RollCalcPython/PROJECT_KNOWLEDGE.md

PROJECT_KNOWLEDGE.md

Project-specific technical and domain knowledge for RollCalcPython.

Purpose

RollCalcPython is an internal roll calculator for Naue roll products. The backend is a minimal Flask application that provides authentication, routing, static file delivery, and access logs. Most domain behavior runs in the browser inside templates/roll_calculator.html.

The tool is not intended as an unchecked source of truth. Inputs and outputs must be checked for plausibility before operational use.

Current Architecture

Backend:

• app.py creates the Flask app.
• HTTP Basic Auth is implemented with Flask-HTTPAuth.
• Users are configured in local deployment file config/users.json with Werkzeug password hashes. This file is ignored by Git.
• / renders the active calculator template.
• /help renders the authenticated Help landing page.
• /help/user-manual renders docs/de/user_manual.md server-side inside the RollCalc Help layout.
• /help/recent-changes renders docs/de/recent_changes.md server-side inside the RollCalc Help layout.
• /help/user-manual/screenshots/<path:filename> serves German manual screenshots from docs/de/screenshots/.
• /static/<path:filename> is intended to serve static files behind Basic Auth.
• /api/health returns health/version information.
• /api/user returns the authenticated user.
• Access events are appended to access_log.json.
• build_info.json is loaded at startup and exposed to all templates as build_info.

Frontend:

• templates/roll_calculator.html is the active application page.
• The page contains most CSS and JavaScript inline.
• window.ARTICLE_DATA is loaded from /static/article-data.json.
• window.APP_CONFIG is currently defined inline for forklift rules.
• A disclaimer modal blocks use until the user checks the confirmation checkbox.
• The footer displays build metadata: version, branch, commit, and timestamp.

Build Info

Build/deployment metadata is read from:

build_info.json

Expected fields:

• version
• branch
• commit
• timestamp

If build_info.json is missing, malformed, or does not contain a usable value, RollCalc falls back to unknown for that value and continues serving the site.

The data is loaded centrally in app.py and made available to every template as build_info.

Help and User Manual

The in-app Help area keeps docs/de/user_manual.md as the leading German documentation source. RollCalc reads the Markdown file on each /help/user-manual request and renders it server-side with markdown-it-py.

The documentation structure is prepared for language-specific manuals:

docs/
  de/
    user_manual.md
    screenshots/

Additional languages can follow the same structure later. The current public route still opens the German manual and no language switcher is implemented.

Rendering rules:

• Raw HTML from the Markdown source is disabled.
• Heading ids and the table of contents are generated from the Markdown content.
• Relative image references such as screenshots/disclaimer.png are rewritten to the authenticated manual screenshot route.
• Screenshots belong in the active language's screenshots/ directory, currently docs/de/screenshots/; the screenshot route must remain limited to that directory.

The Help pages use the same HTTP Basic Auth protection as the calculator.

Recent Changes and What's New

Full user-facing release notes are maintained in:

docs/de/recent_changes.md

The calculator header links directly to /help/user-manual. The Help landing page lists only existing documents, currently User Manual and Recent Changes.

The startup What's New dialog uses build_info.version and is suppressed when the version is empty or unknown. The last acknowledged version is stored only in browser localStorage under:

rollcalc_last_seen_version

The short dialog item list is maintained separately in:

static/recent_changes.json

This JSON is a compact summary for the dialog, not the complete release history. Keep it aligned with the most relevant current entries from docs/de/recent_changes.md.

Authentication

RollCalc uses HTTP Basic Auth. User entries are stored in the local deployment file:

config/users.json

This file is intentionally ignored by Git. The versioned file config/users.example.json documents the JSON format only and must not contain real usernames, hashes, or passwords.

The file stores username-to-password-hash mappings:

{
  "username": "<hash>"
}

Password verification uses werkzeug.security.check_password_hash. Users are managed with:

python3 scripts/manage_users.py

The management tool provides a text menu for listing users, creating users, changing passwords, and deleting users. New hashes use the existing RollCalc method pbkdf2:sha256:600000.

The Flask app requires a readable, valid, non-empty config/users.json at startup and does not silently create an empty user file. If the file is missing or invalid, startup should fail with a message pointing to python3 scripts/manage_users.py.

Passwords must not be logged. Password hashes should only be stored in config/users.json or a future protected deployment-specific secret source.

