const WEEKS_BEFORE_LAST_FROST = 10;
const FALL_FACTOR = 2;

function range(start, end) {
  const size = end - start;
  const array = new Array(size);
  for(let i = start; i < end; i++) {
    array[i - start] = i;
  }
  return array;
}

function daysLater(date, n) {
  return new Date(date.getTime() + n * 24 * 60 * 60 * 1000);
}

function weeksLater(date, n) {
  return daysLater(date, n * 7);
}

function seasonLengthInWeeks(lastFrostDate, firstFrostDate) {
  const oneWeek = 7 * 24 * 60 * 60 * 1000;
  const dt = firstFrostDate.getTime() - lastFrostDate.getTime();
  return Math.floor(dt / oneWeek);
}

function seasonWeeks(lastFrostDate, seasonLength) {
  return range(-WEEKS_BEFORE_LAST_FROST, seasonLength + 3).map(offset => {
    return {
      date: weeksLater(lastFrostDate, offset),
      offset: offset
    };
  });
}

class Season {
  constructor(lastFrostDate, firstFrostDate) {
    this.lastFrostDate = lastFrostDate;
    this.firstFrostDate = firstFrostDate;
    this.length = seasonLengthInWeeks(lastFrostDate, firstFrostDate);
    this.weeks = seasonWeeks(lastFrostDate, this.length);
  }
}

class Crop {
  constructor(name, {depth, fallCrop, family, headStart, interval, maturity, multisow,
                     overwinterPlant, pause, references, spacing, springPlant, resume,
                     species, transplant, trellis}) {
    // Seed planting depth in inches.
    this.depth = depth || .25;
    // Plant again in the fall?
    this.fallCrop = fallCrop;
    // Broad category (brassica, cucurbit, nightshade, etc.)
    this.family = family;
    // Weeks spent indoors before transplanting.
    this.headStart = headStart || 0;
    // Succession planting interval (weeks)
    this.interval = interval || 0;
    // Average time to maturity from transplanting or sowing (weeks)
    this.maturity = maturity;
    // Seeds per module
    this.multisow = multisow || 1;
    // Human readable name
    this.name = name;
    // Overwintered crops are fall crops but they are not subject to
    // the same rules as plants that are harvested the same year.
    // Instead of planting them relative to their time to maturity,
    // they are planted relative to the first frost date so they can
    // be harvested in the spring/summer of the following year.
    this.overwinterPlant = overwinterPlant;
    // When to pause succession planting (weeks after last frost)
    this.pause = pause || 99;
    // External links to helpful information about the crop.
    this.references = references || [];
    // When to resume succession planting (weeks before first frost)
    this.resume = resume || 99;
    // Plants per square foot, or, in the case of multisowing, clumps
    // per square foot.
    this.spacing = spacing || 1;
    // Latin names.
    this.species = species || [];
    // Earliest sowing/transplanting week (offset relative to last
    // frost date.) Null if the crop should not be planted in the
    // spring.
    this.springPlant = springPlant;
    // Transplanted or direct sown?
    this.transplant = transplant || false;
    // Needs a trellis?
    this.trellis = trellis || false;
  }
}

