package cli

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/lukaszkasprzak/lectio/internal/caldata"
	"github.com/lukaszkasprzak/lectio/internal/calendar"
	"github.com/lukaszkasprzak/lectio/internal/config"
)

// calLayerTemplate is the scaffold written by --cal-new (%s = the layer name).
const calLayerTemplate = `# lectio calendar layer "%[1]s". Add celebrations below, then enable this file
# by adding its name to 'use' in config.ini:  use = %[1]s
# Layers stack over the universal calendar: a [slug] merges over the same slug in
# a lower layer (field by field); a new [slug] adds a celebration.
#
# Fields:
#   date       MM-DD, or easter±N / christmas±N / sunday-after MM-DD
#   rank       solemnity | feast | memorial | optional
#   class      lord | bvm | saint            (precedence tiebreak)
#   colour     white | red | green | violet | rose | black
#   name.<lang>   e.g. name.en, name.pl, name.la
#   reading.<part>   part = first | psalm | second | acclamation | gospel (a citation)
#   suppress = true   remove a celebration inherited from a lower layer

[layer]
id = %[1]s
name = %[1]s
type = diocesan

# Example (edit or delete):
[st-example]
date = 06-15
rank = solemnity
class = saint
colour = white
name.en = Saint Example, Patron
reading.gospel = Jn 10:11-16
`

// calDumpHeader precedes a --cal-dump file. %[1]s = the layer name, %[2]s = a
// human label for the form (e.g. "Ordinary Form").
const calDumpHeader = `# lectio calendar layer "%[1]s" -- the %[2]s universal calendar, DUMPED and
# fully COMMENTED OUT. As shipped it changes nothing. To alter one day, uncomment
# its block, edit a field (rank, colour, name, ...), then enable the layer by
# adding its name to 'use' in config.ini:  use = %[1]s
#
# A layer OVERLAYS the base calendar field by field, so every day you leave
# commented keeps its default. You can also:
#   * remove a celebration:  uncomment its block, add   suppress = true
#   * add one:               write a new [your-slug] with date/rank/colour/name.*
#   * change its readings:   add reading.first / reading.psalm / reading.gospel
#
# Fields: date = MM-DD (or easter+-N / christmas+-N / sunday-after MM-DD) ;
#         rank = solemnity|feast|memorial|optional ; class = lord|bvm|saint ;
#         colour = white|red|green|violet|rose|black ; name.<lang> = display name.
# (reading.* lines are omitted here; add them only to change a day's readings.)
#
# Re-dump anytime with:  lectio --cal-dump %[1]s   (add -l trad for the 1962 form).

[layer]
id = %[1]s
name = %[1]s
type = diocesan
`

var validRanks = map[string]bool{"solemnity": true, "feast": true, "memorial": true, "optional": true}

// runCalDump writes the running universal calendar for a form to
// <CalendarsDir>/<name>.ini as a fully-commented layer template: every
// celebration present, all commented, so uncommenting and editing one day
// overrides it. It refuses to overwrite an existing file. formFlag ("old"/"new",
// optional) overrides the form implied by cfg.
func runCalDump(cfg config.Config, name, formFlag string, stdout, stderr io.Writer) int {
	sel := cfg.Selection()
	if formFlag != "" {
		if formFlag != "old" && formFlag != "new" {
			fmt.Fprintf(stderr, "lectio: invalid --form %q (want old|new)\n", formFlag)
			return 2
		}
		sel.Form = formFlag
	}
	path, err := layerPath(name)
	if err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 2
	}
	if _, err := os.Stat(path); err == nil {
		fmt.Fprintf(stderr, "lectio: %s already exists (not overwriting)\n", path)
		return 1
	}

	base := caldata.Base(sel.Form)
	formLabel := "Ordinary Form"
	if sel.Form == "old" {
		formLabel = "Extraordinary Form (1962)"
	}

