# Movie Night Consensus Picker

> Everyone ranks the films, vetoes count: Borda, approval, runoff and Condorcet decide. List the candidate films (or restaurants, games, holiday spots), then let each person rank them and veto the ones they cannot stand. The picker runs four voting methods — Borda count, approval, instant-runoff and Condorcet/Schulze — shows each winner and why, and breaks ties fairly with a seed.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://movienightconsensuspicker.usefulweb.site/ (interactive tool at https://movienightconsensuspicker.usefulweb.site/tool)
- JSON API: POST https://movienightconsensuspicker.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://movienightconsensuspicker.usefulweb.site/api/v1/tool)
- OpenAPI: https://movienightconsensuspicker.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://movienightconsensuspicker.usefulweb.site/mcp - tool `movie_night_consensus_picker`

## Inputs
- candidates (list, required): Candidates (one per line)
- ballots (table, required): Ballots
- vetoMode (select): Vetoes
- approvalCount (integer): Approval: top N of each ranking count as approved - Empty = half of the candidates, rounded up.
- seed (text): Tie-break seed (optional) - Ties are broken by a seeded random order of the candidates. Empty = derived from the inputs.

## Method
- Each ballot is a ranking, best first; films a person leaves out count as tied below all films they ranked. Names are matched case-insensitively; unknown names are reported and skipped.
- Vetoes: in “remove” mode every film vetoed by at least one person is struck before any counting (if that would remove all films, vetoes are ignored and a warning is shown).
- Borda: with n films, 1st place earns n−1 points, 2nd n−2, … ; unranked films share the remaining points equally. Approval: each voter approves their top N films; most approvals wins. Instant-runoff (IRV): count first preferences, eliminate the film with the fewest, transfer those ballots to their next choice, repeat until one film has a majority of the ballots still in play.
- Condorcet/Schulze: for every pair, count how many voters prefer each. A Condorcet winner beats every other film head-to-head. The Schulze method (strongest paths) always finds a winner and agrees with the Condorcet winner when one exists.
- Ties are broken with a random order of the films drawn from the seed (sfc32 seeded with SHA-256), shown in the result, so the outcome is reproducible and nobody can claim favouritism. The recommendation is the Schulze winner.