Add COPEN transition plans, with COPEN to CTFYS as the first

[cohm]

Starts #66. First slice: the plumbing, plus COPEN → CTFYS as the worked example.

A COPEN student takes one common year and then transfers into a five-year programme, so what they actually study is published nowhere — COPEN's plan stops after year 1, and the target's plan assumes its own year 1. Picking COPEN and then a continuation programme now composes the real thing.

The plan records the difference, not a course list

src/data/transitions.json, one entry per (from, to) pair:

{ "from": "COPEN", "to": "CTFYS", "sourceYears": [1],
  "credited": [{ "code": "SF1626", "replaces": ["SF1674"] },
               { "code": "SF1624", "replaces": ["SF1672"] },
               { "code": "SA1007" }],
  "exempt": [{ "code": "SF1544", "creditedBy": "SF1546" }],
  "added":  [{ "code": "SF1920", "year": 2, "periodCredits": { "P3": 6 },
               "substitutesFor": "SF1922", "fromProgram": "CELTE",
               "cosmeticsGroup": "Matematik" }],
  "verified": false }

(Abridged — there are nine credited entries, six of which name a replaces.) Four kinds of statement: credited (a source course counting toward the target degree, optionally naming the target course it replaces), exempt (a target course credited away), added (a course from neither published plan), and moved (a target course shifted to a later year — unused today, kept because it's the natural shape for "the target's own course, later").

Declarative on purpose: a hand-written combined course list would go stale the moment either programme is re-extracted, and silently — nothing would report that the composition no longer matched. Recording only the difference makes composeTransition a pure function of both programmes' current data. Year numbering needs no adjustment: source year 1 + target years 2–3 already reads 1/2/3.

SF1920 from CELTE, not SF1922 from CTFYS

A COPEN student has no probability course, and CTFYS teaches SF1922 in its year 1, which the transfer student was never present for. #66 suggested taking SF1922 in P4 of year 2 with CTFYS's year-1 students. Taking SF1920 in P3 with CELTE's second year is better on both counts — no waiting until P4, and the credits land in the period the exemption emptied:

composed year 2	P1	P2	P3	P4
SF1922 moved to y2 P4	15	14	10	21
SF1920 from CELTE in P3	15	14	16	15

Both total 60 hp — which is exactly why the load check has to be per period. The residual ±1 is structural: SF1544 carried 1 hp in P2 and 5 in P3, while SF1920 is 6 hp all in P3.

An added course needs its own data, since CELTE isn't in programs.json. It's embedded in the plan in the same raw shape a data file uses and parsed with parseCourseEntries — the loader's own parser, split out for this so the period/credit normalisation isn't reimplemented. SF1920's values were read from the live sources the extractor uses: 6 hp and P3 from CELTE's year-2 plan, TEN1 and the SF1625 prerequisite from its course page. That prerequisite resolves inside the composed plan, since SF1625 is one of the nine COPEN courses — and the arrow is drawn.

cosmeticsGroup turned out to be necessary rather than decorative: without it the course falls to the default colour, which beside the light-tone palette reads as a bug rather than as "this came from elsewhere". SF1920 declares Matematik and now renders identically to CTFYS's other maths courses (verified: same computed fill as SF1681 and SF1683).

Prerequisite arrows follow the course actually taken

A target course in years 2–3 states its prerequisites in the target's own terms — CTFYS's SF1683 and SI1146 both require SF1674. A transfer student never took SF1674; they took SF1626, the same subject. Drawn to the letter, the arrow starts from a course that isn't in their plan and simply vanishes, leaving those courses looking as though they had no prerequisites at all.

So credited is a list of objects that can say what each course replaces, and redirectPrerequisites rewrites every reference through those equivalences — a general rule over the plan's data, not a list of special cases. Exactly five CTFYS year-1 courses are referenced from years 2–3, and all five resolve:

referenced target course	becomes	arrows affected
SF1674 Flervariabelanalys	SF1626	→ SF1683, → SI1146
SF1672 Linjär algebra	SF1624	→ SF1681
DD1331 Grundläggande programmering	DD1310	→ DD1327
SG1112 Mekanik I	SG1133	→ SE1055, → SG1113
SK1104 Klassisk fysik	SK1115	→ SH1014

Three fields feed the same map, so an equivalence is stated once: credited[].replaces, exempt[].creditedBy (SF1546 → SF1544 — which is why SF1546 carries no replaces; the validator caught that redundancy), and added[].substitutesFor.

