// Package readings is the single entry point the CLI and TUI use to fetch
// a day's readings. It routes between the modern (liturgy) and traditional
// (tradlit) lectionaries by config, then applies part filtering, returning
// source-agnostic liturgy.Section values either way.
package readings

import (
	"strings"

	"github.com/lukaszkasprzak/lectio/internal/config"
	"github.com/lukaszkasprzak/lectio/internal/liturgy"
	"github.com/lukaszkasprzak/lectio/internal/tradlit"
)

// Options controls how Load resolves a day's readings.
type Options struct {
	// Date is the day to load, formatted YYYY-MM-DD.
	Date string
	// Refresh bypasses cache layers and re-fetches from the network
	// (modern lectionary only; see liturgy.Options.Refresh).
	Refresh bool
	// Offline restricts Load to previously cached/harvested data, never
	// hitting the network (both lectionaries; see liturgy.Options.Offline
	// and tradlit.Load's offline parameter).
	Offline bool
	// All, when true, keeps every part the config doesn't explicitly hide;
	// when false, only the gospel is kept.
	All bool
}

// Load fetches the day's sections and its DayInfo (celebration name,
// temporal, liturgical colour -- see liturgy.DayInfo) for the configured
// lectionary (cfg.Lectionary: "traditional" or "new") and applies part
// filtering. Returns liturgy.Section values regardless of source. A source
// that yields no DayInfo (see liturgy.Load/tradlit.Load) comes back as a
// zero liturgy.DayInfo, not an error -- callers omit the header for it.
func Load(cfg config.Config, opts Options) ([]liturgy.Section, liturgy.DayInfo, error) {
	offline := opts.Offline || cfg.Offline

	var secs []liturgy.Section
	var info liturgy.DayInfo
	var err error

	if cfg.Lectionary == "traditional" {
		secs, info, err = tradlit.Load(opts.Date, cfg.TraditionalLang, offline)
	} else {
		secs, info, err = liturgy.Load(liturgy.Options{
			Date:    opts.Date,
			Refresh: opts.Refresh,
			Offline: offline,
		})
	}
	if err != nil {
		return nil, liturgy.DayInfo{}, err
	}

	return filterParts(secs, cfg, opts.All), info, nil
}

// filterParts keeps only the gospel when !all (PartID "ewangelia" modern or
// "evangelium" traditional). When all and the lectionary is traditional, it
// keeps only the scripture readings (isTraditionalReading) -- dropping
// Introit/Kolekta/Graduale/Offertorium/Sekreta/Prefacja/Komunia/Pokomunia
// and any commemoration, none of which are readings; the "new" lectionary
// path is unchanged, keeping sections cfg.PartShown allows (a section with
// an empty PartID is always kept). Pure and network-free.
func filterParts(secs []liturgy.Section, cfg config.Config, all bool) []liturgy.Section {
	var out []liturgy.Section
	for _, s := range secs {
		if !all {
			if s.PartID == "ewangelia" || s.PartID == "evangelium" {
				out = append(out, s)
			}
			continue
		}
		if cfg.Lectionary == "traditional" {
			if isTraditionalReading(s.PartID) {
				out = append(out, s)
			}
			continue
		}
		if s.PartID == "" || cfg.PartShown(cfg.Lectionary, s.PartID) {
			out = append(out, s)
		}
	}
	return out
}

// isTraditionalReading reports whether partID (a lowercased missalemeum
// section id) is a scripture reading -- the gospel, or an epistle/lesson --
// rather than Introit/Kolekta/Graduale/Offertorium/Sekreta/Prefacja/
// Komunia/Pokomunia or a commemoration.
func isTraditionalReading(partID string) bool {
	return partID == "evangelium" ||
		strings.HasPrefix(partID, "lectio") ||
		strings.HasPrefix(partID, "epistola") ||
		strings.HasPrefix(partID, "prophetia")
}