import os
from flask import Flask, jsonify, request
from werkzeug.exceptions import RequestEntityTooLarge

from .extensions import db, login_manager
from .models import AppSettings, User
from .cli import init_db_command


def create_app():
    app = Flask(__name__, instance_relative_config=True)

    # Basic config
    # Flask ships with SECRET_KEY=None by default, so setdefault() won't override it.
    app.config["SECRET_KEY"] = os.environ.get("SECRET_KEY") or "dev-secret-change-me"
    app.config.setdefault(
        "SQLALCHEMY_DATABASE_URI",
        os.environ.get("DATABASE_URL", "sqlite:///" + os.path.join(app.instance_path, "signage.sqlite")),
    )
    app.config.setdefault("SQLALCHEMY_TRACK_MODIFICATIONS", False)
    app.config.setdefault("UPLOAD_FOLDER", os.path.join(app.root_path, "static", "uploads"))

    # NOTE: Videos should be max 250MB.
    # Flask's MAX_CONTENT_LENGTH applies to the full request payload (multipart includes overhead).
    # We set this slightly above 250MB to allow for multipart/form fields overhead, while still
    # blocking excessively large uploads early.
    app.config.setdefault("MAX_CONTENT_LENGTH", 260 * 1024 * 1024)  # ~260MB request cap

    # Explicit per-video validation lives in the upload route; this app-wide cap is a safety net.

    os.makedirs(app.instance_path, exist_ok=True)
    os.makedirs(app.config["UPLOAD_FOLDER"], exist_ok=True)

    # Init extensions
    db.init_app(app)
    login_manager.init_app(app)
    login_manager.login_view = "auth.login"

    # Lightweight migration(s) for SQLite DBs created before new columns existed.
    # This avoids requiring Alembic for this small project.
    with app.app_context():
        try:
            uri = app.config.get("SQLALCHEMY_DATABASE_URI", "") or ""
            if uri.startswith("sqlite:"):
                cols = [r[1] for r in db.session.execute(db.text("PRAGMA table_info(user)")).fetchall()]
                if "email" not in cols:
                    db.session.execute(db.text("ALTER TABLE user ADD COLUMN email VARCHAR(255)"))
                    # Best-effort unique index (SQLite doesn't support adding unique constraints after the fact).
                    db.session.execute(db.text("CREATE UNIQUE INDEX IF NOT EXISTS ix_user_email ON user (email)"))
                    db.session.commit()

                # Displays: ensure optional description column exists.
                display_cols = [
                    r[1] for r in db.session.execute(db.text("PRAGMA table_info(display)")).fetchall()
                ]
                if "description" not in display_cols:
                    db.session.execute(db.text("ALTER TABLE display ADD COLUMN description VARCHAR(200)"))
                    db.session.commit()

                # Companies: optional per-company storage quota
                company_cols = [
                    r[1] for r in db.session.execute(db.text("PRAGMA table_info(company)")).fetchall()
                ]
                if "storage_max_bytes" not in company_cols:
                    db.session.execute(db.text("ALTER TABLE company ADD COLUMN storage_max_bytes BIGINT"))
                    db.session.commit()

                # AppSettings: create settings table if missing.
                # (PRAGMA returns empty if the table doesn't exist.)
                settings_cols = [
                    r[1] for r in db.session.execute(db.text("PRAGMA table_info(app_settings)")).fetchall()
                ]
                if not settings_cols:
                    AppSettings.__table__.create(db.engine, checkfirst=True)

                # AppSettings: add public_domain column if missing.
                if settings_cols and "public_domain" not in settings_cols:
                    db.session.execute(db.text("ALTER TABLE app_settings ADD COLUMN public_domain VARCHAR(255)"))
                    db.session.commit()
        except Exception:
            db.session.rollback()

    @login_manager.user_loader
    def load_user(user_id: str):
        return db.session.get(User, int(user_id))

    # CLI
    app.cli.add_command(init_db_command)

    # Blueprints
    from .routes.auth import bp as auth_bp
    from .routes.admin import bp as admin_bp
    from .routes.company import bp as company_bp
    from .routes.display import bp as display_bp
    from .routes.api import bp as api_bp

    app.register_blueprint(auth_bp)
    app.register_blueprint(admin_bp)
    app.register_blueprint(company_bp)
    app.register_blueprint(display_bp)
    app.register_blueprint(api_bp)

    # Home
    from flask import redirect, url_for
    from flask_login import current_user

    @app.get("/")
    def index():
        if not current_user.is_authenticated:
            return redirect(url_for("auth.login"))
        if current_user.is_admin:
            return redirect(url_for("admin.dashboard"))
        return redirect(url_for("company.dashboard"))

    @app.errorhandler(RequestEntityTooLarge)
    def handle_request_too_large(e):
        """Return a user-friendly message when uploads exceed MAX_CONTENT_LENGTH."""
        # Keep behavior consistent with our AJAX endpoints.
        wants_json = (
            (request.headers.get("X-Requested-With") == "XMLHttpRequest")
            or ("application/json" in (request.headers.get("Accept") or ""))
            or request.is_json
            or (request.form.get("response") == "json")
        )

        msg = "Upload too large. Videos must be 250MB or smaller."
        if wants_json:
            return jsonify({"ok": False, "error": msg}), 413

        # For non-AJAX form posts, redirect back with a flash message.
        from flask import flash, redirect

        flash(msg, "danger")
        return redirect(request.referrer or url_for("company.dashboard")), 413

    return app