),
            iterations=1,
        )
        retained = darkness >= 3.0
        value = np.uint8(np.clip(255.0 - darkness, 0.0, 255.0))
        output = np.repeat(value[:, :, None], 3, axis=2)
        return output, {
            "threshold": float(options["floor"]),
            "gain": float(options["gain"]),
            "sigma": sigma,
            "kept_fraction": float(retained.mean()),
        }

    @classmethod
    def _render(
        cls,
        actual: np.ndarray,
        template: np.ndarray,
        variant: str,
    ) -> tuple[np.ndarray, dict[str, float]]:
        options = VARIANTS.get(variant)
        if options is None:
            raise ValueError(f"unknown isolation variant: {variant}")
        delta = cls.difference(actual, template)
        if options.get("mode") == "residual":
            output, metrics = cls._residual(actual, template, variant)
        elif options.get("mode") == "highpass":
            output, metrics = cls._highpass(actual, template, variant)
        else:
            mask, threshold = cls._mask(delta, variant)
            output = np.full_like(actual, 255)
            output[mask] = actual[mask]
            metrics = {
                "threshold": threshold,
                "kept_fraction": float(mask.mean()),
            }
        metrics.update(
            {
                "median_abs_delta": float(np.median(delta)),
                "p90_abs_delta": float(np.percentile(delta, 90)),
            }
        )
        return output, metrics

    def isolate_with_template(
        self,
        image: Image.Image | np.ndarray,
        template: Template,
        variant: str,
    ) -> tuple[Image.Image, dict[str, float]]:
        actual = (
            np.asarray(image.convert("RGB"))
            if isinstance(image, Image.Image)
            else np.asarray(image)
        )
        output, metrics = self._render(actual, template.image, variant)
        return Image.fromarray(output, mode="RGB"), metrics

    def isolate(
        self,
        image: Image.Image | np.ndarray,
        variant: str,
    ) -> tuple[Image.Image, TemplateMatch, dict[str, float]]:
        match = self.match(image)
        isolated, metrics = self.isolate_with_template(
            image,
            match.template,
            variant,
        )
        return isolated, match, metrics

    def isolate_crop(
        self,
        image: Image.Image | np.ndarray,
        template_id: str,
        crop_bbox: list[int] | tuple[int, int, int, int],
        variant: str,
    ) -> tuple[Image.Image, dict[str, float]]:
        actual = (
            np.asarray(image.convert("RGB"))
            if isinstance(image, Image.Image)
            else np.asarray(image)
        )
        template = self.by_id[template_id]
        x0, y0, x1, y1 = (int(value) for value in crop_bbox)
        background = template.image[y0:y1, x0:x1]
        if background.shape != actual.shape:
            background = cv2.resize(
                background,
                (actual.shape[1], actual.shape[0]),
                interpolation=cv2.INTER_LANCZOS4,
            )
        output, metrics = self._render(actual, background, variant)
        return Image.fromarray(output, mode="RGB"), metrics


def index_from_id(value: str) -> int:
    match = re.fullmatch(r"handwriting:(\d+)", str(value))
    if not match:
        raise ValueError(f"invalid handwriting row id: {value}")
    return int(match.group(1))