import { readdir } from "node:fs/promises";
import Fraction from "fraction.js";
import type { RawSimfile } from "./parseSimfile";
import {
  determineBeat,
  mergeSimilarBpmRanges,
  normalizedDifficultyMap,
} from "./util";

const metaTagsToConsume = ["title", "artist"];

const dwiToSMDirection: Record<string, Arrow["direction"]> = {
  0: "0000",
  1: "1100", // down-left
  2: "0100", // down
  3: "0101", // down-right
  4: "1000", // left
  6: "0001", // right
  7: "1010", // up-left
  8: "0010", // up
  9: "0011", // up-right
  A: "0110", // up-down jump
  B: "1001", // left-right jump
};

const smToDwiDirection = Object.entries(dwiToSMDirection).reduce<
  Record<string, string>
>((building, entry) => {
  building[entry[1]] = entry[0];
  return building;
}, {});

type ArrowParseResult = {
  arrows: Arrow[];
  freezes: FreezeBody[];
};

function combinePadsIntoOneStream(
  p1: ArrowParseResult,
  p2: ArrowParseResult,
): ArrowParseResult {
  const arrows = p1.arrows
    .concat(p2.arrows)
    .sort((a, b) => a.offset - b.offset);

  const combinedArrows = arrows.reduce<Arrow[]>((building, arrow, i, rest) => {
    const prevArrow = rest[i - 1];

    // since previous offset matches, the previous one already
    // grabbed and combined with this arrow, throw it away
    if (prevArrow?.offset === arrow.offset) {
      return building;
    }

    const nextArrow = rest[i + 1];

    if (nextArrow?.offset === arrow.offset) {
      return building.concat({
        ...arrow,
        direction: arrow.direction + nextArrow.direction,
      } as Arrow);
    }

    return building.concat({
      ...arrow,
      direction: p1.arrows.includes(arrow)
        ? `${arrow.direction}0000`
        : `0000${arrow.direction}`,
    } as Arrow);
  }, []);

  const bumpedP2Freezes = p2.freezes.map((f) => {
    return {
      ...f,
      direction: f.direction + 4,
    } as FreezeBody;
  });

  const freezes = p1.freezes
    .concat(bumpedP2Freezes)
    .sort((a, b) => a.startOffset - b.startOffset);

  return {
    arrows: combinedArrows,
    freezes,
  };
}

function findFirstNonEmptyMeasure(
  p1Notes: string,
  p2Notes: string | undefined,
): number {
  let i = 0;

  while (
    p1Notes.startsWith("00000000") &&
    (!p2Notes || p2Notes.startsWith("00000000"))
  ) {
    p1Notes = p1Notes.substring(8);
    p2Notes = p2Notes?.substring(8);
    i += 8;
  }

  return i;
}

function parseArrowStream(
  notes: string,
  firstNonEmptyMeasureIndex: number,
): ArrowParseResult {
  const arrows: Arrow[] = [];
  const freezes: FreezeBody[] = [];

  let currentFreezeDirections: string[] = [];
  const openFreezes: Record<
    FreezeBody["direction"],
    Partial<FreezeBody> | null
  > = {
    0: null,
    1: null,
    2: null,
    3: null,
    4: null,
    5: null,
    6: null,
    7: null,
  };

  let curOffset = new Fraction(0);
  // dwi's default increment is 8th notes
  let curMeasureFraction = new Fraction(1).div(8);

  for (
    let i = firstNonEmptyMeasureIndex;
    i < notes.length && notes[i] !== ";";
    ++i
  ) {
    let note = notes[i];
    const nextNote = notes[i + 1];

    const smDirection = dwiToSMDirection[note];

