"""
Dependency management module for artifact dependencies.

Handles:
- Parsing orchard.ensure files
- Storing dependencies in the database
- Querying dependencies and reverse dependencies
- Dependency resolution with topological sorting
- Circular dependency detection
- Conflict detection
"""

import re
import yaml
from typing import List, Dict, Any, Optional, Set, Tuple
from sqlalchemy.orm import Session
from sqlalchemy import and_

# Import packaging for PEP 440 version matching
try:
    from packaging.specifiers import SpecifierSet, InvalidSpecifier
    from packaging.version import Version, InvalidVersion
    HAS_PACKAGING = True
except ImportError:
    HAS_PACKAGING = False

from .models import (
    Project,
    Package,
    Artifact,
    Tag,
    ArtifactDependency,
    PackageVersion,
)
from .schemas import (
    EnsureFileContent,
    EnsureFileDependency,
    DependencyResponse,
    ArtifactDependenciesResponse,
    DependentInfo,
    ReverseDependenciesResponse,
    ResolvedArtifact,
    DependencyResolutionResponse,
    DependencyConflict,
    PaginationMeta,
)


class DependencyError(Exception):
    """Base exception for dependency errors."""
    pass


class CircularDependencyError(DependencyError):
    """Raised when a circular dependency is detected."""
    def __init__(self, cycle: List[str]):
        self.cycle = cycle
        super().__init__(f"Circular dependency detected: {' -> '.join(cycle)}")


class DependencyConflictError(DependencyError):
    """Raised when conflicting dependency versions are detected."""
    def __init__(self, conflicts: List[DependencyConflict]):
        self.conflicts = conflicts
        super().__init__(f"Dependency conflicts detected: {len(conflicts)} conflict(s)")


class DependencyNotFoundError(DependencyError):
    """Raised when a dependency cannot be resolved."""
    def __init__(self, project: str, package: str, constraint: str):
        self.project = project
        self.package = package
        self.constraint = constraint
        super().__init__(f"Dependency not found: {project}/{package}@{constraint}")


class InvalidEnsureFileError(DependencyError):
    """Raised when the ensure file is invalid."""
    pass


class DependencyDepthExceededError(DependencyError):
    """Raised when dependency resolution exceeds max depth."""
    def __init__(self, max_depth: int):
        self.max_depth = max_depth
        super().__init__(f"Dependency resolution exceeded maximum depth of {max_depth}")


# Safety limits to prevent DoS attacks
MAX_DEPENDENCY_DEPTH = 50  # Maximum levels of nested dependencies
MAX_DEPENDENCIES_PER_ARTIFACT = 200  # Maximum direct dependencies per artifact


def parse_ensure_file(content: bytes) -> EnsureFileContent:
    """
    Parse an orchard.ensure file.

    Args:
        content: Raw bytes of the ensure file

    Returns:
        Parsed EnsureFileContent

    Raises:
        InvalidEnsureFileError: If the file is invalid YAML or has wrong structure
    """
    try:
        data = yaml.safe_load(content.decode('utf-8'))
    except yaml.YAMLError as e:
        raise InvalidEnsureFileError(f"Invalid YAML: {e}")
    except UnicodeDecodeError as e:
        raise InvalidEnsureFileError(f"Invalid encoding: {e}")

    if data is None:
        return EnsureFileContent(dependencies=[])

    if not isinstance(data, dict):
        raise InvalidEnsureFileError("Ensure file must be a YAML dictionary")

    dependencies = []
    deps_data = data.get('dependencies', [])

    if not isinstance(deps_data, list):
        raise InvalidEnsureFileError("'dependencies' must be a list")

    # Safety limit: prevent DoS through excessive dependencies
    if len(deps_data) > MAX_DEPENDENCIES_PER_ARTIFACT:
        raise InvalidEnsureFileError(
            f"Too many dependencies: {len(deps_data)} exceeds maximum of {MAX_DEPENDENCIES_PER_ARTIFACT}"
        )

    for i, dep in enumerate(deps_data):
        if not isinstance(dep, dict):
            raise InvalidEnsureFileError(f"Dependency {i} must be a dictionary")

        project = dep.get('project')
        package = dep.get('package')
        version = dep.get('version')
        tag = dep.get('tag')

        if not project:
            raise InvalidEnsureFileError(f"Dependency {i} missing 'project'")
        if not package:
            raise InvalidEnsureFileError(f"Dependency {i} missing 'package'")
        if not version and not tag:
            raise InvalidEnsureFileError(
                f"Dependency {i} must have either 'version' or 'tag'"
            )
        if version and tag:
            raise InvalidEnsureFileError(
                f"Dependency {i} cannot have both 'version' and 'tag'"
            )

        dependencies.append(EnsureFileDependency(
            project=project,
            package=package,
            version=version,
            tag=tag,
        ))

    return EnsureFileContent(dependencies=dependencies)


def validate_dependencies(
    db: Session,
    dependencies: List[EnsureFileDependency],
) -> List[str]:
    """
    Validate that all dependency projects exist.