A reference that survives the rewrite but names a course outside the composed plan is reported: that means an equivalence is missing, and the symptom would otherwise be a silently absent arrow. validate-data checks the same invariant statically, so a missing equivalence fails in CI rather than only in the browser.

Cosmetics have to be merged

The two files share no course codes, so rendering from the target's cosmetics alone drew all nine COPEN courses in the default colour. mergeCosmetics merges by group name — "Matematik" from both becomes one legend row — with the target's colour winning on conflict:

group	CTFYS	COPEN	composed
Matematik	blue	blue	blue
Fysik	green	green	green
Ingenjörsämnen	brick	turquoise	brick (target wins)
Övrigt	yellow	—	yellow
Programmering	—	brick	turquoise (first free family)

A source-only group takes the first unused family rather than its own, because COPEN's Programmering is brick, which CTFYS already spends on Ingenjörsämnen. COPEN+CTFYS lands on exactly five families — the documented hard cap. An overflow is reported and those courses fall back to the default colour.

Full-time load, checked per period

year 1  COPEN      15 / 15 / 15 / 15
year 2  composed   15 / 14 / 16 / 15
year 3  CTFYS      15 / 15 / 15 / 15

A swap can balance across a year while leaving individual periods lopsided, and the year total hides it entirely — so the check is per period, the same signal validate-data applies to the programme files. The ±1 is shown in the UI rather than corrected: where the plan puts a course is the program director's call.

The chart is titled for both programmes

Civilingenjörsutbildning Öppen ingång → Teknisk fysik (COPEN → CTFYS)

The target's name is shortened, because the qualification is identical on both sides and pure noise the second time. shortProgramName strips a fixed set of openers rather than the longest common word prefix — the latter looks more general but is wrong on the English names: "Degree Program in Engineering - Open Entrance" and "Degree Program in Engineering Physics" share "Degree Program in Engineering", which would reduce CTFYS to "Physics". An unrecognised name falls through unchanged.

Verified in both languages, and that a plain programme view is untouched:

view	title
COPEN alone	Civilingenjörsutbildning Öppen ingång (COPEN)
COPEN + CTFYS (sv)	Civilingenjörsutbildning Öppen ingång → Teknisk fysik (COPEN → CTFYS)
COPEN + CTFYS (en)	Degree Program in Engineering - Open Entrance → Engineering Physics (COPEN → CTFYS)
CTFYS alone	Civilingenjörsutbildning i Teknisk fysik (CTFYS)

The SVG <title> used by screen readers picks it up too, with the right year range. The composed code also reaches the export audit stamp (COPEN → CTFYS · build … · date) — wanted; export filenames are fixed strings and unaffected.

Validation

validate-data cross-checks each plan against both programmes, in both directions: credited must match what the source actually teaches in those years — a course added to COPEN that nobody added to the plan would otherwise be dropped silently — and every exempt/moved code must exist in the target with the year the plan claims. verified: false warns, exactly as in programs.json.

Verification

Headless Chrome, ?program=COPEN&continuation=CTFYS:

check	result
years rendered	3 (was 1)
SF1544 (exempt)	absent
SF1922 (CTFYS year 1)	absent — year 1 is COPEN's
SF1920 (added)	present at year 2, P3, in the Matematik colour
SF1625 → SF1920 prerequisite arrow	drawn
COPEN year-1 courses	9/9 present, all coloured
CTFYS year-1-only courses	none leaked through
notice line	names what was credited, dropped and added
load line	shows 15/14/16/15
every arrow from the five year-1 courses	redirected to its COPEN equivalent
arrows still starting from a CTFYS year-1 course	none
COPEN alone	unchanged
console / page errors	none

lint, tsc --noEmit, validate-data --cohorts (0 errors) and the build all clean.

Not done

• Only COPEN → CTFYS, marked verified: false. The other targets (CINEK, CTMAT, …) need their plans in whatever format they arrive; the schema above is what to map them onto, and adding one is a data-only change.
• moved is implemented and validated but unused — CTFYS needs only exempt + added. It stays because "take the target's own course a year later" is a shape other programmes may well need.

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Project	Deployment	Actions	Updated (UTC)
program-visualization	Ready	Preview	Aug 22, 2026 4:08pm