export type ReviewSamplingBucket = "latest" | "hot" | "negative";

export interface ReviewSamplingComment {
  id: string;
  content: string;
  score: string | null;
  createdAt: string | null;
  authorLabel: string | null;
}

export interface SampledReviewComment<T extends ReviewSamplingComment = ReviewSamplingComment> {
  bucket: ReviewSamplingBucket;
  comment: T;
}

export interface ReviewSamplingResult<T extends ReviewSamplingComment = ReviewSamplingComment> {
  targetCount: number;
  actualCount: number;
  sampleInsufficient: boolean;
  bucketCounts: Record<ReviewSamplingBucket, number>;
  comments: Array<SampledReviewComment<T>>;
}

const BUCKET_WEIGHTS: Record<ReviewSamplingBucket, number> = {
  latest: 0.4,
  hot: 0.3,
  negative: 0.3
};

const QUOTA_PRIORITY: ReviewSamplingBucket[] = ["latest", "hot", "negative"];
const SELECTION_PRIORITY: ReviewSamplingBucket[] = ["negative", "hot", "latest"];
const FALLBACK_PRIORITY: ReviewSamplingBucket[] = ["latest", "hot", "negative"];

function normalizeBudget(value: number): number {
  if (!Number.isFinite(value) || value <= 0) {
    return 0;
  }

  return Math.floor(value);
}

function parseScore(score: string | null): number | null {
  if (!score) {
    return null;
  }

  const parsed = Number.parseInt(score, 10);
  return Number.isNaN(parsed) ? null : parsed;
}

function isNegativeComment(
  comment: ReviewSamplingComment,
  negativeKeywords: string[]
): boolean {
  const score = parseScore(comment.score);
  if (score !== null && score <= 3) {
    return true;
  }

  const normalizedContent = comment.content.toLowerCase();
  return negativeKeywords.some((keyword) => normalizedContent.includes(keyword.toLowerCase()));
}

function getHotScore(comment: ReviewSamplingComment): number {
  const score = parseScore(comment.score);
  const scoreBonus = score !== null && score >= 4 ? 16 : score === 3 ? 8 : 0;
  const authorBonus = comment.authorLabel ? 12 : 0;
  const timestampBonus = comment.createdAt ? 4 : 0;

  return Math.min(comment.content.length, 160) + scoreBonus + authorBonus + timestampBonus;
}

function dedupeComments<T extends ReviewSamplingComment>(comments: T[]): T[] {
  const deduped = new Map<string, T>();
  for (const comment of comments) {
    if (!deduped.has(comment.id)) {
      deduped.set(comment.id, comment);
    }
  }

  return Array.from(deduped.values());
}

function buildBucketTargets(
  targetCount: number,
  availability: Record<ReviewSamplingBucket, boolean>
): Record<ReviewSamplingBucket, number> {
  const normalizedTarget = normalizeBudget(targetCount);
  const activeBuckets = QUOTA_PRIORITY.filter((bucket) => availability[bucket]);
  const targets: Record<ReviewSamplingBucket, number> = {
    latest: 0,
    hot: 0,
    negative: 0
  };

  if (normalizedTarget === 0 || activeBuckets.length === 0) {
    return targets;
  }

  const activeWeight = activeBuckets.reduce((sum, bucket) => sum + BUCKET_WEIGHTS[bucket], 0);
  let allocated = 0;
  const fractions = activeBuckets.map((bucket) => {
    const raw = (normalizedTarget * BUCKET_WEIGHTS[bucket]) / activeWeight;
    const base = Math.floor(raw);
    targets[bucket] = base;
    allocated += base;

    return {
      bucket,
      fraction: raw - base
    };
  });

  let remainder = normalizedTarget - allocated;
  fractions
    .sort(
      (left, right) =>
        right.fraction - left.fraction ||
        QUOTA_PRIORITY.indexOf(left.bucket) - QUOTA_PRIORITY.indexOf(right.bucket)
    )
    .forEach(({ bucket }) => {
      if (remainder <= 0) {
        return;
      }

      targets[bucket] += 1;
      remainder -= 1;
    });

  return targets;
}

function hasUnusedComment<T extends ReviewSamplingComment>(pool: T[], usedIds: Set<string>): boolean {
  return pool.some((comment) => !usedIds.has(comment.id));
}

function pickNextComment<T extends ReviewSamplingComment>(
  bucket: ReviewSamplingBucket,
  pool: T[],
  usedIds: Set<string>,
  selected: Array<SampledReviewComment<T>>,
  bucketCounts: Record<ReviewSamplingBucket, number>
): boolean {
  for (const comment of pool) {
    if (usedIds.has(comment.id)) {
      continue;
    }

    usedIds.add(comment.id);
    selected.push({
      bucket,
      comment
    });
    bucketCounts[bucket] += 1;
    return true;
  }