    Args:
        db: Database session
        dependencies: List of dependencies to validate

    Returns:
        List of error messages (empty if all valid)
    """
    errors = []

    for dep in dependencies:
        project = db.query(Project).filter(Project.name == dep.project).first()
        if not project:
            errors.append(f"Project '{dep.project}' not found")

    return errors


def store_dependencies(
    db: Session,
    artifact_id: str,
    dependencies: List[EnsureFileDependency],
) -> List[ArtifactDependency]:
    """
    Store dependencies for an artifact.

    Args:
        db: Database session
        artifact_id: The artifact ID that has these dependencies
        dependencies: List of dependencies to store

    Returns:
        List of created ArtifactDependency objects
    """
    created = []

    for dep in dependencies:
        artifact_dep = ArtifactDependency(
            artifact_id=artifact_id,
            dependency_project=dep.project,
            dependency_package=dep.package,
            version_constraint=dep.version,
            tag_constraint=dep.tag,
        )
        db.add(artifact_dep)
        created.append(artifact_dep)

    return created


def get_artifact_dependencies(
    db: Session,
    artifact_id: str,
) -> List[DependencyResponse]:
    """
    Get all dependencies for an artifact.

    Args:
        db: Database session
        artifact_id: The artifact ID

    Returns:
        List of DependencyResponse objects
    """
    deps = db.query(ArtifactDependency).filter(
        ArtifactDependency.artifact_id == artifact_id
    ).all()

    return [DependencyResponse.from_orm_model(dep) for dep in deps]


def get_reverse_dependencies(
    db: Session,
    project_name: str,
    package_name: str,
    page: int = 1,
    limit: int = 50,
) -> ReverseDependenciesResponse:
    """
    Get all artifacts that depend on a given package.

    Args:
        db: Database session
        project_name: Target project name
        package_name: Target package name
        page: Page number (1-indexed)
        limit: Results per page

    Returns:
        ReverseDependenciesResponse with dependents and pagination
    """
    # Query dependencies that point to this project/package
    query = db.query(ArtifactDependency).filter(
        ArtifactDependency.dependency_project == project_name,
        ArtifactDependency.dependency_package == package_name,
    )

    total = query.count()
    offset = (page - 1) * limit
    deps = query.offset(offset).limit(limit).all()

    dependents = []
    for dep in deps:
        # Get artifact info to find the project/package/version
        artifact = db.query(Artifact).filter(Artifact.id == dep.artifact_id).first()
        if not artifact:
            continue

        # Find which package this artifact belongs to via tags or versions
        tag = db.query(Tag).filter(Tag.artifact_id == dep.artifact_id).first()
        if tag:
            pkg = db.query(Package).filter(Package.id == tag.package_id).first()
            if pkg:
                proj = db.query(Project).filter(Project.id == pkg.project_id).first()
                if proj:
                    # Get version if available
                    version_record = db.query(PackageVersion).filter(
                        PackageVersion.artifact_id == dep.artifact_id,
                        PackageVersion.package_id == pkg.id,
                    ).first()

                    dependents.append(DependentInfo(
                        artifact_id=dep.artifact_id,
                        project=proj.name,
                        package=pkg.name,
                        version=version_record.version if version_record else None,
                        constraint_type="version" if dep.version_constraint else "tag",
                        constraint_value=dep.version_constraint or dep.tag_constraint,
                    ))

    total_pages = (total + limit - 1) // limit

    return ReverseDependenciesResponse(
        project=project_name,
        package=package_name,
        dependents=dependents,
        pagination=PaginationMeta(
            page=page,
            limit=limit,
            total=total,
            total_pages=total_pages,
            has_more=page < total_pages,
        ),
    )


def _is_version_constraint(version_str: str) -> bool:
    """Check if a version string contains constraint operators."""
    if not version_str:
        return False
    # Check for common constraint operators
    return any(op in version_str for op in ['>=', '<=', '!=', '~=', '>', '<', '==', '*'])


def _resolve_version_constraint(
    db: Session,
    package: Package,
    constraint: str,
) -> Optional[Tuple[str, str, int]]:
    """
    Resolve a version constraint (e.g., '>=1.9') to a specific version.

