src/lib/parser.ts

export interface UserNode {
  displayName: string;
  username: string;
}

export interface ParseResult {
  relationships: Map<string, { following: UserNode[], followers: UserNode[] }>;
  allUsers: Map<string, UserNode>;
  logs: string[];
}

export function parseSocialData(text: string): ParseResult {
  const result: ParseResult = {
    relationships: new Map(),
    allUsers: new Map(),
    logs: [],
  };

  const addLog = (msg: string) => {
    result.logs.push(`[${new Date().toLocaleTimeString()}] ${msg}`);
  };

  // 1. Clean text
  let cleaned = text.replace(/[\u200B-\u200D\uFEFF]/g, ''); 
  cleaned = cleaned.replace(/\.{3,}/g, '\n'); 

  // Make sure headers are on their own lines
  cleaned = cleaned.replace(/(Following|Followers)(\d+)/gi, '\n$1\n$2\n');

  const rawLines = cleaned.split('\n').map(l => l.trim()).filter(l => l.length > 0);
  addLog(`Started parsing. Extracted ${rawLines.length} raw lines after cleanup.`);

  let currentSubject: string | null = null;
  let currentContext: 'following' | 'followers' | null = null;
  let lastParsedNode: UserNode | null = null;

  let i = 0;
  
  while (i < rawLines.length) {
    const line = rawLines[i];
    
    // Check if header
    if (/^(Following|Followers)$/i.test(line)) {
      const isFollowing = line.toLowerCase() === 'following';
      const newContext = isFollowing ? 'following' : 'followers';
      
      if (i + 1 < rawLines.length && /^\d+$/.test(rawLines[i+1])) {
          i++; // Skip the count line
      }
      
      if (lastParsedNode) {
          if (currentSubject !== lastParsedNode.username) {
              currentSubject = lastParsedNode.username;
              if (!result.relationships.has(currentSubject)) {
                  result.relationships.set(currentSubject, { following: [], followers: [] });
              }
              addLog(`New graph center identified: ${currentSubject} (Tracking ${newContext})`);
              
              // Remove the subject from the previous context's relationships
              for (const rels of result.relationships.values()) {
                  if (rels.following.length > 0 && rels.following[rels.following.length - 1].username === lastParsedNode.username) {
                      rels.following.pop();
                  }
                  if (rels.followers.length > 0 && rels.followers[rels.followers.length - 1].username === lastParsedNode.username) {
                      rels.followers.pop();
                  }
              }
          } else {
              addLog(`Switched context to: ${newContext} for ${currentSubject}`);
          }
      }
      
      currentContext = newContext;
      i++;
      continue;
    }
    
    // Ignore stray numbers
    if (/^\d+$/.test(line)) {
        i++;
        continue;
    }
    
    let displayName = "";
    let username = "";
    
    const nextLine = (i + 1 < rawLines.length) ? rawLines[i+1] : null;
    const nextIsHeaderOrNumber = nextLine && (/^(Following|Followers)$/i.test(nextLine) || /^\d+$/.test(nextLine));
    
    const isUsername = (str: string) => /^@?[a-z0-9._]+$/i.test(str);
    
    // 2-line structure heuristic
    if (nextLine && !nextIsHeaderOrNumber && isUsername(nextLine)) {
        displayName = line;
        username = nextLine;
        i += 2;
    } else {
        // 1-line structure (glued or standalone)
        const match = line.match(/^(.*?)(@?[a-z0-9._]+)$/i);
        if (match && match[2].length > 0) {
            displayName = match[1].trim();
            username = match[2];
            if (!displayName) displayName = username;
        } else {
            displayName = line;
            username = line.replace(/\s+/g, '').toLowerCase(); 
        }
        i++;
    }
    
    username = username.replace(/^@/, '');
    
    // Filter purely numeric edge cases or generic bots
    if (/^\d+$/.test(username) || /^user\d+$/i.test(username)) {
       continue;
    }
    
    const node: UserNode = { displayName, username };
    result.allUsers.set(username, node);
    lastParsedNode = node;
    
    if (currentSubject && currentContext) {
        const rels = result.relationships.get(currentSubject);
        if (rels) {
            rels[currentContext].push(node);
        }
    }
  }
  
  return result;
}

export interface MemberMetrics {
  username: string;
  inDegree: number;
  outDegree: number;
  mutuals: number;
  score: number;
  isAltCandidate?: boolean;
  altOf?: string;
  primaryCenter?: string;
}

export function findShortestPath(data: ParseResult, start: string, end: string): string[] | null {
  if (start === end) return [start];

