Refactor schedule_parser: split 1163-line file into focused modules

[Copilot]

pkg/parser/schedule_parser.go exceeded healthy size limits at 1163 lines, mixing cron detection, fuzzy scheduling, time parsing, and parser orchestration in a single file.

Changes

Split into three focused modules:

• schedule_cron_detection.go (140 lines): Cron pattern detection and validation

  • IsDailyCron, IsHourlyCron, IsWeeklyCron, IsFuzzyCron, IsCronExpression

• schedule_fuzzy_scatter.go (319 lines): Deterministic time distribution for fuzzy schedules

  • ScatterSchedule with support for DAILY, HOURLY, WEEKLY, BI_WEEKLY, TRI_WEEKLY patterns
  • stableHash for consistent workflow time assignment

• schedule_time_utils.go (245 lines): Time parsing and conversion utilities

  • parseTime, parseTimeToMinutes, mapWeekday, parseUTCOffset, parseHourMinute
  • Timezone normalization helpers

Main file reduced: 1163 → 512 lines (56% reduction)

Each module includes:

• Dedicated test file with comprehensive coverage
• Focused logger for debugging
• Clear responsibility boundary

All existing tests pass without modification. Public API unchanged.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[file-diet] Refactor Large Go File: pkg/parser/schedule_parser.go (1084 lines)</issue_title>
<issue_description>### Overview

The file pkg/parser/schedule_parser.go has grown to 1084 lines, significantly exceeding the healthy 800-line threshold. While it has excellent test coverage (2031 test lines, ~1.87 ratio), the file's size makes it difficult to navigate and maintain. This task involves refactoring it into smaller, focused modules with clear boundaries.

Current State

• File: pkg/parser/schedule_parser.go
• Size: 1084 lines
• Test Coverage: 2031 lines in schedule_parser_test.go (~1.87 ratio)
• Complexity: High - contains 5 distinct functional areas mixed together

Problem Analysis

The file mixes multiple concerns:

1. Cron detection - Pattern matching for different cron types
2. Fuzzy scattering - Complex deterministic time distribution (290+ lines in ScatterSchedule)
3. Parser orchestration - Tokenization and high-level parsing
4. Expression parsing - Interval and base schedule parsing
5. Time utilities - Time parsing and conversion helpers

Refactoring Strategy

Split the file into focused modules aligned with functional boundaries:

1. schedule_cron_detection.go (~150 lines)

Functions to move:

• IsDailyCron(cron string) bool
• IsHourlyCron(cron string) bool
• IsWeeklyCron(cron string) bool
• IsFuzzyCron(cron string) bool
• IsCronExpression(input string) bool

Responsibility: Cron pattern detection and classification

Rationale: These are pure functions that analyze cron strings. They have no dependencies on the parser state and can be tested independently.

2. schedule_fuzzy_scatter.go (~320 lines)

Functions to move:

• ScatterSchedule(fuzzyCron, workflowIdentifier string) (string, error) (290+ lines)
• stableHash(s string, modulo int) int

Responsibility: Deterministic fuzzy schedule time distribution

Rationale: The ScatterSchedule function is self-contained with complex logic for different fuzzy patterns (DAILY, HOURLY, WEEKLY, etc.). Extracting it reduces the main file by ~30%.

3. schedule_time_utils.go (~150 lines)

Functions to move:

• parseTime(timeStr string) (minute string, hour string) (120 lines)
• parseTimeToMinutes(hourStr, minuteStr string) int
• mapWeekday(day string) string

Responsibility: Time parsing and conversion utilities

Rationale: These are helper functions used by the parser but don't depend on parser state. Can be reused by other modules.

4. schedule_parser_core.go (~250 lines)

Keep in this file:

• ScheduleParser struct
• ParseSchedule(input string) (cron, original, error) (entry point)
• (p *ScheduleParser) tokenize() error
• (p *ScheduleParser) parse() (string, error)

Responsibility: High-level parsing orchestration

Rationale: This is the main API surface. Keeping it focused on orchestration makes the flow clear.

5. schedule_parser_expressions.go (~250 lines)

Functions to move:

• (p *ScheduleParser) parseInterval() (string, error) (150+ lines)
• (p *ScheduleParser) parseBase() (string, error) (180+ lines)
• (p *ScheduleParser) extractTime(startPos int) (string, error)
• (p *ScheduleParser) extractTimeBetween(startPos, endPos int) (string, error)
• (p *ScheduleParser) extractTimeAfter(startPos int) (string, error)

Responsibility: Schedule expression parsing (interval, base, time extraction)

Rationale: These are the detailed parsing methods that consume tokens. They depend on parser state but can be in a separate file via schedule_parser_core.go.

Implementation Plan

Step-by-step refactoring approach

1. Create test infrastructure first

   • Run make test-unit to establish baseline
   • Ensure all existing tests pass before changes

2. Extract utilities (no dependencies)

   • Create schedule_time_utils.go with time parsing functions
   • Create schedule_time_utils_test.go with relevant tests
   • Run tests to verify behavior unchanged

3. Extract detection functions

   • Create schedule_cron_detection.go with Is*Cron functions
   • Create schedule_cron_detection_test.go with relevant tests
   • Run tests to verify behavior unchanged

4. Extract fuzzy scattering

   • Create schedule_fuzzy_scatter.go with ScatterSchedule and stableHash
   • Create schedule_fuzzy_scatter_test.go with relevant tests
   • Run tests to verify behavior unchanged

5. Split parser methods

   • Create schedule_parser_expressions.go with parsing methods
   • Move parseInterval, parseBase, extractTime* methods
   • Ensure methods can still access ScheduleParser receiver
   • Run tests to verify behavior unchanged

6. Rename original file

   • Rename schedule_parser.go to schedule_parser_core.go
   • Keep only core orch...

• Fixes [file-diet] Refactor Large Go File: pkg/parser/schedule_parser.go (1084 lines) #11285

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.