// Package config loads lectio's INI configuration file.
//
// Resolution order: LECTIO_CONFIG env var -> ~/.config/lectio/config.ini
// (auto-seeded from the embedded default on first run, honoring
// XDG_CONFIG_HOME via os.UserConfigDir()) -> built-in defaults. A pre-existing
// config.toml (lectio's former format) at the default location is converted to
// config.ini once, on first run, and left on disk. INI that fails to parse
// falls back to defaults with a warning on stderr.
package config

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

	"github.com/pelletier/go-toml/v2"

	"github.com/lukaszkasprzak/lectio/internal/calendar"
	"github.com/lukaszkasprzak/lectio/internal/ini"
)

// configHeader is the reference comment block written at the top of every
// generated config.ini (the first-run seed and every Save), documenting each
// option's allowed values. Full-line comments only, so the INI reader skips
// them and values stay verbatim.
const configHeader = `# lectio configuration (INI). Full-line comments only (# or ;); no inline comments.
# Lists are comma-separated. Booleans are true/false.
#
# Allowed values:
#   lectionary        new | traditional        (new = modern OF; traditional = 1962 EF)
#   traditional_lang  pl | en                  (vernacular for traditional propers)
#   versions          any of: bt, wuj, vul, grb, drb   (comma list; bt = Biblia Tysiąclecia)
#   default_version   bt | wuj | vul | grb | drb
#   width             integer; 0 = detect terminal width
#   all               true | false             (all readings, or just the gospel)
#   offline           true | false             (never fetch; cache/sigla only)
#   ui_language       en | pl                  (interface chrome; readings stay source-language)
#   sigla_style       auto | polish | english | latin  (citation dialect; auto follows ui_language)
#   web_theme         a theme name (see docs/THEMES.md)
#   web_port          integer; 0 = try 1099, then any free port
#   web_display       horizontal | vertical | interlinear
#   web_mono          true | false             (monospace reading face in the web UI)
#   web_versions      any of: bt, wuj, vul, grb, drb (comma list); empty = just default_version
#   pager             shell command, e.g. less -R; empty = off
#   use               calendar layers to stack over the universal calendar: names of
#                     ~/.config/lectio/calendars/<name>.ini files (comma list, order = precedence)
#
# [calendar] — computed-calendar placement options (defaults = Universal Roman Calendar):
#   epiphany          fixed | sunday    (fixed = Jan 6; sunday = the Sunday of Jan 2-8)
#   ascension         thursday | sunday (sunday = moved to the following Sunday, 7th of Easter)
#   corpus_christi    thursday | sunday (sunday = moved to the following Sunday)
#
# Optional [parts.new] / [parts.traditional] sections hide reading parts, e.g.:
#   [parts.new]
#   psalm = false
`

// Version is lectio's release version, shared by every binary's
// -v/--version output (lectio, lectio-ui, lectio-web).
const Version = "0.32.0"

// validVersions are the five scripture versions lectio understands.
var validVersions = map[string]bool{
	"bt":  true,
	"wuj": true,
	"vul": true,
	"grb": true,
	"drb": true,
}

// ValidVersion reports whether v is one of the five scripture versions
// lectio understands (bt, wuj, vul, grb, drb).
func ValidVersion(v string) bool {
	return validVersions[v]
}

// NormalizeLectionary maps -l/--lectionary's accepted spellings ("new",
// "trad", "traditional") onto the canonical Config.Lectionary values ("new",
// "traditional"); anything else reports ok=false.
func NormalizeLectionary(s string) (string, bool) {
	switch strings.ToLower(s) {
	case "new":
		return "new", true
	case "trad", "traditional":
		return "traditional", true
	default:
		return "", false
	}
}

// validDisplays are the lectio-web reading-pane layouts.
var validDisplays = map[string]bool{
	"horizontal":  true,
	"vertical":    true,
	"interlinear": true,
}

// NormalizeDisplay lower-cases display and falls back to "horizontal" when
// it is not one of validDisplays -- the same lenient style as the rest of
// lectio-web's config fields (no error, just a safe default). Exported so
// internal/web can apply the identical normalization to an explicit
// ?display= query override, keeping the valid set in this one place.
func NormalizeDisplay(display string) string {
	d := strings.ToLower(display)
	if !validDisplays[d] {
		return "horizontal"
	}
	return d
}

