Shared power system scheme — read-only view

This is the read-only share page. It holds no study of its own and runs no engineering calculation: it displays one frozen snapshot of a scheme (or of an A/B comparison) created when someone pressed the share button. The data path is the share service on the production host: the snapshot is written and signed when the link is created (HMAC signature plus an expiry of permanent, 7 days or 24 hours) and is read back through the share get endpoint, which verifies the signature and the expiry server side and records one visit. A tampered signature or a missing one is rejected explicitly, an expired link reports that it has expired, and an unknown link reports that it does not exist - the page never falls back to showing some other scheme. The share page is also where a customer can send an inquiry, which automatically carries the scheme link so the sales engineer knows which version is being discussed.

A shared link is the hand-over point between engineering and a customer: the customer must be able to open the scheme without an account, see exactly the version that was discussed, and be sure that nobody can edit or forge the numbers. Signing the snapshot and freezing the content is what makes a link quotable in an email or a tender clarification, and the signed link also gives the sales engineer a traceable record of what was sent.

There is no calculation chain here, and no engine study key: the chain is create, then verify, then read. Creating the link takes the scheme (or the two compared schemes) at that moment plus the chosen expiry, writes the frozen snapshot into the share store and returns the identifier, signature and expiry; opening the page sends those three values to the share get endpoint, which verifies the signature against the stored secret, checks the expiry, counts the visit and returns the frozen payload; the page renders the payload read-only. Output = the frozen scheme summary or comparison rows and the signature-verified banner. Linkage: the snapshot content is copied from the scheme library at creation time, so later edits to the scheme, to the tariff or to the study switches do not leak into an already-sent link - a new share is a new snapshot with its own signature and expiry.