const CROPS = [
  new Crop("Amaranth", {
    depth: 0.125,
    family: "Amaranth",
    headStart: 4,
    maturity: 5,
    spacing: 4,
    springPlant: 0,
    species: ["amaranth tricolor"],
    transplant: true
  }),
  new Crop("Arugula", {
    family: "Brassica",
    fallCrop: true,
    headStart: 4,
    maturity: 6,
    multisow: 3,
    pause: 3,
    resume: 11,
    spacing: 4,
    species: ["eruca sativa"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Basil", {
    family: "Mint",
    headStart: 5,
    maturity: 6,
    species: ["ocimum basilicum"],
    springPlant: 2,
    transplant: true
  }),
  new Crop("Bean (Bush)", {
    depth: 1,
    family: "Legume",
    headStart: 3,
    interval: 3,
    maturity: 8,
    spacing: 9,
    species: ["phaseolus vulgaris"],
    springPlant: 1,
    transplant: true,
    transplantIterations: 1
  }),
  new Crop("Bean (Pole)", {
    depth: 1,
    family: "Legume",
    headStart: 2,
    maturity: 9,
    spacing: 8,
    species: ["phaseolus vulgaris"],
    springPlant: 1,
    transplant: true,
    trellis: true
  }),
  new Crop("Beet", {
    depth: .5,
    family: "Amaranth",
    headStart: 4,
    interval: 3,
    maturity: 8,
    multisow: 3,
    pause: 1,
    resume: 12,
    spacing: 4,
    species: ["beta vulgaris"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Bok Choy", {
    fallCrop: true,
    family: "Brassica",
    headStart: 2,
    maturity: 7,
    spacing: 4,
    species: ["brassica rapa"],
    springPlant: -2,
    transplant: true
  }),
  new Crop("Broccoli", {
    fallCrop: true,
    family: "Brassica",
    headStart: 4,
    maturity: 12,
    species: ["brassica oleracea"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Brussels Sprouts", {
    fallCrop: true,
    family: "Brassica",
    headStart: 6,
    maturity: 16,
    species: ["brassica oleracea"],
    transplant: true
  }),
  new Crop("Cabbage (Early)", {
    family: "Brassica",
    fallCrop: true,
    headStart: 4,
    maturity: 8,
    species: ["brassica oleracea"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Cabbage (Late)", {
    family: "Brassica",
    fallCrop: true,
    headStart: 4,
    maturity: 14,
    species: ["brassica oleracea"],
    transplant: true
  }),
  new Crop("Cabbage (Asian)", {
    family: "Brassica",
    fallCrop: true,
    headStart: 2,
    maturity: 8,
    species: ["brassica rapa"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Cauliflower", {
    family: "Brassica",
    fallCrop: true,
    headStart: 4,
    maturity: 10,
    species: ["brassica oleracea"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Carrot", {
    family: "Umbellifer",
    interval: 4,
    maturity: 10,
    spacing: 16,
    species: ["daucus carota"],
    springPlant: -4
  }),
  new Crop("Cilantro", {
    family: "Umbellifer",
    interval: 3,
    maturity: 7,
    species: ["coriandrum sativum"],
    springPlant: 0
  }),
  new Crop("Claytonia", {
    fallCrop: true,
    family: "Montiaceae",
    headStart: 4,
    maturity: 6,
    spacing: 9,
    species: ["montia perfoliata"],
    springPlant: -5,
    transplant: true
  }),
  new Crop("Cucumber", {
    depth: .5,
    family: "Cucurbit",
    headStart: 4,
    maturity: 9,
    spacing: 2,
    species: ["cucumis sativus"],
    springPlant: 1,
    transplant: true,
    trellis: true
  }),
  new Crop("Dill", {
    family: "Umbellifer",
    fallCrop: true,
    headStart: 3,
    maturity: 8,
    spacing: 4,
    species: ["anethum graveolens"],
    springPlant: -2,
    transplant: true
  }),
  new Crop("Eggplant", {
    family: "Nightshade",
    headStart: 8,
    maturity: 11,
    species: ["solanum melongena"],
    springPlant: 3,
    transplant: true
  }),