// validUILanguages are the two UI chrome languages lectio understands.
var validUILanguages = map[string]bool{
	"en": true,
	"pl": true,
}

// NormalizeUILanguage lower-cases lang and falls back to "en" when it is not
// one of validUILanguages -- the same lenient style as NormalizeDisplay (no
// error, just a safe default).
func NormalizeUILanguage(lang string) string {
	l := strings.ToLower(lang)
	if !validUILanguages[l] {
		return "en"
	}
	return l
}

// NormalizeSiglaStyle maps a sigla_style setting to one of "auto", "polish",
// "english"; anything unrecognised (incl. "") falls back to "auto". Accepts the
// short aliases "pl"/"en" for convenience.
func NormalizeSiglaStyle(s string) string {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "polish", "pl":
		return "polish"
	case "latin", "la":
		return "latin"
	case "english", "en":
		return "english"
	default:
		return "auto"
	}
}

// Config holds lectio's user-configurable settings. The toml tags are used only
// by the one-shot config.toml -> config.ini migration; the live format is INI.
type Config struct {
	SchemaVersion   int                        `toml:"schema_version"`
	Lectionary      string                     `toml:"lectionary"`
	TraditionalLang string                     `toml:"traditional_lang"`
	Versions        []string                   `toml:"versions"`
	DefaultVersion  string                     `toml:"default_version"`
	Width           int                        `toml:"width"`
	All             bool                       `toml:"all"`
	Offline         bool                       `toml:"offline"`
	UILanguage      string                     `toml:"ui_language"`
	SiglaStyle      string                     `toml:"sigla_style"`
	WebTheme        string                     `toml:"web_theme"`
	WebPort         int                        `toml:"web_port"`
	WebDisplay      string                     `toml:"web_display"`
	WebMono         bool                       `toml:"web_mono"`
	WebVersions     []string                   `toml:"web_versions"`
	Pager           string                     `toml:"pager"`
	Parts           map[string]map[string]bool `toml:"parts"`

	// Computed-calendar placement options (INI [calendar] section; INI-only).
	CalEpiphany      string `toml:"-"`
	CalAscension     string `toml:"-"`
	CalCorpusChristi string `toml:"-"`

	// Use is the ordered stack of user calendar-layer ids (INI "use"); each id
	// names a <CalendarsDir>/<id>.ini file layered over the universal calendar.
	Use []string `toml:"-"`
}

// PartShown reports whether a part renders: true unless explicitly set false.
func (c Config) PartShown(lectionary, partID string) bool {
	if m, ok := c.Parts[lectionary]; ok {
		if v, ok := m[partID]; ok {
			return v
		}
	}
	return true
}

// SiglaLang resolves the book dialect (a books.toml section code, "en"/"pl")
// that `lectio --ref`/`--list` use: the explicit sigla_style, or -- when "auto"
// -- the UI language.
func (c Config) SiglaLang() string {
	switch c.SiglaStyle {
	case "polish":
		return "pl"
	case "latin":
		return "la"
	case "english":
		return "en"
	default:
		if c.UILanguage == "pl" {
			return "pl"
		}
		return "en"
	}
}

// Selection maps the config onto the calendar engine's Selection: the form
// (from Lectionary: "new" -> OF, "traditional" -> EF) plus the national
// placement options, each falling back to the Universal Roman default.
func (c Config) Selection() calendar.Selection {
	sel := calendar.DefaultSelection()
	if c.Lectionary == "traditional" {
		sel.Form = "old"
	} else {
		sel.Form = "new"
	}
	if c.CalEpiphany != "" {
		sel.Epiphany = c.CalEpiphany
	}
	if c.CalAscension != "" {
		sel.Ascension = c.CalAscension
	}
	if c.CalCorpusChristi != "" {
		sel.CorpusChristi = c.CalCorpusChristi
	}
	return sel
}

// Default returns lectio's built-in configuration, used when no config file
// is found and as the base that a partial config file overrides.
func Default() Config {
	return Config{
		SchemaVersion:   1,
		Lectionary:      "new",
		TraditionalLang: "pl",
		Versions:        []string{"bt", "wuj", "vul", "grb", "drb"},
		DefaultVersion:  "bt",
		Width:           0,
		All:             false,
		Offline:         false,
		UILanguage:      "en",
		SiglaStyle:      "auto",
		WebTheme:        "transfiguration",
		WebPort:         0,
		WebDisplay:      "horizontal",
		WebMono:         false,
		WebVersions:     nil,
		Pager:           "",
		Parts:           nil,
	}
}

