// Pure layout/formatting logic for the clock bar.
//
// Deliberately free of QML types so it can be unit-tested under node (see
// tests/model.test.js). The QML side owns IO — reading config, probing tzdata,
// ticking the clock — and hands the results in here as plain values.
//
// Everything is driven by UTC offsets rather than by conversion, because Qt's
// QML engine has no `Intl`, so there is no way to render an IANA zone from
// inside QML. Offsets come from `date +%z` against the system tzdata, which
// makes them DST-correct for the moment they were probed; the bar re-probes
// often enough that a transition is picked up within minutes.

var MINUTES = 60 * 1000

// "+0200" / "-0730" / "+02" -> minutes east of UTC. null when unparseable, so
// a zone that tzdata did not recognise can be shown as broken rather than
// silently rendered as UTC.
function parseOffset(raw) {
  var s = String(raw === undefined || raw === null ? "" : raw).replace(/^\s+|\s+$/g, "")
  var m = s.match(/^([+-])(\d{2}):?(\d{2})?$/)
  if (!m) return null
  var sign = m[1] === "-" ? -1 : 1
  var hours = parseInt(m[2], 10)
  var mins = m[3] ? parseInt(m[3], 10) : 0
  if (!isFinite(hours) || !isFinite(mins) || mins > 59) return null
  return sign * (hours * 60 + mins)
}

// The wall clock in a zone, expressed as a Date whose *UTC* fields carry that
// zone's local time. Reading it back with getUTC* keeps the arithmetic in one
// frame of reference no matter what the host machine's own zone is.
function wallClock(utcMs, offsetMinutes) {
  return new Date(utcMs + offsetMinutes * MINUTES)
}

function pad2(n) {
  return (n < 10 ? "0" : "") + n
}

function formatTime(wall, withSeconds) {
  var out = pad2(wall.getUTCHours()) + ":" + pad2(wall.getUTCMinutes())
  return withSeconds ? out + ":" + pad2(wall.getUTCSeconds()) : out
}

// Whole-day difference between two wall clocks, from their calendar dates
// alone. Comparing the dates rather than subtracting the times means a clock
// 30 minutes and one day apart still reports exactly 1.
function dayDelta(wall, localWall) {
  var a = Date.UTC(wall.getUTCFullYear(), wall.getUTCMonth(), wall.getUTCDate())
  var b = Date.UTC(localWall.getUTCFullYear(), localWall.getUTCMonth(), localWall.getUTCDate())
  return Math.round((a - b) / (24 * 60 * MINUTES))
}

// "+1" / "-1" / "" — shown to the right of the time. Anything beyond a single
// day is still rendered honestly (no real zone pair reaches it, but a bad
// hand-edited offset should not silently truncate).
function dayMarker(delta) {
  if (!delta) return ""
  return (delta > 0 ? "+" : "-") + Math.abs(delta)
}

function normalizeWorkdays(raw) {
  if (!raw || !raw.length) return [1, 2, 3, 4, 5]
  var out = []
  for (var i = 0; i < raw.length; i++) {
    var n = Number(raw[i])
    if (isFinite(n) && n >= 0 && n <= 6 && out.indexOf(n) === -1) out.push(n)
  }
  return out.length ? out : [1, 2, 3, 4, 5]
}

// Working hours are evaluated in the clock's *own* zone — the question the bar
// answers is "is this person around?", not "is this hour within my day?".
// A window that wraps midnight (22 -> 6) is treated as spanning the boundary.
function isWorkingHours(wall, hours) {
  var start = hours && isFinite(Number(hours.start)) ? Number(hours.start) : 8
  var end = hours && isFinite(Number(hours.end)) ? Number(hours.end) : 18
  var days = normalizeWorkdays(hours && hours.workdays)
  if (days.indexOf(wall.getUTCDay()) === -1) return false

  var hour = wall.getUTCHours() + wall.getUTCMinutes() / 60
  if (start === end) return true
  if (start < end) return hour >= start && hour < end
  return hour >= start || hour < end
}

function isValidLabel(label) {
  return typeof label === "string" && label.replace(/^\s+|\s+$/g, "").length > 0
}

