import {
  compareUnicodeCodePoints as compare,
  compositeKey,
} from "../unicodeCodePointOrder.js";
import {
  iterateUrlQueryParameters,
  singleQueryValues,
} from "../recordedTransportUrl.js";
import {
  allLines,
  pathSegmentMatches,
  isParam,
  listsAll,
  segmentsOf,
  type StateRecordFacts,
  type StateToolFacts,
  type StateView,
} from "./environmentStateRules.js";
import { pagesOnly } from "./environmentStatePaging.js";

/** A query as replay compares a call's: decoded values by name, in any order; undefined when it repeats a name with another value, which no call's arguments can carry. */
const queryKey = (query: string | undefined): string | undefined => {
  const values = singleQueryValues(query);
  if (values === undefined) return undefined;
  return compositeKey(
    [...values].sort(([left], [right]) => compare(left, right)),
  );
};

interface CheckedLine {
  readonly ordinal: number;
  readonly segments: readonly string[];
  readonly query: string | undefined;
}

/** A list or document view's checked lines, by query, in the tool's recorded order, and which path segments are the tool's parameters. */
export interface CheckedLines {
  readonly params: ReadonlySet<number>;
  readonly byQuery: ReadonlyMap<string, readonly CheckedLine[]>;
  /** The lines listing their whole collection that only page it, which serving answers a call supplying no query from. */
  readonly unfiltered: readonly CheckedLine[];
  /** For a list with a query: the names with a learned role, and the query and whole lines serving evaluates new values on. */
  readonly query?: {
    readonly roles: ReadonlySet<string>;
    readonly lines: readonly CheckedLine[];
  };
}

/** The line a read's call is answered from, and the collection serving lists for it. */
export interface ServedLine {
  readonly ordinal: number;
  readonly collection: string;
  /** Whether the read's query names the line; serving answers a read on any other line in that line's envelope. */
  readonly named: boolean;
  /** Set when serving evaluates the read's own query values on a line it did not name. */
  readonly queried?: boolean;
}

type LineMatch = Pick<ServedLine, "ordinal" | "collection">;

const lineOf = (record: StateRecordFacts): CheckedLine => ({
  ordinal: record.ordinal,
  segments: segmentsOf(record.path),
  query: record.query,
});

/** A query list's roles, and its query and whole lines in the tool's recorded order, which replay keeps among equal matches. */
const queryLines = (
  view: StateView,
  tool: StateToolFacts,
  byOrdinal: ReadonlyMap<number, StateRecordFacts>,
): CheckedLines["query"] => {
  if (view.shape !== "list" || view.query === undefined) return undefined;
  const answered = new Set([...view.query.record_ordinals, ...allLines(view)]);
  return {
    roles: new Set(Object.keys(view.query.parameters)),
    lines: tool.record_ordinals.flatMap((ordinal) => {
      const record = byOrdinal.get(ordinal);
      return record === undefined || !answered.has(ordinal)
        ? []
        : [lineOf(record)];
    }),
  };
};

/** Each list or document view's checked lines. */
export const checkedLines = (input: {
  readonly tools: readonly StateToolFacts[];
  readonly records: readonly StateRecordFacts[];
  readonly views: ReadonlyMap<string, StateView>;
}): Map<string, CheckedLines> => {
  const byOrdinal = new Map(
    input.records.map((record) => [record.ordinal, record]),
  );
  const tools = new Map(input.tools.map((tool) => [tool.name, tool]));
  const byView = new Map<string, CheckedLines>();
  for (const view of input.views.values()) {
    const tool = tools.get(view.tool);
    if (view.shape === "recorded" || view.shape === "item" || !tool) continue;
    const checked = new Set(view.checked_record_ordinals);
    const byQuery = new Map<string, CheckedLine[]>();
    const unfiltered: CheckedLine[] = [];
    for (const ordinal of tool.record_ordinals) {
      const record = byOrdinal.get(ordinal);
      const key = record === undefined ? undefined : queryKey(record.query);
      if (!checked.has(ordinal) || key === undefined) continue;
      const line = lineOf(record!);
      byQuery.set(key, [...(byQuery.get(key) ?? []), line]);
      if (
        view.shape === "list" &&
        listsAll(view, ordinal) &&
        pagesOnly(record!.query)
      )
        unfiltered.push(line);
    }
    const params = new Set(
      segmentsOf(tool.path_template).flatMap((segment, index) =>
        isParam(segment) ? [index] : [],
      ),
    );
    const query = queryLines(view, tool, byOrdinal);
    byView.set(view.tool, {
      params,
      byQuery,
      unfiltered,
      ...(query === undefined ? {} : { query }),
    });
  }
  return byView;
};

/**
 * The checked line serving answers a read's call from, ranked as replay ranks lines: every
 * parameter the read's value verbatim or once percent-decoded and the query the read's, then the
 * most verbatim parameters, then the most query values the read shares, then recorded order. A
 * read with no query falls back, as serving does, on a whole list's lines that only page it.
 */
export const servedLine = (
  lines: CheckedLines | undefined,
  record: StateRecordFacts,
): ServedLine | undefined => {
  const key = queryKey(record.query);
  if (lines === undefined || key === undefined) return undefined;
  const names = [...iterateUrlQueryParameters(record.query ?? "")].map(
    ([name]) => name,
  );
  const named = bestLine(lines, lines.byQuery.get(key) ?? [], record);
  if (named !== undefined) return { ...named, named: true };
  const unfiltered =
    names.length === 0 ? bestLine(lines, lines.unfiltered, record) : undefined;
  if (unfiltered !== undefined) return { ...unfiltered, named: false };
  if (lines.query === undefined) return undefined;
  // As serving does, a read whose every query name has a role answers on a query or whole line, on its own values.
  const { roles } = lines.query;
  if (!names.every((name) => roles.has(name))) return undefined;
  const line = bestLine(lines, lines.query.lines, record);
  return line === undefined
    ? undefined
    : { ...line, named: false, queried: names.length > 0 };
};

/** How many of the read's query names a line recorded with the read's value, as replay counts them. */
const queryMatches = (
  read: ReadonlyMap<string, string>,
  query: string | undefined,
): number => {
  const matched = new Set<string>();
  for (const [name, value] of iterateUrlQueryParameters(query ?? ""))
    if (read.get(name) === value) matched.add(name);
  return matched.size;
};

const bestLine = (
  lines: CheckedLines,
  candidates: readonly CheckedLine[],
  record: StateRecordFacts,
): LineMatch | undefined => {
  const read = segmentsOf(record.path);
  const values = new Map(iterateUrlQueryParameters(record.query ?? ""));
  let best: { line: LineMatch; verbatim: number; query: number } | undefined;
  for (const { ordinal, segments, query } of candidates) {
    if (segments.length !== read.length) continue;
    let verbatim = 0;
    const matches = segments.every((segment, index) => {
      if (segment === read[index]) {
        if (lines.params.has(index)) verbatim += 1;
        return true;
      }
      return (
        lines.params.has(index) &&
        read[index] !== undefined &&
        pathSegmentMatches(segment, read[index])
      );
    });
    if (!matches) continue;
    const matched = queryMatches(values, query);
    if (
      best === undefined ||
      verbatim > best.verbatim ||
      (verbatim === best.verbatim && matched > best.query)
    )
      best = {
        line: { ordinal, collection: `/${segments.join("/")}` },
        verbatim,
        query: matched,
      };
  }
  return best?.line;
};