// configPath resolves the config file location: LECTIO_CONFIG if set,
// otherwise the default XDG-aware path under os.UserConfigDir(). The bool
// reports whether this is the default (seedable/migratable) location.
func configPath() (path string, isDefault bool, err error) {
	if p := os.Getenv("LECTIO_CONFIG"); p != "" {
		return p, false, nil
	}
	dir, err := os.UserConfigDir()
	if err != nil {
		return "", false, err
	}
	return filepath.Join(dir, "lectio", "config.ini"), true, nil
}

// CalendarsDir returns the directory holding user calendar-layer files
// (<config dir>/calendars).
func CalendarsDir() (string, error) {
	p, _, err := configPath()
	if err != nil {
		return "", err
	}
	return filepath.Join(filepath.Dir(p), "calendars"), nil
}

// BooksPath returns the path to the optional user books.ini (in the same
// directory as the config file). There is no embedded seed on disk -- absence
// means "use the built-in defaults".
func BooksPath() (string, error) {
	p, _, err := configPath()
	if err != nil {
		return "", err
	}
	return filepath.Join(filepath.Dir(p), "books.ini"), nil
}

// UserBooksINI returns the bytes of the optional user books.ini (see BooksPath),
// or nil when absent/unreadable -- callers then fall back to bible's embedded
// default table. A former books.toml at the same location is converted to
// books.ini once, on first read (the old file is kept).
func UserBooksINI() []byte {
	p, err := BooksPath()
	if err != nil {
		return nil
	}
	if b, err := os.ReadFile(p); err == nil {
		return b
	}
	tomlPath := filepath.Join(filepath.Dir(p), "books.toml")
	data, err := os.ReadFile(tomlPath)
	if err != nil {
		return nil
	}
	out := booksTOMLtoINI(data)
	if out == nil {
		return nil
	}
	_ = os.WriteFile(p, out, 0o644)
	fmt.Fprintf(os.Stderr, "lectio: migrated %s -> books.ini (old file kept)\n", tomlPath)
	return out
}

// booksTOMLtoINI converts a former books.toml (dialect -> book -> [forms]) into
// books.ini. Returns nil if the TOML is unparseable.
func booksTOMLtoINI(data []byte) []byte {
	var raw map[string]map[string][]string
	if err := toml.Unmarshal(data, &raw); err != nil {
		return nil
	}
	var b strings.Builder
	b.WriteString("# lectio book names & abbreviations, per dialect (migrated from books.toml).\n")
	emit := func(d string) {
		books := raw[d]
		if books == nil {
			return
		}
		fmt.Fprintf(&b, "\n[%s]\n", d)
		keys := make([]string, 0, len(books))
		for k := range books {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			fmt.Fprintf(&b, "%s = %s\n", k, strings.Join(books[k], ", "))
		}
	}
	seen := map[string]bool{"en": true, "pl": true, "la": true}
	emit("en")
	emit("pl")
	emit("la")
	others := make([]string, 0)
	for d := range raw {
		if !seen[d] {
			others = append(others, d)
		}
	}
	sort.Strings(others)
	for _, d := range others {
		emit(d)
	}
	return []byte(b.String())
}

// seedIfMissing writes the embedded default config to path if nothing is
// there yet.
func seedIfMissing(path string) error {
	if _, err := os.Stat(path); err == nil {
		return nil
	} else if !os.IsNotExist(err) {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	return os.WriteFile(path, renderConfigINI(Default()), 0o644)
}

// migrateFromTOML converts a former config.toml sitting next to iniPath into
// config.ini, once. The old file is left in place (so the change is
// reversible). A missing or unreadable config.toml is not an error.
func migrateFromTOML(iniPath string) {
	tomlPath := filepath.Join(filepath.Dir(iniPath), "config.toml")
	data, err := os.ReadFile(tomlPath)
	if err != nil {
		return
	}
	cfg := Default()
	if err := toml.Unmarshal(data, &cfg); err != nil {
		return
	}
	normalize(&cfg)
	_ = Save(cfg) // writes config.ini
	fmt.Fprintf(os.Stderr, "lectio: migrated %s -> config.ini (old file kept)\n", tomlPath)
}