// One rendered clock. `offsets` maps zone -> "+0200" as probed from tzdata;
// a zone missing from it (or unparseable) yields `known: false` so the bar can
// show the label struck through instead of quietly lying about the time.
function buildClock(entry, offsets, utcMs, localOffset, options) {
  var opts = options || {}
  var timezone = String(entry && entry.timezone ? entry.timezone : "")
  var label = isValidLabel(entry && entry.label) ? String(entry.label).replace(/^\s+|\s+$/g, "") : timezone
  var offset = parseOffset(offsets ? offsets[timezone] : null)

  if (offset === null) {
    return {
      label: label, timezone: timezone, known: false,
      time: "--:--", marker: "", delta: 0, relativeMinutes: 0, working: false
    }
  }

  var wall = wallClock(utcMs, offset)
  var localWall = wallClock(utcMs, localOffset)
  var delta = dayDelta(wall, localWall)

  return {
    label: label,
    timezone: timezone,
    known: true,
    time: formatTime(wall, opts.showSeconds === true),
    marker: dayMarker(delta),
    delta: delta,
    relativeMinutes: offset - localOffset,
    working: isWorkingHours(wall, opts.workingHours)
  }
}

// Sort key: how far ahead of (or behind) local this clock is. Equal offsets
// tie-break on label so the bar does not reshuffle between ticks.
function compareClocks(a, b) {
  if (a.relativeMinutes !== b.relativeMinutes) return a.relativeMinutes - b.relativeMinutes
  return a.label < b.label ? -1 : (a.label > b.label ? 1 : 0)
}

// The whole bar: one continuous timeline with local time at its centre.
// Behind-local runs out to the left, ahead-of-local out to the right, each
// group ordered so that reading left to right always moves forward in time.
// Side and position fall out of the live offset, so a DST shift re-sorts the
// bar on the next probe with no config change.
function buildBar(config, offsets, utcMs, localOffsetRaw) {
  var cfg = config || {}
  var localOffset = parseOffset(localOffsetRaw)
  if (localOffset === null) localOffset = 0

  var options = {
    workingHours: cfg.workingHours,
    showSeconds: cfg.showSeconds === true
  }

  var entries = Array.isArray(cfg.clocks) ? cfg.clocks : []
  var left = []
  var right = []
  var unknown = []

  for (var i = 0; i < entries.length; i++) {
    var clock = buildClock(entries[i], offsets, utcMs, localOffset, options)
    if (!clock.known) unknown.push(clock)
    else if (clock.relativeMinutes < 0) left.push(clock)
    else right.push(clock)
  }

  left.sort(compareClocks)
  right.sort(compareClocks)

  var localWall = wallClock(utcMs, localOffset)

  return {
    left: left,
    // Unresolvable zones have no place on a timeline, so they sit at the end
    // of the trailing group where they are visible but never mis-ordered.
    right: right.concat(unknown),
    center: {
      time: formatTime(localWall, options.showSeconds),
      date: localWall.getUTCFullYear() + "-" + pad2(localWall.getUTCMonth() + 1) + "-" + pad2(localWall.getUTCDate()),
      offsetMinutes: localOffset
    }
  }
}

// Every zone the bar needs an offset for, deduplicated, for the probe command.
function zonesToProbe(config) {
  var entries = config && Array.isArray(config.clocks) ? config.clocks : []
  var seen = {}
  var out = []
  for (var i = 0; i < entries.length; i++) {
    var tz = entries[i] && entries[i].timezone ? String(entries[i].timezone) : ""
    // Zone names reach a shell command, so anything outside the tzdata naming
    // shape is dropped here rather than quoted and hoped for.
    if (!tz || !/^[A-Za-z0-9_+\-]+(\/[A-Za-z0-9_+\-]+)*$/.test(tz)) continue
    if (seen[tz]) continue
    seen[tz] = true
    out.push(tz)
  }
  return out
}

// Parse the probe's "zone<TAB>+0200" lines back into a lookup.
function parseOffsetReport(raw) {
  var out = {}
  var lines = String(raw || "").split("\n")
  for (var i = 0; i < lines.length; i++) {
    var line = lines[i].replace(/^\s+|\s+$/g, "")
    if (!line) continue
    var tab = line.indexOf("\t")
    if (tab <= 0) continue
    out[line.substring(0, tab)] = line.substring(tab + 1).replace(/^\s+|\s+$/g, "")
  }
  return out
}

if (typeof module !== "undefined" && module.exports) {
  module.exports = {
    parseOffset: parseOffset,
    wallClock: wallClock,
    formatTime: formatTime,
    dayDelta: dayDelta,
    dayMarker: dayMarker,
    isWorkingHours: isWorkingHours,
    buildClock: buildClock,
    buildBar: buildBar,
    zonesToProbe: zonesToProbe,
    parseOffsetReport: parseOffsetReport
  }
}