    // give the current note a chance to conclude any freezes that may be pending
    if (smDirection) {
      const smDirectionSplit = smDirection.split("");
      for (let d = 0; d < smDirection.length; ++d) {
        if (
          smDirection[d] === "1" &&
          openFreezes[d as FreezeBody["direction"]]
        ) {
          const of = openFreezes[d as FreezeBody["direction"]];
          of!.endOffset = curOffset.n / curOffset.d + 0.25;
          freezes.push(of as FreezeBody);
          openFreezes[d as FreezeBody["direction"]] = null;
          smDirectionSplit[d] = "0";
        }
      }

      note = smToDwiDirection[smDirectionSplit.join("")];
    }

    if (nextNote === "!") {
      // B!602080B
      // this means the freeze starts with B (left and right), but then only right (6) has the freeze body
      // during the freeze there is down (2) then up (8), concluding with the second B

      const freezeNote = notes[i + 2];

      const smDirection = dwiToSMDirection[freezeNote];

      for (let d = 0; d < smDirection.length; ++d) {
        if (smDirection[d] === "1") {
          openFreezes[d as FreezeBody["direction"]] = {
            direction: d as FreezeBody["direction"],
            startOffset: curOffset.n / curOffset.d,
          };
        }
      }

      // the head of a freeze is still an arrow
      arrows.push({
        direction: dwiToSMDirection[note].replace(
          /1/g,
          "2",
        ) as Arrow["direction"],
        beat: determineBeat(curOffset),
        offset: curOffset.n / curOffset.d,
      });

      // remember the direction to know when to close the freeze
      currentFreezeDirections.push(freezeNote);

      // move past the exclamation and trailing note
      i += 2;
      curOffset = curOffset.add(curMeasureFraction);
    } else if (note === "(") {
      curMeasureFraction = new Fraction(1).div(16);
    } else if (note === "[") {
      curMeasureFraction = new Fraction(1).div(24);
    } else if (note === "{") {
      curMeasureFraction = new Fraction(1).div(64);
    } else if (note === "`") {
      curMeasureFraction = new Fraction(1).div(192);
    } else if ([")", "]", "}", "'"].includes(note)) {
      curMeasureFraction = new Fraction(1).div(8);
    } else if (note === "0") {
      curOffset = curOffset.add(curMeasureFraction);
    } else {
      const direction = dwiToSMDirection[note];

      if (direction) {
        arrows.push({
          direction,
          beat: determineBeat(curOffset),
          offset: curOffset.n / curOffset.d,
        });
      }

      curOffset = curOffset.add(curMeasureFraction);
    }
  }

  return { arrows, freezes };
}

async function findBanner(titlePath: string): Promise<string> {
  const files = await readdir(titlePath);

  const bannerFile = files.find(
    (f) => f.endsWith(".png") && f.indexOf("-bg.png") === -1,
  );

  return bannerFile ?? null;
}

async function parseDwi(dwi: string, titlePath?: string): Promise<RawSimfile> {
  let bpm: string | null = null;
  let changebpm: string | null = null;
  let displaybpm: string | null = null;
  let stops: string | null = null;

  const lines = dwi.split("\n").map((l) => l.trim());

  let i = 0;

  const sc: Partial<RawSimfile> = {
    charts: {},
    availableTypes: [],
    banner: titlePath ? await findBanner(titlePath) : null,
  };

  function parseNotes(mode: "single" | "double", rawNotes: string) {
    const values = rawNotes.split(":");
    const difficulty = normalizedDifficultyMap[values[0].toLowerCase()];
    const feet = Number(values[1]);
    const notes = values[2];
    const playerTwoNotes = values[3];

    const firstNonEmptyMeasureIndex = findFirstNonEmptyMeasure(
      notes,
      playerTwoNotes,
    );

    let arrowResult = parseArrowStream(notes, firstNonEmptyMeasureIndex);

    if (mode === "double") {
      const playerTwoResult = parseArrowStream(
        playerTwoNotes,
        firstNonEmptyMeasureIndex,
      );

      arrowResult = combinePadsIntoOneStream(arrowResult, playerTwoResult);
    }

    sc.availableTypes!.push({
      slug: `${mode}-${difficulty}`,
      mode,
      difficulty: difficulty as any,
      feet,
    });

    sc.charts![`${mode}-${difficulty}`] = {
      arrows: arrowResult.arrows,
      freezes: arrowResult.freezes,
      bpm: determineBpm(firstNonEmptyMeasureIndex),
      stops: determineStops(firstNonEmptyMeasureIndex),
    };
  }