    Uses PEP 440 version matching to find the best matching version.

    Args:
        db: Database session
        package: Package to search versions in
        constraint: Version constraint string (e.g., '>=1.9', '<2.0,>=1.5')

    Returns:
        Tuple of (artifact_id, resolved_version, size) or None if not found
    """
    if not HAS_PACKAGING:
        # Fallback: if packaging not available, can't do constraint matching
        return None

    # Handle wildcard - return latest version
    if constraint == '*':
        # Get the latest version by created_at
        latest = db.query(PackageVersion).filter(
            PackageVersion.package_id == package.id,
        ).order_by(PackageVersion.created_at.desc()).first()
        if latest:
            artifact = db.query(Artifact).filter(Artifact.id == latest.artifact_id).first()
            if artifact:
                return (artifact.id, latest.version, artifact.size)
        return None

    try:
        specifier = SpecifierSet(constraint)
    except InvalidSpecifier:
        # Invalid constraint (e.g., ">=" without version) - treat as wildcard
        # This can happen with malformed metadata from PyPI packages
        latest = db.query(PackageVersion).filter(
            PackageVersion.package_id == package.id,
        ).order_by(PackageVersion.created_at.desc()).first()
        if latest:
            artifact = db.query(Artifact).filter(Artifact.id == latest.artifact_id).first()
            if artifact:
                return (artifact.id, latest.version, artifact.size)
        return None

    # Get all versions for this package
    all_versions = db.query(PackageVersion).filter(
        PackageVersion.package_id == package.id,
    ).all()

    if not all_versions:
        return None

    # Find matching versions
    matching = []
    for pv in all_versions:
        try:
            v = Version(pv.version)
            if v in specifier:
                matching.append((pv, v))
        except InvalidVersion:
            # Skip invalid versions
            continue

    if not matching:
        return None

    # Sort by version (descending) and return the latest matching
    matching.sort(key=lambda x: x[1], reverse=True)
    best_match = matching[0][0]

    artifact = db.query(Artifact).filter(Artifact.id == best_match.artifact_id).first()
    if artifact:
        return (artifact.id, best_match.version, artifact.size)

    return None


def _resolve_dependency_to_artifact(
    db: Session,
    project_name: str,
    package_name: str,
    version: Optional[str],
    tag: Optional[str],
) -> Optional[Tuple[str, str, int]]:
    """
    Resolve a dependency constraint to an artifact ID.

    Supports:
    - Exact version matching (e.g., '1.2.3')
    - Version constraints (e.g., '>=1.9', '<2.0,>=1.5')
    - Tag matching
    - Wildcard ('*' for any version)

    Args:
        db: Database session
        project_name: Project name
        package_name: Package name
        version: Version or version constraint
        tag: Tag constraint

    Returns:
        Tuple of (artifact_id, resolved_version_or_tag, size) or None if not found
    """
    # Get project and package
    project = db.query(Project).filter(Project.name == project_name).first()
    if not project:
        return None

    package = db.query(Package).filter(
        Package.project_id == project.id,
        Package.name == package_name,
    ).first()
    if not package:
        return None

    if version:
        # Check if this is a version constraint (>=, <, etc.) or exact version
        if _is_version_constraint(version):
            result = _resolve_version_constraint(db, package, version)
            if result:
                return result
        else:
            # Look up by exact version
            pkg_version = db.query(PackageVersion).filter(
                PackageVersion.package_id == package.id,
                PackageVersion.version == version,
            ).first()
            if pkg_version:
                artifact = db.query(Artifact).filter(
                    Artifact.id == pkg_version.artifact_id
                ).first()
                if artifact:
                    return (artifact.id, version, artifact.size)

        # Also check if there's a tag with this exact name
        tag_record = db.query(Tag).filter(
            Tag.package_id == package.id,
            Tag.name == version,
        ).first()
        if tag_record:
            artifact = db.query(Artifact).filter(
                Artifact.id == tag_record.artifact_id
            ).first()
            if artifact:
                return (artifact.id, version, artifact.size)

    if tag:
        # Look up by tag
        tag_record = db.query(Tag).filter(
            Tag.package_id == package.id,
            Tag.name == tag,
        ).first()
        if tag_record:
            artifact = db.query(Artifact).filter(
                Artifact.id == tag_record.artifact_id
            ).first()
            if artifact:
                return (artifact.id, tag, artifact.size)

    return None


def _detect_package_cycle(
    db: Session,
    project_name: str,
    package_name: str,
    target_project: str,
    target_package: str,
    visiting: Set[str],
    visited: Set[str],
    path: List[str],
) -> Optional[List[str]]:
    """
    Detect cycles at the package level using DFS.