  new Crop("Endive", {
    depth: .125,
    family: "Aster",
    headStart: 4,
    maturity: 4,
    species: ["cichorium endivia"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Fennel", {
    fallCrop: true,
    family: "Umbellifer",
    headStart: 4,
    maturity: 10,
    spacing: 4,
    species: ["foeniculum vulgare"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Garlic", {
    depth: 3,
    family: "Allium",
    fallCrop: true,
    overwinterPlant: 2,
    maturity: 28,
    spacing: 4,
    species: ["allium sativum"]
  }),
  new Crop("Kale", {
    fallCrop: true,
    family: "Brassica",
    headStart: 4,
    maturity: 4,
    species: ["brassica napus", "brassica oleracea"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Leek (Summer)", {
    depth: 0.5,
    family: "Allium",
    headStart: 6,
    maturity: 10,
    multisow: 4,
    spacing: 1,
    species: ["allium ampeloprasum"],
    springPlant: -2,
    transplant: true
  }),
  new Crop("Lettuce (Leaf)", {
    depth: .125,
    family: "Aster",
    headStart: 4,
    interval: 2,
    maturity: 7,
    pause: 3,
    resume: 11,
    spacing: 4,
    species: ["latuca sativa"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Mache (Corn Salad)", {
    family: "Honeysuckle",
    interval: 2,
    maturity: 7,
    pause: 1,
    resume: 11,
    spacing: 16,
    species: ["valerianella locusta"],
    springPlant: -4
  }),
  new Crop("Mustard Greens", {
    family: "Brassica",
    headStart: 3,
    interval: 3,
    maturity: 6,
    pause: 1,
    resume: 10,
    spacing: 4,
    species: ["brassica juncea", "brassica rapa"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Onion", {
    depth: 0.5,
    family: "Allium",
    headStart: 6,
    maturity: 14,
    multisow: 4,
    references: [
      {
        title: "Charles Dowding - Grow onions and spring onions from seed",
        url: "https://www.youtube.com/watch?v=1k0f4GoC6Zw"
      }
    ],
    spacing: 1,
    species: ["allium cepa"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Parsley", {
    family: "Umbellifer",
    headStart: 6,
    maturity: 7,
    spacing: 4,
    species: ["petroselinum crispum"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Parsnip", {
    depth: .5,
    family: "Umbellifer",
    maturity: 14,
    spacing: 4,
    species: ["pastinaca sativa"],
    springPlant: -2
  }),
  new Crop("Pea", {
    fallCrop: 'sow',
    family: "Legume",
    headStart: 2,
    maturity: 12,
    multisow: 4,
    spacing: 4,
    species: ["pisum sativum"],
    springPlant: -3,
    transplant: true,
    trellis: true
  }),
  new Crop("Pepper", {
    family: "Nightshade",
    headStart: 8,
    maturity: 10,
    species: ["capsicum annuum"],
    springPlant: 3,
    transplant: true
  }),
  new Crop("Potato", {
    depth: 3,
    family: "Nightshade",
    maturity: 12,
    spacing: 4,
    species: ["solanum tuberosum"],
    springPlant: -3
  }),
  new Crop("Radish (Spring)", {
    depth: .5,
    family: "Brassica",
    headStart: 3,
    interval: 3,
    maturity: 4,
    multisow: 5,
    pause: 4,
    resume: 10,
    spacing: 4,
    species: ["raphanus raphanistrum"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Radish (Winter)", {
    depth: .5,
    family: "Brassica",
    fallCrop: true,
    headStart: 3,
    maturity: 9,
    spacing: 4,
    species: ["raphanus raphanistrum"],
    transplant: true
  }),
  new Crop("Shallot", {
    family: "Allium",
    headStart: 6,
    maturity: 9,
    multisow: 3,
    spacing: 4,
    species: ["allium cepa"],
    springPlant: -4,
    transplant: true
  }),
  new Crop("Spinach", {
    depth: .5,
    family: "Amaranth",
    fallCrop: true,
    headStart: 3,
    maturity: 6,