  function determineStops(emptyOffset: number) {
    if (!stops) {
      return [];
    }

    return stops.split(",").map((s) => {
      const [eigthNoteS, stopDurationS] = s.split("=");

      return {
        offset: Number(eigthNoteS) * (1 / 16) - emptyOffset * (1 / 8),
        duration: Number(stopDurationS),
      };
    });
  }

  function determineBpm(emptyOffset: number) {
    let finalBpms: Bpm[] = [];

    if (bpm && !Number.isNaN(Number(bpm))) {
      finalBpms = [{ startOffset: 0, endOffset: null, bpm: Number(bpm) }];
    }

    if (changebpm) {
      if (!finalBpms) {
        throw new Error("parseDwi: a simfile has changebpm but not bpm");
      }

      const entries = changebpm.split(",");
      const additionalBpms = entries.map((bpmES, i, a) => {
        const [eigthNoteS, bpmVS] = bpmES.split("=");
        const nextEigthNoteS = a[i + 1]?.split("=")[0] ?? null;

        const startOffset =
          Number(eigthNoteS) * (1 / 16) - emptyOffset * (1 / 8);
        let endOffset = null;

        if (nextEigthNoteS) {
          endOffset = Number(nextEigthNoteS) * (1 / 16) - emptyOffset * (1 / 8);
        }

        return {
          startOffset,
          endOffset,
          bpm: Number(bpmVS),
        };
      });

      finalBpms = finalBpms.concat(additionalBpms);
      finalBpms[0].endOffset = finalBpms[1].startOffset;
    }

    if (!finalBpms) {
      throw new Error("parseDwi, determineBpm: failed to get bpm");
    }

    finalBpms = mergeSimilarBpmRanges(finalBpms);

    if (displaybpm) {
      if (!Number.isNaN(Number(displaybpm))) {
        sc.displayBpm = displaybpm;
      } else if (displaybpm.indexOf("..") > -1) {
        const [min, max] = displaybpm.split("..");
        sc.displayBpm = `${min}-${max}`;
      } else {
        // displayBpm is allowed to be '*', I know of no simfiles
        // that actually do that though
        sc.displayBpm = displaybpm;
      }
    } else {
      const minBpm = Math.min(...finalBpms.map((b) => b.bpm));
      const maxBpm = Math.max(...finalBpms.map((b) => b.bpm));

      if (minBpm === maxBpm) {
        sc.displayBpm = Math.round(minBpm).toString();
      } else {
        sc.displayBpm = `${Math.round(minBpm)}-${Math.round(maxBpm)}`;
      }
    }

    return finalBpms;
  }

  function parseTag(lines: string[], index: number): number {
    const line = lines[index];

    const r = /#([A-Za-z]+):([^;]*)/;
    const result = r.exec(line);

    if (result) {
      const tag = result[1].toLowerCase();
      const value = result[2];

      if (metaTagsToConsume.includes(tag)) {
        // @ts-ignore
        sc[tag] = value;
      } else if (tag === "displaybpm") {
        displaybpm = value;
      } else if (tag === "bpm") {
        bpm = value;
      } else if (tag === "changebpm") {
        changebpm = value;
      } else if (tag === "freeze") {
        stops = value;
      } else if (tag === "single" || tag === "double") {
        parseNotes(tag, value);
      }
    }

    return index + 1;
  }

  try {
    while (i < lines.length) {
      const line = lines[i];

      if (!line.length || line.startsWith("//")) {
        i += 1;
        continue;
      }

      if (line.startsWith("#")) {
        i = parseTag(lines, i);
      } else {
        i += 1;
      }
    }

    if (!displaybpm && !bpm) {
      throw new Error(`No BPM found for ${titlePath}`);
    }

    return sc as RawSimfile;
  } catch (e) {
    const message = e instanceof Error ? e.message : String(e);
    const stack = e instanceof Error ? e.stack : "";

    throw new Error(`error, ${message}, ${stack}, parsing ${dwi}`);
  }
}

export { parseDwi };