	// Sort by date then slug. MM-DD dates sort chronologically and ahead of the
	// movable specs (easter+N, christmas-N), which then group alphabetically.
	slugs := make([]string, 0, len(base.Cels))
	for slug := range base.Cels {
		slugs = append(slugs, slug)
	}
	sort.Slice(slugs, func(i, j int) bool {
		di, dj := base.Cels[slugs[i]].Fields["date"], base.Cels[slugs[j]].Fields["date"]
		if di != dj {
			return di < dj
		}
		return slugs[i] < slugs[j]
	})

	var b strings.Builder
	fmt.Fprintf(&b, calDumpHeader, name, formLabel)
	order := []string{"date", "rank", "class", "colour", "name.en", "name.pl", "name.la"}
	n := 0
	for _, slug := range slugs {
		f := base.Cels[slug].Fields
		if f["date"] == "" {
			continue // skip anything without a date (defensive)
		}
		b.WriteByte('\n')
		fmt.Fprintf(&b, "# [%s]\n", slug)
		for _, k := range order {
			if v := f[k]; v != "" {
				fmt.Fprintf(&b, "# %s = %s\n", k, v)
			}
		}
		n++
	}

	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 1
	}
	if err := os.WriteFile(path, []byte(b.String()), 0o644); err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 1
	}
	fmt.Fprintf(stdout, "dumped %d %s celebrations to %s\n", n, formLabel, path)
	fmt.Fprintf(stdout, "uncomment a day, edit it, then set  use = %s  in config.ini\n", name)
	return 0
}

// layerPath resolves <CalendarsDir>/<name>.ini, rejecting a name with path separators.
func layerPath(name string) (string, error) {
	if name == "" || strings.ContainsAny(name, `/\`) {
		return "", fmt.Errorf("invalid layer name %q", name)
	}
	dir, err := config.CalendarsDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, name+".ini"), nil
}

// runCalNew scaffolds a new calendar-layer file and exits. It refuses to
// overwrite an existing file.
func runCalNew(name string, stdout, stderr io.Writer) int {
	path, err := layerPath(name)
	if err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 2
	}
	if _, err := os.Stat(path); err == nil {
		fmt.Fprintf(stderr, "lectio: %s already exists (not overwriting)\n", path)
		return 1
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 1
	}
	if err := os.WriteFile(path, []byte(fmt.Sprintf(calLayerTemplate, name)), 0o644); err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 1
	}
	fmt.Fprintf(stdout, "created %s\n", path)
	fmt.Fprintf(stdout, "edit it, then set  use = %s  in config.ini\n", name)
	return 0
}

// runCalCheck validates a calendar-layer file (dates resolve, ranks/colours/
// classes are known) and exits non-zero if it finds problems.
func runCalCheck(name string, stdout, stderr io.Writer) int {
	path, err := layerPath(name)
	if err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 2
	}
	layer, err := caldata.LoadLayer(path, name)
	if err != nil {
		fmt.Fprintln(stderr, "lectio:", err)
		return 1
	}
	slugs := make([]string, 0, len(layer.Cels))
	for s := range layer.Cels {
		slugs = append(slugs, s)
	}
	sort.Strings(slugs)

	problems := 0
	report := func(slug, msg string) {
		problems++
		fmt.Fprintf(stdout, "  [%s] %s\n", slug, msg)
	}
	for _, slug := range slugs {
		f := layer.Cels[slug].Fields
		if f["suppress"] == "true" {
			continue // a removal needs no other fields
		}
		switch d := f["date"]; {
		case d == "":
			report(slug, "missing date")
		case !calendar.ValidDate(calendar.DateSpec(d)):
			report(slug, fmt.Sprintf("unparseable date %q", d))
		}
		if r := f["rank"]; r != "" && !validRanks[r] {
			report(slug, fmt.Sprintf("unknown rank %q (want solemnity|feast|memorial|optional)", r))
		}
		if c := f["colour"]; c != "" && calendar.ParseColour(c) == "" {
			report(slug, fmt.Sprintf("unknown colour %q", c))
		}
		if cl := f["class"]; cl != "" && cl != "lord" && cl != "bvm" && cl != "saint" {
			report(slug, fmt.Sprintf("unknown class %q (want lord|bvm|saint)", cl))
		}
	}
	if problems > 0 {
		fmt.Fprintf(stderr, "lectio: %s: %d problem(s)\n", path, problems)
		return 1
	}
	fmt.Fprintf(stdout, "ok: %s (%d celebrations)\n", path, len(layer.Cels))
	return 0
}