const Range = require('../classes/range.js')
const { ANY } = require('../classes/comparator.js')
const satisfies = require('../functions/satisfies.js')
const compare = require('../functions/compare.js')

// Complex range `r1 || r2 || ...` is a subset of `R1 || R2 || ...` iff:
// - Every simple range `r1, r2, ...` is a subset of some `R1, R2, ...`
//
// Simple range `c1 c2 ...` is a subset of simple range `C1 C2 ...` iff:
// - If c is only the ANY comparator
//   - If C is only the ANY comparator, return true
//   - Else return false
// - Let EQ be the set of = comparators in c
// - If EQ is more than one, return true (null set)
// - Let GT be the highest > or >= comparator in c
// - Let LT be the lowest < or <= comparator in c
// - If GT and LT, and GT.semver > LT.semver, return true (null set)
// - If EQ
//   - If GT, and EQ does not satisfy GT, return true (null set)
//   - If LT, and EQ does not satisfy LT, return true (null set)
//   - If EQ satisfies every C, return true
//   - Else return false
// - If GT
//   - If GT.semver is lower than any > or >= comp in C, return false
//   - If GT is >=, and GT.semver does not satisfy every C, return false
// - If LT
//   - If LT.semver is greater than any < or <= comp in C, return false
//   - If LT is <=, and LT.semver does not satisfy every C, return false
// - If any C is a = range, and GT or LT are set, return false
// - Else return true

const subset = (sub, dom, options) => {
  if (sub === dom)
    return true

  sub = new Range(sub, options)
  dom = new Range(dom, options)
  let sawNonNull = false

  OUTER: for (const simpleSub of sub.set) {
    for (const simpleDom of dom.set) {
      const isSub = simpleSubset(simpleSub, simpleDom, options)
      sawNonNull = sawNonNull || isSub !== null
      if (isSub)
        continue OUTER
    }
    // the null set is a subset of everything, but null simple ranges in
    // a complex range should be ignored.  so if we saw a non-null range,
    // then we know this isn't a subset, but if EVERY simple range was null,
    // then it is a subset.
    if (sawNonNull)
      return false
  }
  return true
}

const simpleSubset = (sub, dom, options) => {
  if (sub === dom)
    return true

  if (sub.length === 1 && sub[0].semver === ANY)
    return dom.length === 1 && dom[0].semver === ANY

  const eqSet = new Set()
  let gt, lt
  for (const c of sub) {
    if (c.operator === '>' || c.operator === '>=')
      gt = higherGT(gt, c, options)
    else if (c.operator === '<' || c.operator === '<=')
      lt = lowerLT(lt, c, options)
    else
      eqSet.add(c.semver)
  }

  if (eqSet.size > 1)
    return null

  let gtltComp
  if (gt && lt) {
    gtltComp = compare(gt.semver, lt.semver, options)
    if (gtltComp > 0)
      return null
    else if (gtltComp === 0 && (gt.operator !== '>=' || lt.operator !== '<='))
      return null
  }

  // will iterate one or zero times
  for (const eq of eqSet) {
    if (gt && !satisfies(eq, String(gt), options))
      return null

    if (lt && !satisfies(eq, String(lt), options))
      return null

    for (const c of dom) {
      if (!satisfies(eq, String(c), options))
        return false
    }

    return true
  }

  let higher, lower
  let hasDomLT, hasDomGT
  for (const c of dom) {
    hasDomGT = hasDomGT || c.operator === '>' || c.operator === '>='
    hasDomLT = hasDomLT || c.operator === '<' || c.operator === '<='
    if (gt) {
      if (c.operator === '>' || c.operator === '>=') {
        higher = higherGT(gt, c, options)
        if (higher === c && higher !== gt)
          return false
      } else if (gt.operator === '>=' && !satisfies(gt.semver, String(c), options))
        return false
    }
    if (lt) {
      if (c.operator === '<' || c.operator === '<=') {
        lower = lowerLT(lt, c, options)
        if (lower === c && lower !== lt)
          return false
      } else if (lt.operator === '<=' && !satisfies(lt.semver, String(c), options))
        return false
    }
    if (!c.operator && (lt || gt) && gtltComp !== 0)
      return false
  }

  // if there was a < or >, and nothing in the dom, then must be false
  // UNLESS it was limited by another range in the other direction.
  // Eg, >1.0.0 <1.0.1 is still a subset of <2.0.0
  if (gt && hasDomLT && !lt && gtltComp !== 0)
    return false

  if (lt && hasDomGT && !gt && gtltComp !== 0)
    return false

  return true
}

// >=1.2.3 is lower than >1.2.3
const higherGT = (a, b, options) => {
  if (!a)
    return b
  const comp = compare(a.semver, b.semver, options)
  return comp > 0 ? a
    : comp < 0 ? b
    : b.operator === '>' && a.operator === '>=' ? b
    : a
}

// <=1.2.3 is higher than <1.2.3
const lowerLT = (a, b, options) => {
  if (!a)
    return b
  const comp = compare(a.semver, b.semver, options)
  return comp < 0 ? a
    : comp > 0 ? b
    : b.operator === '<' && a.operator === '<=' ? b
    : a
}

module.exports = subset