Deployment notes:

• The systemd/service user must be able to read config/users.json.
• Suitable server permissions can be owner martin, group www-data, mode 640, adjusted to the actual deployment users.
• Do not hard-code deployment owners or groups in Python.
• Back up the productive config/users.json before deploying or replacing a server instance.

Roll Geometry

Calculations assume an ideal cylindrical winding.

Assumptions:

• Constant material thickness.
• No compression.
• No air gaps.
• Roll geometry is derived mathematically, not physically measured in the app.

Nominal diameter formula used by the Direct Calculation tab:

D = sqrt(d^2 + (4 * L * 1000 * t) / pi)

Variables:

• D: roll diameter in mm.
• d: core diameter in mm.
• L: product length in m.
• t: material thickness in mm.

When a tolerance/stddev value is present, the UI also displays a -2σ and +2σ diameter range.

Product Length and Extrapolation

Product length from a known diameter is calculated by rearranging the diameter formula:

L = (pi / (4 * t)) * (D^2 - d^2) / 1000

The extrapolation tab estimates a new diameter from a known roll diameter/length pair:

D1 = sqrt(d^2 + (L1 / L0) * (D0^2 - d^2))

Variables:

• D0: known/measured roll diameter.
• L0: known/measured roll length.
• L1: target length.
• D1: extrapolated roll diameter.

Roll Weight

Roll weight is calculated client-side when width, area weight, and length are available:

weight_kg = area_weight_g_m2 * length_m * width_m / 1000

Material thickness and area weight values are loaded from article data and are generated automatically. They are not guaranteed to be complete or reviewed.

Article Data

Active data source:

static/article-data.json

The UI expects article records with fields such as:

• nr
• name
• thickness
• thickness_stddev
• area_weight
• area_weight_stddev
• core_type

Observed additional fields include min/max/count values for material thickness and area weight.

Important data rule:

• Article data is generated from ERP-derived sources.
• These values should not be manually changed unless the task is explicitly data maintenance.

Known domain caveat from existing project notes:

• For articles in the groups Secugrid, Combigrid, Carbofol MF/MF, Carbofol F/F, Carbofol s/F, and Carbofol BF/s, the thickness from article-data.json must not be used without domain validation.

Forklift and Heavy-Roll Rules

The active template currently evaluates forklift warnings through checkForklift() and inline window.APP_CONFIG.

Current inline rule behavior:

• Applies to category bentofix.
• Warning threshold: 1700 kg.
• Hard limit: 2750 kg.
• Minimum core outer diameter: 170 mm.

There is also a richer JSON configuration in:

static/config.json

That file includes localized messages and additional equipment requirements. Before changing forklift behavior, verify whether the active inline config or the static JSON should be authoritative.

Load Optimizer

The Load Optimizer is implemented inline in templates/roll_calculator.html.

Classes:

• LoadOptimizer
• LoadOptimizerUI

It uses calculated roll data from the Direct Calculation tab:

• Roll diameter.
• Core diameter.
• Roll width.
• Roll weight.
• Product length.
• Square meters per roll.

It supports transport presets:

• 20ft Container.
• 40ft Container.
• 40ft High Cube.
• LKW Sattelzug.
• LKW Tandem.

It calculates limiting scenarios by:

• Weight.
• Volume.
• Geometry.

It also draws a side-view SVG visualization.

Disclaimer Gate

The active calculator page includes a disclaimer modal shown after Basic Auth login and before calculator use.

The modal:

• Contains German and English disclaimer text.
• Requires checkbox confirmation.
• Enables the confirmation button only after the checkbox is selected.
• Hides the overlay after confirmation.

This is client-side only. It is not persisted, logged, or enforced server-side.

Admin Area State

RollCalc no longer contains an admin UI or admin API. The previous /admin/logs route and templates/admin.html have been removed.

Login/access logging remains part of RollCalc, but log viewing and article-data administration should not be implemented inside this app. Maintenance of article-data.json is planned for a separate application.

Known Technical Risks

• Password hashes are currently configured in app.py; this should eventually move to a protected external configuration or secrets mechanism.
• Basic Auth only; no sessions or role framework beyond the user dictionary.
• access_log.json is rewritten on every logged request and is not concurrency-safe.
• No log rotation or retention policy is implemented.
• Flask's default static route may conflict with the intended authenticated /static/<path:filename> behavior; verify effective routing before relying on protected static files.
• Most active logic is concentrated in one large HTML template.
• Multiple similar static JavaScript files exist; not all are necessarily active.
• No automated test suite is visible.
• Some docs and filenames in docs/ may reflect earlier package/archive versions.