// Pure JS logic for the thesinging.bible player. No QML in here so it can be
// reasoned about (and, if ever needed, unit tested) independently of the
// widget wiring in BarWidget.qml.
//
// Data model, mirrored from https://thesinging.bible/manifest.json:
//   translations[], voices[], ages[], styles[]  -- each {id, name, enabled}
//   books[]                                     -- {num, slug, name, section, chapters}
//   availability["t/v/a/s"]["NN-slug"] -> [chapter numbers available]
//
// Only ~32 of the possible translation x voice x age x style combos are
// actually populated (source: manifest fetched 2026-09-15). The UI lets a
// listener pick any style/voice/language regardless, so every selection
// change is routed through resolveSelection() below to land on a real combo
// (falling back to child voice-age, then to the first available book/chapter
// for that style, then to "nothing available") rather than assuming the
// picked combo has audio.

function bookKey(book) {
  return String(book.num).padStart(2, "0") + "-" + book.slug
}

function findBook(manifest, key) {
  if (!manifest || !manifest.books) return null
  for (var i = 0; i < manifest.books.length; i++) {
    if (bookKey(manifest.books[i]) === key) return manifest.books[i]
  }
  return null
}

function comboKey(t, v, a, s) {
  return t + "/" + v + "/" + a + "/" + s
}

function chaptersFor(manifest, t, v, a, s, bookKeyStr) {
  var combo = manifest && manifest.availability ? manifest.availability[comboKey(t, v, a, s)] : null
  if (!combo) return []
  var chapters = combo[bookKeyStr]
  return chapters ? chapters : []
}

function parseManifest(raw) {
  try {
    var data = JSON.parse(String(raw || ""))
    if (!data || !data.translations || !data.voices || !data.styles || !data.books || !data.availability) return null
    return data
  } catch (e) {
    return null
  }
}

function enabledFirst(list) {
  if (!list) return null
  for (var i = 0; i < list.length; i++) {
    if (list[i] && list[i].enabled !== false) return list[i]
  }
  return list.length ? list[0] : null
}

// Language is hard-coded to English (sbe) — no Language dropdown, no
// per-user Spanish selection.
var FIXED_TRANSLATION = "sbe"

function defaultDesired(manifest) {
  var v = enabledFirst(manifest.voices)
  var s = enabledFirst(manifest.styles)
  return {
    translation: FIXED_TRANSLATION,
    voice: v ? v.id : "",
    style: s ? s.id : "",
    book: manifest.books && manifest.books.length ? bookKey(manifest.books[0]) : "01-genesis",
    chapter: 1
  }
}

// Age isn't a user-facing control (mirrors the real site): try adult first,
// fall back to child, for the exact book+chapter requested.
function resolveAge(manifest, t, v, s, bookKeyStr, chapter) {
  if (chaptersFor(manifest, t, v, "adult", s, bookKeyStr).indexOf(chapter) !== -1) return "adult"
  if (chaptersFor(manifest, t, v, "child", s, bookKeyStr).indexOf(chapter) !== -1) return "child"
  return null
}

// First book (in manifest order) with any content at all for this
// translation/voice/style, trying adult before child. Used when the exact
// requested book has nothing for the new combo.
function firstAvailableBookAndChapter(manifest, t, v, s) {
  var ages = ["adult", "child"]
  for (var a = 0; a < ages.length; a++) {
    var combo = manifest.availability[comboKey(t, v, ages[a], s)]
    if (!combo) continue
    for (var i = 0; i < manifest.books.length; i++) {
      var key = bookKey(manifest.books[i])
      var chapters = combo[key]
      if (chapters && chapters.length) return { age: ages[a], book: key, chapter: chapters[0] }
    }
  }
  return null
}

// Takes a desired {translation, voice, style, book, chapter} and returns a
// fully valid {translation, voice, style, age, book, chapter}, or null if
// this translation/voice/style has no audio at all. Never throws.
function resolveSelection(manifest, desired) {
  if (!manifest || !desired) return null
  var t = desired.translation, v = desired.voice, s = desired.style
  var book = desired.book, chapter = desired.chapter

  var age = resolveAge(manifest, t, v, s, book, chapter)
  if (age) return { translation: t, voice: v, style: s, age: age, book: book, chapter: chapter }

  var ages = ["adult", "child"]
  for (var a = 0; a < ages.length; a++) {
    var combo = manifest.availability[comboKey(t, v, ages[a], s)]
    if (combo && combo[book] && combo[book].length) {
      return { translation: t, voice: v, style: s, age: ages[a], book: book, chapter: combo[book][0] }
    }
  }

  var fb = firstAvailableBookAndChapter(manifest, t, v, s)
  if (fb) return { translation: t, voice: v, style: s, age: fb.age, book: fb.book, chapter: fb.chapter }

  return null
}

function audioUrl(baseUrl, sel) {
  return baseUrl.replace(/\/$/, "") + "/" + sel.translation + "/" + sel.voice + "/" + sel.age + "/" + sel.style +
    "/" + sel.book + "/" + String(sel.chapter).padStart(3, "0") + ".mp3"
}

function trackLabel(manifest, sel) {
  var book = findBook(manifest, sel.book)
  return (book ? book.name : sel.book) + " " + sel.chapter
}