  // Adjacency list from all relationships
  const adj = new Map<string, Set<string>>();
  
  const addEdge = (u: string, v: string) => {
    if (!adj.has(u)) adj.set(u, new Set());
    adj.get(u)!.add(v);
  };

  data.relationships.forEach((rels, subject) => {
    rels.following.forEach(u => addEdge(subject, u.username));
    rels.followers.forEach(u => addEdge(u.username, subject));
  });

  const queue: [string, string[]][] = [[start, [start]]];
  const visited = new Set<string>([start]);

  while (queue.length > 0) {
    const [node, path] = queue.shift()!;
    if (node === end) return path;

    const neighbors = adj.get(node) || new Set();
    for (const neighbor of neighbors) {
      if (!visited.has(neighbor)) {
        visited.add(neighbor);
        queue.push([neighbor, [...path, neighbor]]);
      }
    }
  }

  return null;
}

export function getCoreMembers(data: ParseResult): MemberMetrics[] {
  const metrics = new Map<string, MemberMetrics>();

  const getOrCreate = (username: string) => {
    if (!metrics.has(username)) {
      metrics.set(username, { username, inDegree: 0, outDegree: 0, mutuals: 0, score: 0 });
    }
    return metrics.get(username)!;
  };

  // Build a set of connections for quick mutual lookup
  const outwardEdges = new Map<string, Set<string>>();

  for (const [subject, rels] of data.relationships.entries()) {
    if (!outwardEdges.has(subject)) outwardEdges.set(subject, new Set());
    const subjectOut = outwardEdges.get(subject)!;

    for (const u of rels.following) {
       subjectOut.add(u.username);
    }
  }

  const centerRep = new Map<string, Map<string, number>>();

  // Calculate degrees and center reps
  for (const [subject, rels] of data.relationships.entries()) {
    const subjNode = getOrCreate(subject);
    
    for (const u of rels.following) {
      subjNode.outDegree++;
      const targetNode = getOrCreate(u.username);
      targetNode.inDegree++;
      
      if (!centerRep.has(u.username)) centerRep.set(u.username, new Map());
      centerRep.get(u.username)!.set(subject, (centerRep.get(u.username)!.get(subject) || 0) + 1);
    }

    for (const u of rels.followers) {
      subjNode.inDegree++;
      const sourceNode = getOrCreate(u.username);
      sourceNode.outDegree++;

      if (!centerRep.has(u.username)) centerRep.set(u.username, new Map());
      centerRep.get(u.username)!.set(subject, (centerRep.get(u.username)!.get(subject) || 0) + 1);

      if (outwardEdges.get(subject)?.has(u.username)) {
          subjNode.mutuals++;
          sourceNode.mutuals++;
      }
    }
  }

  // Calculate a simplified eigenvector-like centrality score
  // Degree + (mutuals * 3)
  for (const m of metrics.values()) {
    m.score = m.inDegree + m.outDegree + (m.mutuals * 3);
    
    // Assign primary center
    if (centerRep.has(m.username)) {
        const reps = Array.from(centerRep.get(m.username)!.entries());
        reps.sort((a, b) => b[1] - a[1]);
        if (reps.length > 0) m.primaryCenter = reps[0][0];
    } else if (data.relationships.has(m.username)) {
         m.primaryCenter = m.username;
    }
  }

  const sorted = Array.from(metrics.values()).sort((a, b) => b.score - a.score);

  // Advanced Algorithm: Alt Detection Heuristic
  for (let i = 0; i < sorted.length; i++) {
    for (let j = i + 1; j < sorted.length; j++) {
      const u1 = sorted[i].username.toLowerCase();
      const u2 = sorted[j].username.toLowerCase();
      if (u1.length < 3 || u2.length < 3) continue;

      // Substring match or common prefix/suffix
      const isSimilar = u1.includes(u2) || u2.includes(u1) || 
                       (u1.slice(0, 5) === u2.slice(0, 5) && Math.abs(u1.length - u2.length) < 3);

      if (isSimilar) {
        // High mutual connection similarity also helps
        const s1 = outwardEdges.get(u1) || new Set();
        const s2 = outwardEdges.get(u2) || new Set();
        let intersection = 0;
        s1.forEach(x => { if (s2.has(x)) intersection++; });
        const union = s1.size + s2.size - intersection;
        const jaccard = union > 0 ? intersection / union : 0;

        if (jaccard > 0.3 || (isSimilar && (s1.size < 5 || s2.size < 5))) {
            if (!sorted[j].isAltCandidate) {
              sorted[j].isAltCandidate = true;
              sorted[j].altOf = u1;
            }
        }
      }
    }
  }

  return sorted;
}

export interface ClusterInfo {
  center: string;
  members: string[];
  color: string;
}

export function detectClusters(data: ParseResult, metrics: MemberMetrics[]): ClusterInfo[] {
  const centers = Array.from(data.relationships.keys());
  const clusters = new Map<string, string[]>();
  
  centers.forEach(c => clusters.set(c, [c]));
  
  metrics.forEach(m => {
    if (m.primaryCenter && m.primaryCenter !== m.username) {
      if (clusters.has(m.primaryCenter)) {
        clusters.get(m.primaryCenter)!.push(m.username);
      }
    }
  });

  const colors = ["#6366f1", "#0ea5e9", "#10b981", "#f59e0b", "#ef4444", "#8b5cf6", "#ec4899", "#14b8a6", "#f97316"];
  
  return Array.from(clusters.entries())
    .map(([center, members], idx) => ({
      center,
      members,
      color: colors[idx % colors.length]
    }))
    .filter(c => c.members.length > 2)
    .sort((a, b) => b.members.length - a.members.length);
}