  return false;
}

export function buildReviewBudgetPlan(
  candidateIds: string[],
  perLinkLimit: number,
  taskTotalLimit: number
): Map<string, number> {
  const uniqueCandidateIds = Array.from(new Set(candidateIds));
  const budgets = new Map<string, number>(
    uniqueCandidateIds.map((candidateId) => [candidateId, 0] as const)
  );
  const normalizedPerLinkLimit = normalizeBudget(perLinkLimit);
  const normalizedTaskTotalLimit = normalizeBudget(taskTotalLimit);

  if (
    uniqueCandidateIds.length === 0 ||
    normalizedPerLinkLimit === 0 ||
    normalizedTaskTotalLimit === 0
  ) {
    return budgets;
  }

  const totalBudget = Math.min(
    normalizedTaskTotalLimit,
    uniqueCandidateIds.length * normalizedPerLinkLimit
  );
  const baseAllocation = Math.min(
    normalizedPerLinkLimit,
    Math.floor(totalBudget / uniqueCandidateIds.length)
  );

  for (const candidateId of uniqueCandidateIds) {
    budgets.set(candidateId, baseAllocation);
  }

  let remainder = totalBudget - baseAllocation * uniqueCandidateIds.length;
  while (remainder > 0) {
    let assigned = false;

    for (const candidateId of uniqueCandidateIds) {
      const currentBudget = budgets.get(candidateId) ?? 0;
      if (currentBudget >= normalizedPerLinkLimit) {
        continue;
      }

      budgets.set(candidateId, currentBudget + 1);
      remainder -= 1;
      assigned = true;

      if (remainder === 0) {
        break;
      }
    }

    if (!assigned) {
      break;
    }
  }

  return budgets;
}

export function sampleReviewComments<T extends ReviewSamplingComment>(
  comments: T[],
  targetCount: number,
  negativeKeywords: string[]
): ReviewSamplingResult<T> {
  const uniqueComments = dedupeComments(comments);
  const normalizedTarget = normalizeBudget(targetCount);
  const bucketCounts: Record<ReviewSamplingBucket, number> = {
    latest: 0,
    hot: 0,
    negative: 0
  };

  if (normalizedTarget === 0 || uniqueComments.length === 0) {
    return {
      targetCount: normalizedTarget,
      actualCount: 0,
      sampleInsufficient: normalizedTarget > 0,
      bucketCounts,
      comments: []
    };
  }

  const negativeCommentIds = new Set(
    uniqueComments
      .filter((comment) => isNegativeComment(comment, negativeKeywords))
      .map((comment) => comment.id)
  );
  const negativePool = uniqueComments.filter((comment) => negativeCommentIds.has(comment.id));
  const latestPool = uniqueComments.filter((comment) => !negativeCommentIds.has(comment.id));
  const hotPool = [...latestPool].sort(
    (left, right) =>
      getHotScore(right) - getHotScore(left) ||
      latestPool.findIndex((comment) => comment.id === left.id) -
        latestPool.findIndex((comment) => comment.id === right.id)
  );
  const bucketPools: Record<ReviewSamplingBucket, T[]> = {
    latest: latestPool,
    hot: hotPool,
    negative: negativePool
  };
  const bucketTargets = buildBucketTargets(normalizedTarget, {
    latest: latestPool.length > 0,
    hot: hotPool.length > 0,
    negative: negativePool.length > 0
  });
  const selected: Array<SampledReviewComment<T>> = [];
  const usedIds = new Set<string>();

  for (const bucket of SELECTION_PRIORITY) {
    while (
      bucketCounts[bucket] < bucketTargets[bucket] &&
      pickNextComment(bucket, bucketPools[bucket], usedIds, selected, bucketCounts)
    ) {
      // Continue until this bucket reaches its target or runs out of comments.
    }
  }

  while (selected.length < normalizedTarget) {
    const deficitBucket = SELECTION_PRIORITY.find(
      (bucket) =>
        bucketCounts[bucket] < bucketTargets[bucket] &&
        hasUnusedComment(bucketPools[bucket], usedIds)
    );

    if (deficitBucket) {
      if (pickNextComment(deficitBucket, bucketPools[deficitBucket], usedIds, selected, bucketCounts)) {
        continue;
      }
    }

    const fallbackBucket = FALLBACK_PRIORITY.find((bucket) =>
      hasUnusedComment(bucketPools[bucket], usedIds)
    );

    if (!fallbackBucket) {
      break;
    }

    if (!pickNextComment(fallbackBucket, bucketPools[fallbackBucket], usedIds, selected, bucketCounts)) {
      break;
    }
  }

  return {
    targetCount: normalizedTarget,
    actualCount: selected.length,
    sampleInsufficient: selected.length < normalizedTarget,
    bucketCounts,
    comments: selected
  };
}