import type { TimeRecord } from "../shared/record.ts";
import { normalizeTag } from "../shared/tag.ts";


const FOREST_HEADERS = ["Start Time", "End Time", "Tag", "Note", "Tree Type", "Is Success"];

export function parseCsv(text: string): string[][] {
  const rows: string[][] = [];
  let row: string[] = [];
  let field = "";
  let quoted = false;
  const input = text.replace(/^\uFEFF/, "");
  for (let i = 0; i < input.length; i++) {
    const char = input[i]!;
    if (quoted) {
      if (char === '"' && input[i + 1] === '"') { field += '"'; i++; }
      else if (char === '"') quoted = false;
      else field += char;
    } else if (char === '"' && field === "") {
      quoted = true;
    } else if (char === ",") {
      row.push(field); field = "";
    } else if (char === "\n" || char === "\r") {
      if (char === "\r" && input[i + 1] === "\n") i++;
      row.push(field);
      if (row.some(value => value !== "")) rows.push(row);
      row = []; field = "";
    } else {
      field += char;
    }
  }
  if (quoted) throw new Error("CSV has an unfinished quoted field");
  row.push(field);
  if (row.some(value => value !== "")) rows.push(row);
  return rows;
}

function parseForestDate(value: string): number {
  const normalized = value.trim().replace(/([+-]\d{2})(\d{2})$/, "$1:$2");
  const ms = Date.parse(normalized);
  if (!Number.isFinite(ms)) throw new Error(`Invalid Forest timestamp: ${value}`);
  return ms;
}

function hashHex(bytes: ArrayBuffer) {
  return [...new Uint8Array(bytes)].map(value => value.toString(16).padStart(2, "0")).join("");
}

export async function importForestCsv(text: string): Promise<TimeRecord[]> {
  const rows = parseCsv(text);
  if (!rows.length || FOREST_HEADERS.some((header, index) => rows[0]![index]?.trim() !== header)) {
    throw new Error("This is not a Forest CSV with the expected six columns");
  }
  const records: TimeRecord[] = [];
  for (const [index, row] of rows.slice(1).entries()) {
    if (row.length !== 6) throw new Error(`Row ${index + 2} has ${row.length} columns; expected 6`);
    const [rawStart, rawEnd, tag, note, treeType, rawSuccess] = row as [string, string, string, string, string, string];
    const startMs = parseForestDate(rawStart);
    const endMs = parseForestDate(rawEnd);
    if (endMs < startMs) throw new Error(`Row ${index + 2} ends before it starts`);
    if (rawSuccess !== "True" && rawSuccess !== "False") throw new Error(`Row ${index + 2} has an invalid success value`);
    const fingerprint = [rawStart, rawEnd, tag, note, treeType, rawSuccess].join("\u001f");
    const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(fingerprint));
    records.push({
      id: `forest_${hashHex(digest).slice(0, 32)}`,
      startMs, endMs, targetSeconds: null, tag: normalizeTag(tag) || "Unset", note,
      treeType, isSuccess: rawSuccess === "True", source: "forest",
      rawStart, rawEnd, deleted: false,
    });
  }
  return records;
}

function forestDate(ms: number) {
  const date = new Date(ms);
  const pad = (n: number, width = 2) => String(n).padStart(width, "0");
  const offset = -date.getTimezoneOffset();
  const sign = offset >= 0 ? "+" : "-";
  const offsetText = `${sign}${pad(Math.floor(Math.abs(offset) / 60))}${pad(Math.abs(offset) % 60)}`;
  return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(date.getMinutes())}:${pad(date.getSeconds())}.${pad(date.getMilliseconds(), 3)}${offsetText}`;
}

function quote(value: string) {
  return /[",\r\n]/.test(value) ? `"${value.replaceAll('"', '""')}"` : value;
}

export function exportForestCsv(records: TimeRecord[]): string {
  const lines = [FOREST_HEADERS.join(",")];
  for (const record of records.filter(r => !r.deleted && r.endMs !== null).sort((a, b) => a.startMs - b.startMs)) {
    const values = [record.rawStart || forestDate(record.startMs), record.rawEnd || forestDate(record.endMs!),
      record.tag, record.note, record.treeType, record.isSuccess ? "True" : "False"];
    lines.push(values.map(quote).join(","));
  }
  return lines.join("\r\n") + "\r\n";
}