"""Base scraper interface for platform BIOS requirement sources."""

from __future__ import annotations

import json
import sys
import urllib.request
import urllib.error
from abc import ABC, abstractmethod
from dataclasses import dataclass, field


@dataclass
class BiosRequirement:
    """A single BIOS file requirement from a platform source."""
    name: str
    system: str
    sha1: str | None = None
    md5: str | None = None
    crc32: str | None = None
    size: int | None = None
    destination: str = ""
    required: bool = True
    zipped_file: str | None = None  # If set, md5 is for this ROM inside the ZIP


@dataclass
class ChangeSet:
    """Differences between scraped requirements and current config."""
    added: list[BiosRequirement] = field(default_factory=list)
    removed: list[BiosRequirement] = field(default_factory=list)
    modified: list[tuple[BiosRequirement, BiosRequirement]] = field(default_factory=list)

    @property
    def has_changes(self) -> bool:
        return bool(self.added or self.removed or self.modified)

    def summary(self) -> str:
        parts = []
        if self.added:
            parts.append(f"+{len(self.added)} added")
        if self.removed:
            parts.append(f"-{len(self.removed)} removed")
        if self.modified:
            parts.append(f"~{len(self.modified)} modified")
        return ", ".join(parts) if parts else "no changes"


class BaseScraper(ABC):
    """Abstract base class for platform BIOS requirement scrapers."""

    def __init__(self, url: str = ""):
        self.url = url
        self._raw_data: str | None = None

    def _fetch_raw(self) -> str:
        """Fetch raw content from source URL. Cached after first call."""
        if self._raw_data is not None:
            return self._raw_data
        if not self.url:
            raise ValueError("No source URL configured")
        try:
            req = urllib.request.Request(self.url, headers={"User-Agent": "retrobios-scraper/1.0"})
            with urllib.request.urlopen(req, timeout=30) as resp:
                self._raw_data = resp.read().decode("utf-8")
                return self._raw_data
        except urllib.error.URLError as e:
            raise ConnectionError(f"Failed to fetch {self.url}: {e}") from e

    @abstractmethod
    def fetch_requirements(self) -> list[BiosRequirement]:
        """Fetch current BIOS requirements from the platform source."""
        ...

    def compare_with_config(self, config: dict) -> ChangeSet:
        """Compare scraped requirements against existing platform config."""
        scraped = self.fetch_requirements()
        changes = ChangeSet()

        existing = {}
        for sys_id, system in config.get("systems", {}).items():
            for f in system.get("files", []):
                key = (sys_id, f["name"])
                existing[key] = f

        scraped_map = {}
        for req in scraped:
            key = (req.system, req.name)
            scraped_map[key] = req

        for key, req in scraped_map.items():
            if key not in existing:
                changes.added.append(req)
            else:
                existing_file = existing[key]
                if req.sha1 and existing_file.get("sha1") and req.sha1 != existing_file["sha1"]:
                    changes.modified.append((
                        BiosRequirement(
                            name=existing_file["name"],
                            system=key[0],
                            sha1=existing_file.get("sha1"),
                            md5=existing_file.get("md5"),
                        ),
                        req,
                    ))
                elif req.md5 and existing_file.get("md5") and req.md5 != existing_file["md5"]:
                    changes.modified.append((
                        BiosRequirement(
                            name=existing_file["name"],
                            system=key[0],
                            md5=existing_file.get("md5"),
                        ),
                        req,
                    ))

        for key in existing:
            if key not in scraped_map:
                f = existing[key]
                changes.removed.append(BiosRequirement(
                    name=f["name"],
                    system=key[0],
                    sha1=f.get("sha1"),
                    md5=f.get("md5"),
                ))

        return changes

    def test_connection(self) -> bool:
        """Test if the source URL is reachable."""
        try:
            self.fetch_requirements()
            return True
        except (ConnectionError, ValueError, OSError):
            return False

    @abstractmethod
    def validate_format(self, raw_data: str) -> bool:
        """Validate source data format. Returns False if format has changed unexpectedly."""
        ...


def fetch_github_latest_version(repo: str) -> str | None:
    """Fetch the latest release version tag from a GitHub repo."""
    url = f"https://api.github.com/repos/{repo}/releases/latest"
    try:
        req = urllib.request.Request(url, headers={
            "User-Agent": "retrobios-scraper/1.0",
            "Accept": "application/vnd.github.v3+json",
        })
        with urllib.request.urlopen(req, timeout=15) as resp:
            data = json.loads(resp.read())
            return data.get("tag_name", "")
    except (urllib.error.URLError, urllib.error.HTTPError, json.JSONDecodeError):
        return None


def scraper_cli(scraper_class: type, description: str = "Scrape BIOS requirements") -> None:
    """Shared CLI entry point for all scrapers. Eliminates main() boilerplate."""
    import argparse

    parser = argparse.ArgumentParser(description=description)
    parser.add_argument("--dry-run", action="store_true", help="Show scraped data")
    parser.add_argument("--output", "-o", help="Output YAML file")
    parser.add_argument("--json", action="store_true", help="Output as JSON")
    args = parser.parse_args()

    scraper = scraper_class()
    try:
        reqs = scraper.fetch_requirements()
    except (ConnectionError, ValueError) as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)

    if args.dry_run:
        by_system: dict[str, list] = {}
        for req in reqs:
            by_system.setdefault(req.system, []).append(req)
        for system, files in sorted(by_system.items()):
            req_count = sum(1 for f in files if f.required)
            opt_count = len(files) - req_count
            print(f"  {system}: {req_count} required, {opt_count} optional")
        print(f"\nTotal: {len(reqs)} BIOS entries across {len(by_system)} systems")
        return

    if args.json:
        data = [{"name": r.name, "system": r.system, "sha1": r.sha1, "md5": r.md5,
                 "size": r.size, "required": r.required} for r in reqs]
        print(json.dumps(data, indent=2))
        return

    if args.output:
        # Generate platform YAML
        import yaml
        config = {"systems": {}}
        for req in reqs:
            sys_id = req.system
            config["systems"].setdefault(sys_id, {"files": []})
            entry = {"name": req.name, "destination": req.destination or req.name, "required": req.required}
            if req.sha1:
                entry["sha1"] = req.sha1
            if req.md5:
                entry["md5"] = req.md5
            if req.zipped_file:
                entry["zipped_file"] = req.zipped_file
            config["systems"][sys_id]["files"].append(entry)
        with open(args.output, "w") as f:
            yaml.dump(config, f, default_flow_style=False, sort_keys=False)
        print(f"Written {len(reqs)} entries to {args.output}")
        return

    print(f"Scraped {len(reqs)} requirements. Use --dry-run, --json, or --output.")


def fetch_github_latest_tag(repo: str, prefix: str = "") -> str | None:
    """Fetch the most recent matching tag from a GitHub repo."""
    url = f"https://api.github.com/repos/{repo}/tags?per_page=50"
    try:
        req = urllib.request.Request(url, headers={
            "User-Agent": "retrobios-scraper/1.0",
            "Accept": "application/vnd.github.v3+json",
        })
        with urllib.request.urlopen(req, timeout=15) as resp:
            tags = json.loads(resp.read())
            for tag in tags:
                name = tag["name"]
                if prefix and not name.startswith(prefix):
                    continue
                return name
            return tags[0]["name"] if tags else None
    except (urllib.error.URLError, urllib.error.HTTPError, json.JSONDecodeError):
        return None