// Load reads lectio's configuration, following the package's resolution order
// (see the package doc comment). It always returns a usable Config: on a
// missing config dir or an INI parse error it falls back to Default() (warning
// on stderr in the parse-error case). It returns a non-nil error only when the
// loaded config contains a semantically invalid value.
func Load() (Config, error) {
	def := Default()

	path, isDefault, err := configPath()
	if err != nil {
		fmt.Fprintf(os.Stderr, "lectio: warning: could not resolve config directory: %v; using defaults\n", err)
		return def, nil
	}

	if isDefault {
		if _, statErr := os.Stat(path); os.IsNotExist(statErr) {
			migrateFromTOML(path) // convert a former config.toml if present
			if err := seedIfMissing(path); err != nil {
				return def, err
			}
		}
	}

	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return def, nil
		}
		return def, err
	}

	cfg, err := readINI(data)
	if err != nil {
		fmt.Fprintf(os.Stderr, "lectio: warning: invalid config at %s: %v; using defaults\n", path, err)
		return def, nil
	}
	normalize(&cfg)

	if err := validate(cfg); err != nil {
		return Config{}, err
	}
	return cfg, nil
}

// normalize applies the lenient field fix-ups Load enforces after parsing.
func normalize(cfg *Config) {
	cfg.WebDisplay = NormalizeDisplay(cfg.WebDisplay)
	cfg.UILanguage = NormalizeUILanguage(cfg.UILanguage)
	cfg.SiglaStyle = NormalizeSiglaStyle(cfg.SiglaStyle)
}

// readINI parses INI bytes into a Config over Default(). Absent keys keep the
// default; present keys override (an empty list value clears the list).
func readINI(data []byte) (Config, error) {
	cfg := Default()
	secs, err := ini.Parse(data)
	if err != nil {
		return cfg, err
	}
	for _, s := range secs {
		switch {
		case s.Name == "":
			for _, p := range s.Pairs {
				applyScalar(&cfg, p.Key, p.Val)
			}
		case s.Name == "calendar":
			for _, p := range s.Pairs {
				switch p.Key {
				case "epiphany":
					cfg.CalEpiphany = p.Val
				case "ascension":
					cfg.CalAscension = p.Val
				case "corpus_christi":
					cfg.CalCorpusChristi = p.Val
				}
			}
		case strings.HasPrefix(s.Name, "parts."):
			lect := strings.TrimPrefix(s.Name, "parts.")
			if cfg.Parts == nil {
				cfg.Parts = map[string]map[string]bool{}
			}
			if cfg.Parts[lect] == nil {
				cfg.Parts[lect] = map[string]bool{}
			}
			for _, p := range s.Pairs {
				cfg.Parts[lect][p.Key] = p.Val == "true"
			}
		}
	}
	return cfg, nil
}

func applyScalar(cfg *Config, key, val string) {
	switch key {
	case "schema_version":
		cfg.SchemaVersion = atoiOr(val, cfg.SchemaVersion)
	case "lectionary":
		cfg.Lectionary = val
	case "traditional_lang":
		cfg.TraditionalLang = val
	case "versions":
		cfg.Versions = ini.List(val)
	case "default_version":
		cfg.DefaultVersion = val
	case "width":
		cfg.Width = atoiOr(val, cfg.Width)
	case "all":
		cfg.All = val == "true"
	case "offline":
		cfg.Offline = val == "true"
	case "ui_language":
		cfg.UILanguage = val
	case "sigla_style":
		cfg.SiglaStyle = val
	case "web_theme":
		cfg.WebTheme = val
	case "web_port":
		cfg.WebPort = atoiOr(val, cfg.WebPort)
	case "web_display":
		cfg.WebDisplay = val
	case "web_mono":
		cfg.WebMono = val == "true"
	case "web_versions":
		cfg.WebVersions = ini.List(val)
	case "pager":
		cfg.Pager = val
	case "use":
		cfg.Use = ini.List(val)
	}
}

func atoiOr(s string, def int) int {
	if n, err := strconv.Atoi(strings.TrimSpace(s)); err == nil {
		return n
	}
	return def
}

