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ffx/requirements/shifted_seasons_handling.md
2026-04-12 17:12:32 +02:00

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Shifted Seasons Handling

This file defines the behavioral contract for mapping source season and episode numbering to target season and episode numbering through stored shifted-season rules.

Primary sources:

  • requirements/project.md
  • requirements/architecture.md
  • actual tool code in src/ffx/

Secondary source:

  • SCRATCHPAD.md, used only to clarify current hardening gaps and not as the primary contract source.

Scope

  • Persisting shifted-season rules in SQLite.
  • Allowing shifted-season rules to be attached either to a show or to a specific pattern.
  • Selecting at most one active shifted-season rule for one concrete source season and episode tuple.
  • Applying additive season and episode offsets to produce target numbering.
  • Using shifted target numbering during convert for TMDB episode lookup and generated season and episode filename tokens.
  • Managing show-level default mappings and pattern-level override mappings from the Textual editing workflows.

Out Of Scope

  • General filename parsing rules for detecting season and episode values.
  • Standalone rename command behavior, which currently uses explicit rename inputs rather than stored shifted-season rules.
  • Stream or track mapping behavior unrelated to season and episode numbering.

Terms

  • shifted-season rule: one persisted row describing how one source-numbering range maps to target numbering through additive offsets.
  • show-level shifted-season rule: a rule attached directly to a show and used as the fallback mapping layer for that show.
  • pattern-level shifted-season rule: a rule attached directly to a pattern and used as the override mapping layer for that pattern.
  • source numbering: the season and episode values detected from the current source file or supplied as source-side conversion inputs before shifting.
  • target numbering: the season and episode values after one active shifted-season rule has been applied.
  • original season: the source-domain season number a shifted-season rule is eligible to match.
  • episode range: the optional source-domain episode interval covered by one shifted-season rule.
  • open bound: an unbounded start or end of the episode range. Current storage uses -1 as the internal sentinel for an open bound.
  • active shifted-season rule: the single rule selected for one concrete input after precedence resolution.
  • identity mapping: the default 1:1 outcome where source numbering is used unchanged.

Rules

  • SHIFTED_SEASONS_HANDLING-0001: The domain model shall allow a shifted-season rule to be owned by exactly one of:
    • one show
    • one pattern
  • SHIFTED_SEASONS_HANDLING-0002: A single shifted-season rule shall not belong to both a show and a pattern at the same time.
  • SHIFTED_SEASONS_HANDLING-0003: A shifted-season rule shall carry these fields: original_season, first_episode, last_episode, season_offset, and episode_offset.
  • SHIFTED_SEASONS_HANDLING-0004: season_offset and episode_offset shall be additive signed integers applied to matched source numbering to produce target numbering.
  • SHIFTED_SEASONS_HANDLING-0005: A shifted-season rule shall match a source tuple only when:
    • the source season equals original_season
    • the source episode is greater than or equal to first_episode when the lower bound is closed
    • the source episode is less than or equal to last_episode when the upper bound is closed
  • SHIFTED_SEASONS_HANDLING-0006: An open lower or upper episode bound shall represent an unbounded side of the covered source episode range.
  • SHIFTED_SEASONS_HANDLING-0007: If one shifted-season rule matches, target numbering shall be:
    • target season = source season + season_offset
    • target episode = source episode + episode_offset
  • SHIFTED_SEASONS_HANDLING-0008: If no shifted-season rule matches, source numbering shall pass through unchanged.
  • SHIFTED_SEASONS_HANDLING-0009: Shifted-season handling shall operate in a source-to-target numbering model. Stored rules map detected source numbering to the target numbering used by conversion-facing metadata and output naming.
  • SHIFTED_SEASONS_HANDLING-0010: Pattern matching identifies the owning show and optionally a more specific owning pattern. Resolution of the active shifted-season rule shall use this precedence order:
    • matching pattern-level rule
    • matching show-level rule
    • identity mapping
  • SHIFTED_SEASONS_HANDLING-0011: At most one shifted-season rule may be active for one concrete source season and episode tuple. Shifted-season rules shall never stack or compose.
  • SHIFTED_SEASONS_HANDLING-0012: Within one owner scope, shifted-season rules shall not overlap in their effective episode coverage for the same original_season.
  • SHIFTED_SEASONS_HANDLING-0013: If a shifted-season rule uses two closed episode bounds, last_episode shall be greater than or equal to first_episode.
  • SHIFTED_SEASONS_HANDLING-0014: Shifted-season rule evaluation shall be deterministic. Released behavior shall not depend on arbitrary database row order when invalid overlapping rules exist.
  • SHIFTED_SEASONS_HANDLING-0015: A pattern-level rule is permitted to map to zero offsets. Such a rule is a valid explicit override that beats show-level fallback and produces identity mapping for its covered source range.
  • SHIFTED_SEASONS_HANDLING-0016: During convert, when show, season, and episode values are available and stored shifting is active, the shifted target numbering shall drive:
    • TMDB episode lookup
    • season and episode filename tokens such as S01E02
    • generated episode basenames that include season and episode numbering
  • SHIFTED_SEASONS_HANDLING-0017: When conversion is supplied explicit target-domain season or episode values for TMDB naming, the system shall not apply stored shifting on top of those already-targeted values.
  • SHIFTED_SEASONS_HANDLING-0018: Operator-facing editing shall expose shifted-season rule management in both of these places:
    • show editing for show-level default mappings
    • pattern editing for pattern-level override mappings
  • SHIFTED_SEASONS_HANDLING-0019: User-facing shifted-season editing should present open episode bounds as a natural empty-state input rather than forcing operators to type the internal sentinel directly.

