Oliver Jakoubek
f748b0e134
- Initialize go.mod with module path code.beautifulmachines.dev/quando - Set Go version to 1.22+ (using 1.25.6) - Create directory structure (internal/calc/, .github/workflows/) - Add comprehensive README.md with project overview, features, and examples - Add MIT LICENSE - Populate .gitignore for Go projects - Create GitHub Actions CI workflow for testing, linting, and benchmarking All acceptance criteria met: ✓ go.mod initialized with correct module path ✓ Go 1.22+ specified in go.mod ✓ Directory structure created ✓ README.md with project overview ✓ LICENSE file (MIT) ✓ .gitignore for Go projects ✓ Basic CI/CD workflow
155 lines
4.1 KiB
Markdown
155 lines
4.1 KiB
Markdown
# quando
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> Intuitive and idiomatic date calculations for Go
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**quando** is a standalone Go library for complex date operations that are cumbersome or impossible with the Go standard library alone. It provides a fluent API for date arithmetic, parsing, formatting, and timezone-aware calculations.
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## Features
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- **Fluent API**: Chain operations naturally: `quando.Now().Add(2, Months).StartOf(Week)`
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- **Month-End Aware**: Handles edge cases like `Jan 31 + 1 month = Feb 28`
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- **DST Safe**: Calendar-based arithmetic (not clock-based)
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- **Zero Dependencies**: Only Go stdlib
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- **Immutable**: Thread-safe by design
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- **i18n Ready**: Multilingual formatting (EN, DE in Phase 1)
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- **Testable**: Built-in Clock abstraction for deterministic tests
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## Installation
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```bash
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go get code.beautifulmachines.dev/quando
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```
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## Quick Start
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```go
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import "code.beautifulmachines.dev/quando"
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// Get current date
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now := quando.Now()
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// Date arithmetic with month-end handling
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date := quando.From(time.Date(2026, 1, 31, 0, 0, 0, 0, time.UTC))
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result := date.Add(1, quando.Months) // Feb 28, 2026 (not overflow)
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// Snap to boundaries
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monday := quando.Now().StartOf(quando.Week) // This week's Monday 00:00
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endOfMonth := quando.Now().EndOf(quando.Month) // Last day of month 23:59:59
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// Next/Previous dates
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nextFriday := quando.Now().Next(time.Friday)
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prevMonday := quando.Now().Prev(time.Monday)
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// Differences
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duration := quando.Diff(startDate, endDate)
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months := duration.Months()
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humanReadable := duration.Human() // "2 years, 3 months, 5 days"
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// Parsing (automatic format detection)
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date, err := quando.Parse("2026-02-09")
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date, err := quando.Parse("09.02.2026") // EU format
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date, err := quando.Parse("3 days ago") // Relative
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// Formatting
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date.Format(quando.ISO) // "2026-02-09"
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date.Format(quando.Long) // "February 9, 2026"
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date.FormatLayout("02 Jan") // "09 Feb"
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// Timezone conversion
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utc := date.InTimezone("UTC")
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berlin := date.InTimezone("Europe/Berlin")
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// Date inspection
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week := date.WeekNumber() // ISO 8601 week number
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quarter := date.Quarter() // 1-4
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dayOfYear := date.DayOfYear() // 1-366
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```
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## Core Concepts
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### Month-End Overflow Handling
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When adding months, if the target day doesn't exist, quando snaps to the last valid day:
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```go
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jan31 := quando.From(time.Date(2026, 1, 31, 0, 0, 0, 0, time.UTC))
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feb28 := jan31.Add(1, quando.Months) // Feb 28, not March 3
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```
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### DST-Aware Arithmetic
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Adding days means "same time on next calendar day", not "24 hours later":
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```go
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// During DST transition (23-hour day)
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date := quando.From(time.Date(2026, 3, 31, 2, 0, 0, 0, cetLocation))
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next := date.Add(1, quando.Days) // April 1, 2:00 CEST (not 3:00)
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```
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### Immutability
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All operations return new instances. Original values are never modified:
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```go
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original := quando.Now()
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modified := original.Add(1, quando.Days)
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// original is unchanged
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```
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## Testing
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quando provides a `Clock` interface for deterministic tests:
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```go
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// In production
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date := quando.Now()
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// In tests
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fixedTime := time.Date(2026, 2, 9, 12, 0, 0, 0, time.UTC)
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clock := quando.NewFixedClock(fixedTime)
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date := clock.Now() // Always returns Feb 9, 2026
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```
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## Requirements
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- Go 1.22 or later
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- No external dependencies
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## Documentation
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Full documentation available at: [pkg.go.dev/code.beautifulmachines.dev/quando](https://pkg.go.dev/code.beautifulmachines.dev/quando)
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## License
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MIT License - see [LICENSE](LICENSE) file for details.
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## Contributing
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Contributions welcome! Please ensure:
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- Tests pass (`go test ./...`)
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- Code is formatted (`go fmt ./...`)
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- No vet warnings (`go vet ./...`)
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- Coverage ≥95% for new code
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## Roadmap
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### Phase 1 (Current)
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- ✅ Project setup
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- 🚧 Core date operations
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- 🚧 Parsing and formatting
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- 🚧 Timezone handling
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- 🚧 i18n (EN, DE)
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### Phase 2
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- Date ranges and series
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- Batch operations
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- Performance optimizations
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### Phase 3
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- Holiday calendars
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- Business day calculations
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- Extended language support
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## Acknowledgments
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Inspired by [Moment.js](https://momentjs.com/), [Carbon](https://carbon.nesbot.com/), and [date-fns](https://date-fns.org/), but designed to be idiomatic Go.
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