    multisow: 3,
    pause: -1,
    resume: 11,
    spacing: 4,
    species: ["spinacia olerace"],
    springPlant: -5,
    transplant: true
  }),
  new Crop("Squash (Summer)", {
    depth: 1,
    family: "Cucurbit",
    headStart: 4,
    maturity: 8,
    spacing: 1.0 / 9,
    species: ["cucurbita pepo"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Squash (Winter)", {
    depth: 1,
    family: "Cucurbit",
    headStart: 4,
    maturity: 12,
    spacing: 0.5,
    species: ["cucurbita maxima", "cucurbita moschata", "cucurbita pepo"],
    springPlant: 1,
    transplant: true
  }),
  new Crop("Swiss Chard", {
    depth: .5,
    family: "Amaranth",
    headStart: 4,
    maturity: 4,
    spacing: 4,
    species: ["beta vulgaris"],
    springPlant: 2,
    transplant: true
  }),
  new Crop("Tomato (Indeterminate)", {
    family: "Nightshade",
    headStart: 7,
    maturity: 11,
    species: ["lycopersicon esculentum"],
    springPlant: 3,
    transplant: true,
    trellis: true
  }),
  new Crop("Turnip", {
    family: "Brassica",
    fallCrop: true,
    headStart: 3,
    maturity: 5,
    multisow: 5,
    pause: 6,
    resume: 10,
    spacing: 4,
    species: ["brassica rapa"],
    springPlant: -3,
    transplant: true
  }),
  new Crop("Alyssum", {
    family: "Brassica",
    headStart: 4,
    maturity: 8,
    species: ["lobularia maritima"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Amaranth (Flower)", {
    family: "Amaranth",
    headStart: 4,
    maturity: 12,
    species: ["amaranthus caudatus"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Borage", {
    family: "Borage",
    maturity: 7,
    species: ["borago officinalis"],
    springPlant: 0
  }),
  new Crop("Calendula", {
    family: "Aster",
    headStart: 4,
    maturity: 11,
    species: ["calendula officinalis"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Cornflower", {
    family: "Aster",
    headStart: 4,
    maturity: 12,
    spacing: 4,
    species: ["centaurea cyanus"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Cosmos", {
    family: "Aster",
    headStart: 4,
    maturity: 12,
    species: ["cosmos bipinnatus"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Larkspur", {
    family: "Buttercup",
    headStart: 4,
    maturity: 11,
    spacing: 3,
    species: ["consolida ajacis"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Marigold", {
    family: "Aster",
    headStart: 4,
    maturity: 11,
    species: ["Tagetes erecta", "tagetes patula"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Mexican Sunflower", {
    family: "Aster",
    headStart: 4,
    maturity: 12,
    species: ["tithonia rotundifolia"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Nasturtium", {
    depth: 0.5,
    family: "Tropaeolum",
    headStart: 2,
    maturity: 8,
    species: ["tropaeolum majus"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Nigella", {
    family: "Buttercup",
    headStart: 4,
    maturity: 10,
    species: ["nigella hispanica"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Strawflower", {
    family: "Aster",
    headStart: 8,
    maturity: 10,
    species: ["xerochrysum bracteatum"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Sunflower", {
    family: "Helianthus",
    headStart: 2,
    maturity: 11,
    species: ["helianthus annuus"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Sweet Pea", {
    depth: 0.5,
    family: "Legume",
    headStart: 8,
    maturity: 10,
    species: ["lathyrus odoratus"],
    springPlant: 0,
    transplant: true
  }),
  new Crop("Zinnia", {
    family: "Aster",
    headStart: 4,
    maturity: 7,
    species: ["zinnia elegans"],
    springPlant: 0,
    transplant: true
  })
];