Acceptance

  • A show can exist with zero or more show-level shifted-season rules.
  • A pattern can exist with zero or more pattern-level shifted-season rules.
  • A shifted-season rule is stored against exactly one owner scope.
  • A source tuple matching a pattern-level rule yields target numbering from that rule even when a matching show-level rule also exists.
  • A source tuple matching no pattern-level rule but matching a show-level rule yields target numbering from the show-level rule.
  • A source tuple matching neither scope yields identity mapping.
  • A pattern-level zero-offset rule can explicitly override a nonzero show-level rule for the same covered source range.
  • Two shifted-season rules for the same owner scope and original season cannot both be valid if they cover overlapping episode ranges.
  • During convert, shifted numbering is what TMDB episode lookup and generated season and episode tokens see when stored shifting is active.
  • The TUI can display and maintain shifted-season rules from both the show and pattern editing flows.

Current Code Fit

  • src/ffx/model/show.py and src/ffx/model/pattern.py now both expose shifted-season relationships, and src/ffx/model/shifted_season.py stores each rule against exactly one owner scope through show_id or pattern_id.
  • src/ffx/shifted_season_controller.py now resolves mappings with pattern-over-show precedence and applies at most one active rule for a source tuple.
  • src/ffx/show_details_screen.py, src/ffx/shifted_season_details_screen.py, and src/ffx/shifted_season_delete_screen.py provide reusable shifted-season editing dialogs, and src/ffx/pattern_details_screen.py now exposes the pattern-level override flow.
  • src/ffx/cli.py now resolves shifted numbering during convert from: pattern-level match, then show-level match, then identity mapping.
  • src/ffx/database.py now migrates version-2 databases to version 3 by preserving existing show-level rows and extending the schema for pattern-level ownership.

Risks

  • The current CLI groups --show, --season, and --episode under one override bucket used for TMDB-related behavior. Source-domain versus target-domain semantics of each override must stay documented clearly so stored shifting is neither skipped nor double-applied unexpectedly.
  • Existing version-2 databases only contain show-owned shifted-season rows, so a version-3 migration must preserve those rows as the show-level fallback layer.
  • Current modern automated test coverage for shifted-season behavior is light, so precedence, migration, and convert-time numbering behavior need focused tests.