    Args:
        db: Database session
        project_name: Current project being visited
        package_name: Current package being visited
        target_project: The project we're checking for cycles back to
        target_package: The package we're checking for cycles back to
        visiting: Set of package keys currently in the recursion stack
        visited: Set of fully processed package keys
        path: Current path for cycle reporting

    Returns:
        Cycle path if detected, None otherwise
    """
    pkg_key = f"{project_name}/{package_name}"

    # Check if we've reached the target package (cycle detected)
    if project_name == target_project and package_name == target_package:
        return path + [pkg_key]

    if pkg_key in visiting:
        # Unexpected internal cycle
        return None

    if pkg_key in visited:
        return None

    visiting.add(pkg_key)
    path.append(pkg_key)

    # Get the package and find any artifacts with dependencies
    project = db.query(Project).filter(Project.name == project_name).first()
    if project:
        package = db.query(Package).filter(
            Package.project_id == project.id,
            Package.name == package_name,
        ).first()
        if package:
            # Find all artifacts in this package via tags
            tags = db.query(Tag).filter(Tag.package_id == package.id).all()
            artifact_ids = {t.artifact_id for t in tags}

            # Get dependencies from all artifacts in this package
            for artifact_id in artifact_ids:
                deps = db.query(ArtifactDependency).filter(
                    ArtifactDependency.artifact_id == artifact_id
                ).all()

                for dep in deps:
                    cycle = _detect_package_cycle(
                        db,
                        dep.dependency_project,
                        dep.dependency_package,
                        target_project,
                        target_package,
                        visiting,
                        visited,
                        path,
                    )
                    if cycle:
                        return cycle

    path.pop()
    visiting.remove(pkg_key)
    visited.add(pkg_key)

    return None


def check_circular_dependencies(
    db: Session,
    artifact_id: str,
    new_dependencies: List[EnsureFileDependency],
    project_name: Optional[str] = None,
    package_name: Optional[str] = None,
) -> Optional[List[str]]:
    """
    Check if adding the new dependencies would create a circular dependency.

    Args:
        db: Database session
        artifact_id: The artifact that will have these dependencies
        new_dependencies: Dependencies to be added
        project_name: Project name (optional, will try to look up from tag if not provided)
        package_name: Package name (optional, will try to look up from tag if not provided)

    Returns:
        Cycle path if detected, None otherwise
    """
    # First, get the package info for this artifact to build path labels
    if project_name and package_name:
        current_path = f"{project_name}/{package_name}"
    else:
        # Try to look up from tag
        artifact = db.query(Artifact).filter(Artifact.id == artifact_id).first()
        if not artifact:
            return None

        # Find package for this artifact
        tag = db.query(Tag).filter(Tag.artifact_id == artifact_id).first()
        if not tag:
            return None

        package = db.query(Package).filter(Package.id == tag.package_id).first()
        if not package:
            return None

        project = db.query(Project).filter(Project.id == package.project_id).first()
        if not project:
            return None

        current_path = f"{project.name}/{package.name}"

    # Extract target project and package from current_path
    if "/" in current_path:
        target_project, target_package = current_path.split("/", 1)
    else:
        return None

    # For each new dependency, check if it would create a cycle back to our package
    for dep in new_dependencies:
        # Check if this dependency (transitively) depends on us at the package level
        visiting: Set[str] = set()
        visited: Set[str] = set()
        path: List[str] = [current_path]

        # Check from the dependency's package
        cycle = _detect_package_cycle(
            db,
            dep.project,
            dep.package,
            target_project,
            target_package,
            visiting,
            visited,
            path,
        )
        if cycle:
            return cycle

    return None


def resolve_dependencies(
    db: Session,
    project_name: str,
    package_name: str,
    ref: str,
    base_url: str,
) -> DependencyResolutionResponse:
    """
    Resolve all dependencies for an artifact recursively.

