import { Term } from "n3";

type SuffixesNode = { usedBy?: string; children: Map<string, SuffixesNode> };
type DisplayNode = { label?: string; link?: string };

export class SuffixLabels {
  displayNodes: Map<string, DisplayNode>;
  usedSuffixes: SuffixesNode;
  constructor() {
    this.displayNodes = new Map();
    this.usedSuffixes = { usedBy: undefined, children: new Map() };
  }

  planDisplayForNode(node: Term) {
    const uri = node.value;
    this._planDisplayForUri(uri);
  }

  _planDisplayForUri(uri: string) {
    if (this.displayNodes.has(uri)) {
      return;
    }

    const segments = uri.split("/");
    let curs = this.usedSuffixes;
    let label: string | undefined = undefined;

    for (let i = segments.length - 1; i >= 0; i--) {
      const seg = segments[i];
      if (curs.usedBy && curs.usedBy != uri) {
        this._prependClashingUri(curs);
      }

      if (!curs.children.has(seg)) {
        const child: SuffixesNode = { usedBy: undefined, children: new Map() };
        curs.children.set(seg, child);

        if (label === undefined) {
          label = SuffixLabels._tailSegments(uri, segments.length - i);
          child.usedBy = uri;
        }
      }
      curs = curs.children.get(seg)!;
    }
    this.displayNodes.set(uri, { label: label });
  }

  _prependClashingUri(curs: SuffixesNode) {
    // Claim: When a clash is discovered, only 1 uri needs to
    // change its length, and there will be only one child node to
    // follow, and the clashing uri can be changed to prepend that
    // one child (since we'll see it again if that one wasn't
    // enough).
    const clashNode: DisplayNode = this.displayNodes.get(curs.usedBy!)!;
    const nextLeftSeg = curs.children.entries().next().value;
    if (nextLeftSeg[1].usedBy) {
      throw new Error("unexpected");
    }

    clashNode.label = nextLeftSeg[0] + "/" + clashNode.label;
    nextLeftSeg[1].usedBy = curs.usedBy;
    curs.usedBy = undefined;
  }

  // a substring to show for this uri
  getLabelForNode(node: string) {
    const dn = this.displayNodes.get(node);
    if (dn === undefined) {
      throw new Error(`you never called planDisplayForNode on ${node}`);
    }
    return dn.label;
  }

  static _tailSegments(uri: string, n: number) {
    let i = uri.length;
    for (let rep = 0; rep < n; rep++) {
      i = uri.lastIndexOf("/", i - 1);
    }
    return uri.substr(i + 1);
  }
}