function makeCropSchedule(crop, season) {
  function isSuccession(offset) {
    const start = offset <= crop.pause ? crop.springPlant : crop.resume;
    return crop.interval > 0 &&
      offset != crop.springPlant &&
      offset >= crop.springPlant &&
      offset <= fallPlant &&
      (offset <= crop.pause || offset >= resume) &&
      (offset - start) % crop.interval == 0;
  }

  function isSuccessionStart(offset) {
    offset += crop.headStart;
    const start = offset <= crop.pause ? crop.springPlant : crop.resume;
    return crop.interval > 0 &&
      crop.transplant &&
      offset != crop.springPlant &&
      offset >= crop.springPlant &&
      offset <= fallPlant &&
      (offset <= crop.pause || offset >= resume) &&
      (offset - start) % crop.interval == 0;
  }

  const springStart = crop.springPlant - crop.headStart;
  const fallPlant = season.length - crop.maturity - FALL_FACTOR;
  const fallStart = fallPlant - crop.headStart;
  const resume = season.length - crop.resume;

  return season.weeks.map(week => {
    const actions = [];

    if(crop.transplant && week.offset == springStart) {
      actions.push("start");
    } else if(crop.transplant && week.offset == crop.springPlant) {
      actions.push("transplant");
    } else if(week.offset == crop.springPlant) {
      actions.push("sow");
    }

    if(isSuccession(week.offset)) {
      actions.push(crop.transplant ? "transplant" : "sow");
    }
    if(isSuccessionStart(week.offset)) {
      actions.push("start");
    }

    if(crop.fallCrop) {
      if(crop.overwinterPlant) {
        if(week.offset == season.length + crop.overwinterPlant) {
          actions.push("sow");
        }
      } else if(crop.transplant && week.offset == fallStart) {
        actions.push("start");
      } else if(crop.transplant && week.offset == fallPlant) {
        actions.push("transplant");
      } else if(week.offset == fallPlant) {
        actions.push("sow");
      }
    }

    return {
      date: weeksLater(season.lastFrostDate, week.offset),
      actions: actions
    };
  });
}

function clearElement(element) {
  while (element.firstChild) {
    element.removeChild(element.firstChild);
  }
}

function makeSchedule(crops, season) {
  const schedule = {};
  crops.forEach(crop => {
    schedule[crop.name] = makeCropSchedule(crop, season);
  });
  return schedule;
}

function monthAndDay(date) {
  return (date.getUTCMonth() + 1) + "/" + date.getUTCDate();
}

function viewCropDetails(crop) {
  function close() {
    container.removeChild(overlay);
  }

  function addDetail(name, detail) {
    const p = document.createElement("p");
    p.appendChild(document.createTextNode(`${name}: ${detail}`));
    modal.appendChild(p);
  }

  function addReferences() {
    if(crop.references.length > 0) {
      const div = document.createElement("div");
      const title = document.createElement("span");
      const list = document.createElement("ul");
      title.appendChild(document.createTextNode("References"));
      div.appendChild(title);
      crop.references.forEach(ref => {
        const li = document.createElement("li");
        const link = document.createElement("a");
        link.appendChild(document.createTextNode(ref.title));
        link.href = ref.url;
        link.target = "_blank"; // open in new tab.
        li.appendChild(link);
        list.appendChild(li);
      });
      div.appendChild(list);
      modal.appendChild(div);
    }
  }