// direction: +1 (next) or -1 (prev). Walks chapters within the current book
// first, then wraps to the next/previous book (in manifest order) that has
// any content for the current combo.
function neighborChapter(manifest, sel, direction) {
  var combo = manifest.availability[comboKey(sel.translation, sel.voice, sel.age, sel.style)]
  var chapters = combo && combo[sel.book] ? combo[sel.book] : []
  var idx = chapters.indexOf(sel.chapter)
  if (idx === -1) idx = 0
  var nextIdx = idx + direction

  if (nextIdx >= 0 && nextIdx < chapters.length) {
    return { translation: sel.translation, voice: sel.voice, style: sel.style, age: sel.age, book: sel.book, chapter: chapters[nextIdx] }
  }

  var bIdx = -1
  for (var i = 0; i < manifest.books.length; i++) {
    if (bookKey(manifest.books[i]) === sel.book) { bIdx = i; break }
  }
  if (bIdx === -1) return sel

  var n = manifest.books.length
  for (var step = 1; step <= n; step++) {
    var candidateIdx = ((bIdx + direction * step) % n + n) % n
    var candidateKey = bookKey(manifest.books[candidateIdx])
    var resolved = resolveSelection(manifest, {
      translation: sel.translation, voice: sel.voice, style: sel.style,
      book: candidateKey, chapter: direction > 0 ? 1 : 1
    })
    if (resolved && resolved.book === candidateKey) {
      if (direction < 0) {
        var combo2 = manifest.availability[comboKey(resolved.translation, resolved.voice, resolved.age, resolved.style)]
        var chs = combo2 && combo2[resolved.book] ? combo2[resolved.book] : []
        if (chs.length) resolved.chapter = chs[chs.length - 1]
      }
      return resolved
    }
  }
  return sel
}

function randomSelection(manifest, sel) {
  var candidates = []
  var ages = ["adult", "child"]
  for (var a = 0; a < ages.length; a++) {
    var combo = manifest.availability[comboKey(sel.translation, sel.voice, ages[a], sel.style)]
    if (!combo) continue
    for (var key in combo) {
      var chapters = combo[key]
      for (var i = 0; i < chapters.length; i++) candidates.push({ age: ages[a], book: key, chapter: chapters[i] })
    }
  }
  if (!candidates.length) return sel
  var pick = candidates[Math.floor(Math.random() * candidates.length)]
  return { translation: sel.translation, voice: sel.voice, style: sel.style, age: pick.age, book: pick.book, chapter: pick.chapter }
}

function toOptions(list) {
  var out = []
  if (!list) return out
  for (var i = 0; i < list.length; i++) {
    if (list[i].enabled === false) continue
    out.push({ value: list[i].id, label: list[i].name })
  }
  return out
}

function optionsForBooks(manifest) {
  var out = []
  for (var i = 0; i < manifest.books.length; i++) {
    out.push({ value: bookKey(manifest.books[i]), label: manifest.books[i].name })
  }
  return out
}

// Alabanza only has Spanish recordings (no sbe/*/alabanza in availability),
// so it's excluded here to avoid a style that silently plays nothing.
function optionsForStyles(manifest) {
  return toOptions(manifest.styles).filter(function(o) { return o.value !== "alabanza" })
}
function optionsForVoices(manifest) { return toOptions(manifest.voices) }
function optionsForChapters(manifest, sel) {
  var chapters = chaptersFor(manifest, sel.translation, sel.voice, sel.age, sel.style, sel.book)
  var out = []
  for (var i = 0; i < chapters.length; i++) out.push({ value: String(chapters[i]), label: String(chapters[i]) })
  return out
}

function parseStateFile(raw) {
  try {
    var data = JSON.parse(String(raw || ""))
    if (!data || typeof data !== "object") return null
    if (!data.voice || !data.style || !data.book || !data.chapter) return null
    return {
      // Forced regardless of what an older state.json saved (from before
      // Language was hard-coded to English).
      translation: FIXED_TRANSLATION,
      voice: String(data.voice),
      style: String(data.style),
      book: String(data.book),
      chapter: parseInt(data.chapter, 10) || 1
    }
  } catch (e) {
    return null
  }
}

function serializeState(sel) {
  return JSON.stringify({
    translation: sel.translation, voice: sel.voice, style: sel.style, book: sel.book, chapter: sel.chapter
  })
}

function formatTime(sec) {
  var s = Math.max(0, Math.floor(sec || 0))
  var m = Math.floor(s / 60)
  var r = s % 60
  return m + ":" + (r < 10 ? "0" + r : String(r))
}