const Range = require('../classes/range.js');
const Comparator = require('../classes/comparator.js');
const { ANY } = Comparator;
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 null set, OR
// - Every simple range `r1, r2, ...` which is not a null set 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 if in prerelease mode, return false
//   - else replace c with `[>=0.0.0]`
// - If C is only the ANY comparator
//   - if in prerelease mode, return true
//   - else replace C with `[>=0.0.0]`
// - 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 any C is a = range, and GT or LT are set, return false
// - 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 GT.semver has a prerelease, and not in prerelease mode
//     - If no C has a prerelease and the GT.semver tuple, 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 GT.semver has a prerelease, and not in prerelease mode
//     - If no C has a prerelease and the LT.semver tuple, 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 minimumVersionWithPreRelease = [new Comparator('>=0.0.0-0')];
const minimumVersion = [new Comparator('>=0.0.0')];

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

  if (sub.length === 1 && sub[0].semver === ANY) {
    if (dom.length === 1 && dom[0].semver === ANY) {
      return true;
    } else if (options.includePrerelease) {
      sub = minimumVersionWithPreRelease;
    } else {
      sub = minimumVersion;
    }
  }

  if (dom.length === 1 && dom[0].semver === ANY) {
    if (options.includePrerelease) {
      return true;
    } else {
      dom = minimumVersion;
    }
  }

  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;
  // if the subset has a prerelease, we need a comparator in the superset
  // with the same tuple and a prerelease, or it's not a subset
  let needDomLTPre =
    lt && !options.includePrerelease && lt.semver.prerelease.length ?
      lt.semver
    : false;
  let needDomGTPre =
    gt && !options.includePrerelease && gt.semver.prerelease.length ?
      gt.semver
    : false;
  // exception: <1.2.3-0 is the same as <1.2.3
  if (
    needDomLTPre &&
    needDomLTPre.prerelease.length === 1 &&
    lt.operator === '<' &&
    needDomLTPre.prerelease[0] === 0
  ) {
    needDomLTPre = false;
  }

  for (const c of dom) {
    hasDomGT = hasDomGT || c.operator === '>' || c.operator === '>=';
    hasDomLT = hasDomLT || c.operator === '<' || c.operator === '<=';
    if (gt) {
      if (needDomGTPre) {
        if (
          c.semver.prerelease &&
          c.semver.prerelease.length &&
          c.semver.major === needDomGTPre.major &&
          c.semver.minor === needDomGTPre.minor &&
          c.semver.patch === needDomGTPre.patch
        ) {
          needDomGTPre = false;
        }
      }
      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 (needDomLTPre) {
        if (
          c.semver.prerelease &&
          c.semver.prerelease.length &&
          c.semver.major === needDomLTPre.major &&
          c.semver.minor === needDomLTPre.minor &&
          c.semver.patch === needDomLTPre.patch
        ) {
          needDomLTPre = false;
        }
      }
      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;
  }

  // we needed a prerelease range in a specific tuple, but didn't get one
  // then this isn't a subset.  eg >=1.2.3-pre is not a subset of >=1.0.0,
  // because it includes prereleases in the 1.2.3 tuple
  if (needDomGTPre || needDomLTPre) {
    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;