// validate checks the semantic constraints Load enforces beyond parsing.
func validate(cfg Config) error {
	if cfg.Lectionary != "new" && cfg.Lectionary != "traditional" {
		return fmt.Errorf("config: invalid lectionary %q (must be \"new\" or \"traditional\")", cfg.Lectionary)
	}
	if cfg.TraditionalLang != "pl" && cfg.TraditionalLang != "en" {
		return fmt.Errorf("config: invalid traditional_lang %q (must be \"pl\" or \"en\")", cfg.TraditionalLang)
	}
	for _, v := range cfg.Versions {
		if !validVersions[v] {
			return fmt.Errorf("config: invalid version %q in versions (must be one of bt, wuj, vul, grb, drb)", v)
		}
	}
	if !validVersions[cfg.DefaultVersion] {
		return fmt.Errorf("config: invalid default_version %q (must be one of bt, wuj, vul, grb, drb)", cfg.DefaultVersion)
	}
	for _, v := range cfg.WebVersions {
		if !validVersions[v] {
			return fmt.Errorf("config: invalid version %q in web_versions (must be one of bt, wuj, vul, grb, drb)", v)
		}
	}
	return nil
}

// Validate exposes the semantic checks Load applies, so callers that build a
// Config (the web /settings form) can reject an invalid one before saving.
func Validate(cfg Config) error { return validate(cfg) }

// Save writes cfg to the config file (configPath, honoring LECTIO_CONFIG),
// creating the directory if needed, as commented INI.
func Save(cfg Config) error {
	path, _, err := configPath()
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	return os.WriteFile(path, renderConfigINI(cfg), 0o644)
}

// renderConfigINI regenerates config.ini from cfg. Comments are on their own
// lines so no value ever shares a line with a "#"/";" comment character.
func renderConfigINI(cfg Config) []byte {
	var b strings.Builder
	b.WriteString(configHeader)
	b.WriteString("\n")
	fmt.Fprintf(&b, "schema_version = %d\n", cfg.SchemaVersion)
	fmt.Fprintf(&b, "lectionary = %s\n", cfg.Lectionary)
	fmt.Fprintf(&b, "traditional_lang = %s\n", cfg.TraditionalLang)
	fmt.Fprintf(&b, "versions = %s\n", strings.Join(cfg.Versions, ", "))
	fmt.Fprintf(&b, "default_version = %s\n", cfg.DefaultVersion)
	fmt.Fprintf(&b, "width = %d\n", cfg.Width)
	fmt.Fprintf(&b, "all = %t\n", cfg.All)
	fmt.Fprintf(&b, "offline = %t\n", cfg.Offline)
	fmt.Fprintf(&b, "ui_language = %s\n", cfg.UILanguage)
	fmt.Fprintf(&b, "sigla_style = %s\n", cfg.SiglaStyle)
	fmt.Fprintf(&b, "web_theme = %s\n", cfg.WebTheme)
	fmt.Fprintf(&b, "web_port = %d\n", cfg.WebPort)
	fmt.Fprintf(&b, "web_display = %s\n", cfg.WebDisplay)
	fmt.Fprintf(&b, "web_mono = %t\n", cfg.WebMono)
	fmt.Fprintf(&b, "web_versions = %s\n", strings.Join(cfg.WebVersions, ", "))
	fmt.Fprintf(&b, "pager = %s\n", cfg.Pager)
	fmt.Fprintf(&b, "use = %s\n", strings.Join(cfg.Use, ", "))

	b.WriteString("\n# Computed-calendar national placement options.\n[calendar]\n")
	fmt.Fprintf(&b, "epiphany = %s\n", orDefault(cfg.CalEpiphany, "fixed"))
	fmt.Fprintf(&b, "ascension = %s\n", orDefault(cfg.CalAscension, "thursday"))
	fmt.Fprintf(&b, "corpus_christi = %s\n", orDefault(cfg.CalCorpusChristi, "thursday"))

	// Preserve the parts map (per-lectionary hide flags) across a Save.
	lects := make([]string, 0, len(cfg.Parts))
	for l := range cfg.Parts {
		lects = append(lects, l)
	}
	sort.Strings(lects)
	for _, l := range lects {
		parts := cfg.Parts[l]
		keys := make([]string, 0, len(parts))
		for k := range parts {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		fmt.Fprintf(&b, "\n[parts.%s]\n", l)
		for _, k := range keys {
			fmt.Fprintf(&b, "%s = %t\n", k, parts[k])
		}
	}
	return []byte(b.String())
}

func orDefault(v, def string) string {
	if v == "" {
		return def
	}
	return v
}