  const container = document.getElementById("container");
  const overlay = document.createElement("div");
  const modal = document.createElement("div");
  const heading = document.createElement("h2");
  const subheading = document.createElement("span");
  const speciesDetail = `(${crop.species.join(", ")}) - ${crop.family} family`;
  heading.appendChild(document.createTextNode(crop.name));
  subheading.appendChild(document.createTextNode(speciesDetail));
  subheading.classList.add("detail-subheading");
  heading.appendChild(subheading);
  modal.classList.add("modal");
  modal.appendChild(heading);
  addDetail("Average time to maturity",
            `${crop.maturity} weeks from ${crop.transplant ? "transplant" : "seed"}`);
  if(crop.springPlant == -1) {
    addDetail("Spring planting time", `1 week before last frost`);
  } else if(crop.springPlant < 0) {
    addDetail("Spring planting time",
              `${Math.abs(crop.springPlant)} weeks before last frost`);
  } else if(crop.springPlant == 1) {
    addDetail("Spring planting time", `1 week after last frost`);
  } else if(crop.springPlant > 0) {
    addDetail("Spring planting time",
              `${crop.springPlant} weeks after last frost`);
  } else if(crop.springPlant == 0) {
    addDetail("Spring planting time", "On the last frost date");
  } else {
    addDetail("Spring planting time", "Not a spring crop");
  }
  if(crop.fallCrop) {
    addDetail("Fall planting time", `${crop.maturity + FALL_FACTOR} weeks before first frost`);
  } else if(crop.resume != 99) {
    addDetail("Fall planting time", `Succession planted ${crop.resume} weeks before first frost`);
  } else if(crop.interval > 0) {
    addDetail("Fall planting time", `Succession planted until ${crop.maturity + FALL_FACTOR} weeks before first frost`);
  } else {
    addDetail("Fall planting time", "Not a fall crop");
  }
  addDetail("Planting method", crop.transplant ? "Transplant" : "Direct sow");
  if(crop.transplant) {
    addDetail("Start indoors", `${crop.headStart} weeks before planting`);
  }
  if(crop.interval > 0) {
    addDetail("Succession planting interval", `Every ${crop.interval} weeks`);
  }
  if(crop.multisow > 1) {
    addDetail("Multisow", `${crop.multisow} plants per hole (after thinning)`);
  } else {
    addDetail("Multisow", "No");
  }
  if(crop.spacing >= 1) {
    addDetail("Spacing", `${crop.spacing} ${crop.multisow > 1 ? "clump(s)" : "plant(s)"} per square foot`);
  } else {
    addDetail("Spacing", `1 per ${Math.floor(1 / crop.spacing)} square feet`);
  }
  addDetail("Seed planting depth", `${crop.depth}"`);
  addDetail("Needs a trellis", crop.trellis ? "Yes" : "No");
  addReferences();
  overlay.classList.add("overlay");
  overlay.appendChild(modal);
  container.appendChild(overlay);
  overlay.addEventListener("click", event => close());
}

function makeDetailLink(crop) {
  const span = document.createElement("span");
  span.classList.add("crop");
  span.appendChild(document.createTextNode(crop.name));
  span.addEventListener("click", event => {
    viewCropDetails(crop);
  });
  return span;
}

function refreshTable(crops, season, schedule) {
  function createWeeksRow(season) {
    const row = document.createElement("tr");
    row.appendChild(document.createElement("th"));
    season.weeks.forEach(week => {
      const td = document.createElement("th", {scope: "col"});
      const firstFrost = week.offset == 0;
      const lastFrost = week.offset == season.length;
      const dateString = monthAndDay(week.date);
      const label = firstFrost || lastFrost ?  `${dateString}❄`: dateString;
      const text = document.createTextNode(label);
      td.appendChild(text);
      row.appendChild(td);
    });
    return row;
  }

  function createHeader(season) {
    const thead = document.createElement("thead");
    const row = document.createElement("tr");
    ["Crop", "Week"].forEach(column => {
      const th = document.createElement("th", {scope: "col"});
      const text = document.createTextNode(column);
      th.appendChild(text);
      row.appendChild(th);
    });
    thead.appendChild(row);
    thead.appendChild(createWeeksRow(season));
    return thead;
  }

  function createCropRow(crop, schedule) {
    function icon(name) {
      const icon = document.createElement("span");
      icon.classList.add("icon");
      icon.classList.add(`icon-${name}`);
      return icon;
    }

    const row = document.createElement("tr");
    const th = document.createElement("td");
    th.appendChild(makeDetailLink(crop));
    row.appendChild(th);
    schedule.forEach(week => {
      const td = document.createElement("td");
      td.title = monthAndDay(week.date);
      week.actions.forEach(action => {
        const iconName = {
          start: "start-indoors",
          sow: "direct-sow",
          transplant: "transplant"
        }[action];
        td.appendChild(icon(iconName));
      });
      row.appendChild(td);
    });
    return row;
  }