    Args:
        db: Database session
        project_name: Project name
        package_name: Package name
        ref: Tag or version reference
        base_url: Base URL for download URLs

    Returns:
        DependencyResolutionResponse with all resolved artifacts

    Raises:
        DependencyNotFoundError: If a dependency cannot be resolved
        CircularDependencyError: If circular dependencies are detected
        DependencyConflictError: If conflicting versions are required
    """
    # Resolve the initial artifact
    project = db.query(Project).filter(Project.name == project_name).first()
    if not project:
        raise DependencyNotFoundError(project_name, package_name, ref)

    package = db.query(Package).filter(
        Package.project_id == project.id,
        Package.name == package_name,
    ).first()
    if not package:
        raise DependencyNotFoundError(project_name, package_name, ref)

    # Try to find artifact by tag or version
    resolved = _resolve_dependency_to_artifact(
        db, project_name, package_name, ref, ref
    )
    if not resolved:
        raise DependencyNotFoundError(project_name, package_name, ref)

    root_artifact_id, root_version, root_size = resolved

    # Track resolved artifacts and their versions
    resolved_artifacts: Dict[str, ResolvedArtifact] = {}
    # Track version requirements for conflict detection
    version_requirements: Dict[str, List[Dict[str, Any]]] = {}  # pkg_key -> [(version, required_by)]
    # Track visiting/visited for cycle detection
    visiting: Set[str] = set()
    visited: Set[str] = set()
    # Resolution order (topological)
    resolution_order: List[str] = []

    def _resolve_recursive(
        artifact_id: str,
        proj_name: str,
        pkg_name: str,
        version_or_tag: str,
        size: int,
        required_by: Optional[str],
        depth: int = 0,
    ):
        """Recursively resolve dependencies with cycle/conflict detection."""
        # Safety limit: prevent DoS through deeply nested dependencies
        if depth > MAX_DEPENDENCY_DEPTH:
            raise DependencyDepthExceededError(MAX_DEPENDENCY_DEPTH)

        pkg_key = f"{proj_name}/{pkg_name}"

        # Cycle detection (at artifact level)
        if artifact_id in visiting:
            # Build cycle path
            raise CircularDependencyError([pkg_key, pkg_key])

        # Conflict detection - check if we've seen this package before with a different version
        if pkg_key in version_requirements:
            existing_versions = {r["version"] for r in version_requirements[pkg_key]}
            if version_or_tag not in existing_versions:
                # Conflict detected - same package, different version
                requirements = version_requirements[pkg_key] + [
                    {"version": version_or_tag, "required_by": required_by}
                ]
                raise DependencyConflictError([
                    DependencyConflict(
                        project=proj_name,
                        package=pkg_name,
                        requirements=[
                            {
                                "version": r["version"],
                                "required_by": [{"path": r["required_by"]}] if r["required_by"] else []
                            }
                            for r in requirements
                        ],
                    )
                ])
            # Same version already resolved - skip
            if artifact_id in visited:
                return

        if artifact_id in visited:
            return

        visiting.add(artifact_id)

        # Track version requirement
        if pkg_key not in version_requirements:
            version_requirements[pkg_key] = []
        version_requirements[pkg_key].append({
            "version": version_or_tag,
            "required_by": required_by,
        })

        # Get dependencies
        deps = db.query(ArtifactDependency).filter(
            ArtifactDependency.artifact_id == artifact_id
        ).all()

        # Resolve each dependency first (depth-first)
        for dep in deps:
            resolved_dep = _resolve_dependency_to_artifact(
                db,
                dep.dependency_project,
                dep.dependency_package,
                dep.version_constraint,
                dep.tag_constraint,
            )

            if not resolved_dep:
                constraint = dep.version_constraint or dep.tag_constraint
                raise DependencyNotFoundError(
                    dep.dependency_project,
                    dep.dependency_package,
                    constraint,
                )

            dep_artifact_id, dep_version, dep_size = resolved_dep
            _resolve_recursive(
                dep_artifact_id,
                dep.dependency_project,
                dep.dependency_package,
                dep_version,
                dep_size,
                pkg_key,
                depth + 1,
            )

        visiting.remove(artifact_id)
        visited.add(artifact_id)

        # Add to resolution order (dependencies before dependents)
        resolution_order.append(artifact_id)

        # Store resolved artifact info
        resolved_artifacts[artifact_id] = ResolvedArtifact(
            artifact_id=artifact_id,
            project=proj_name,
            package=pkg_name,
            version=version_or_tag,
            size=size,
            download_url=f"{base_url}/api/v1/project/{proj_name}/{pkg_name}/+/{version_or_tag}",
        )

    # Start resolution from root
    _resolve_recursive(
        root_artifact_id,
        project_name,
        package_name,
        root_version,
        root_size,
        None,
    )

    # Build response in topological order
    resolved_list = [resolved_artifacts[aid] for aid in resolution_order]
    total_size = sum(r.size for r in resolved_list)

    return DependencyResolutionResponse(
        requested={
            "project": project_name,
            "package": package_name,
            "ref": ref,
        },
        resolved=resolved_list,
        total_size=total_size,
        artifact_count=len(resolved_list),
    )