  const scheduleTable = document.getElementById("schedule");
  const tbody = document.createElement("tbody");
  clearElement(scheduleTable);
  scheduleTable.appendChild(createHeader(season));
  crops.forEach(crop => {
    tbody.appendChild(createCropRow(crop, schedule[crop.name]));
  });
  scheduleTable.appendChild(tbody);
}

function refreshInstructions(crops, season, schedule) {
  const instructionsDiv = document.getElementById("instructions");
  season.weeks.forEach(week => {
    const actions = crops.flatMap(crop => {
      const i = week.offset + WEEKS_BEFORE_LAST_FROST;
      return schedule[crop.name][i].actions.map(action => {
        return {
          crop: crop,
          type: action
        };
      });
    }).sort((a, b) => {
      if(a.type < b.type) {
        return -1;
      } else if(a.type > b.type) {
        return 1;
      }

      return 0;
    });;

    if(actions.length > 0) {
      const weekDiv = document.createElement("div");
      const heading = document.createElement("h3");
      heading.appendChild(document.createTextNode(monthAndDay(week.date)));
      weekDiv.appendChild(heading);
      actions.forEach(action => {
        const p = document.createElement("p");
        let prefix;
        let suffix;
        if(action.type == "start") {
          prefix = "Start ";
          suffix = " indoors.";
        } else if(action.type == "sow") {
          prefix = "Sow ";
          suffix = " outdoors.";
        } else if(action.type == "transplant") {
          prefix = "Transplant ";
          suffix = " outdoors.";
        }
        p.appendChild(document.createTextNode(prefix));
        p.appendChild(makeDetailLink(action.crop));
        p.appendChild(document.createTextNode(suffix));
        weekDiv.appendChild(p);
      });
      instructionsDiv.appendChild(weekDiv);
    }
  });
}

function refreshView() {
  function loadDate(name) {
    const dateString = window.localStorage.getItem(name);
    return dateString && new Date(Date.parse(dateString));
  }

  const lastFrostDate = loadDate("lastFrostDate");
  const firstFrostDate = loadDate("firstFrostDate");

  if(firstFrostDate && lastFrostDate) {
    const season = new Season(lastFrostDate, firstFrostDate);
    const schedule = makeSchedule(CROPS, season);
    refreshTable(CROPS, season, schedule);
    refreshInstructions(CROPS, season, schedule);
  }
}

function getLastFrostDateInput() {
  return document.querySelector("input[name='last-frost-date']");
}

function getFirstFrostDateInput() {
  return document.querySelector("input[name='first-frost-date']");
}

function loadConfiguration() {
  const lastFrostDate = window.localStorage.getItem("lastFrostDate");
  const firstFrostDate = window.localStorage.getItem("firstFrostDate");
  if(lastFrostDate) {
    getLastFrostDateInput().value = lastFrostDate;
  }
  if(firstFrostDate) {
    getFirstFrostDateInput().value = firstFrostDate;
  }
}

function loadIntensiveGarden() {
  loadConfiguration();
  getLastFrostDateInput().addEventListener("input", event => {
    window.localStorage.setItem("lastFrostDate", event.target.value);
    refreshView();
  });
  getFirstFrostDateInput().addEventListener("input", event => {
    window.localStorage.setItem("firstFrostDate", event.target.value);
    refreshView();
  });
  refreshView();
  // Open/close sections of page.
  document.querySelectorAll("section").forEach(section => {
    const container = section.querySelector(".section-container");
    const header = section.querySelector("h2");
    header.classList.add("open");
    header.addEventListener("click", event => {
      header.classList.remove(container.hidden ? "closed" : "open");
      container.hidden = !container.hidden;
      header.classList.add(container.hidden ? "closed" : "open");
    });
  });
}

window.addEventListener("load", loadIntensiveGarden);