118 lines
3.5 KiB
Go
118 lines
3.5 KiB
Go
package mujica
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import (
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"fmt"
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"math"
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"sort"
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"time"
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)
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// Candle is one period of trading: open, high, low, close and volume.
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type Candle struct {
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Time time.Time
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Open, High, Low, Close float64
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Volume float64
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}
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// marketCheckCandles panics on candles out of time order or with impossible prices.
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func marketCheckCandles(candles []Candle) {
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for i, c := range candles {
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if c.Time.IsZero() || i > 0 && !c.Time.After(candles[i-1].Time) {
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panic(fmt.Sprintf("mujica: candle %d time is zero or not after the one before", i))
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}
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if !(c.Low <= min(c.Open, c.Close)) || !(c.High >= max(c.Open, c.Close)) || c.Volume < 0 || math.IsNaN(c.Volume) {
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panic(fmt.Sprintf("mujica: candle %d has impossible prices or volume", i))
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}
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}
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}
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// MarketView is the caller-held window of a market chart: zoom and pan.
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type MarketView struct {
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// Count is how many candles show; zero shows 120.
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Count int
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// End is one past the last shown candle; zero follows the newest.
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End int
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}
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// marketWindow resolves the view to [from, to) over n candles, at most room wide.
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func marketWindow(v MarketView, n, room int) (from, to int) {
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if v.Count < 0 || v.End < 0 {
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panic("mujica: MarketView Count and End must not be negative")
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}
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count := v.Count
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if count == 0 {
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count = 120
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}
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count = max(1, min(count, room, n))
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to = n
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if v.End > 0 && v.End < n {
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to = max(v.End, count)
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}
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return to - count, to
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}
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// marketPan moves the view by delta candles; reaching the newest follows it again.
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func marketPan(v *MarketView, n, room, delta int) {
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from, to := marketWindow(*v, n, room)
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v.Count = to - from
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to = max(v.Count, min(n, to+delta))
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if to >= n {
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v.End = 0
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} else {
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v.End = to
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}
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}
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// marketZoom scales the shown count by f, keeping the newest shown candle, within 10 and room.
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func marketZoom(v *MarketView, n, room int, f float64) {
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from, to := marketWindow(*v, n, room)
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count := int(math.Round(float64(to-from) * f))
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if f > 1 && count == to-from {
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count++
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}
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v.Count = max(min(10, n), min(count, room, n))
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if to < n {
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v.End = max(to, v.Count)
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}
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}
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// marketIndexAt finds the candle at or before t, or -1 before the first.
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func marketIndexAt(candles []Candle, t time.Time) int {
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return sort.Search(len(candles), func(i int) bool { return candles[i].Time.After(t) }) - 1
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}
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// Interval names a candle period: 1m 3m 5m 15m 30m 1h 2h 4h 6h 12h 1D 3D 1W 1M.
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type Interval string
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// Intervals lists every Interval, shortest first.
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var Intervals = []Interval{"1m", "3m", "5m", "15m", "30m", "1h", "2h", "4h", "6h", "12h", "1D", "3D", "1W", "1M"}
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// Close returns when the candle holding t closes: periods align to the clock in loc, weeks start Monday.
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func (iv Interval) Close(t time.Time, loc *time.Location) time.Time {
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t = t.In(loc)
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day := time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, loc)
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step := func(d time.Duration) time.Time {
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since := t.Sub(day)
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return day.Add((since/d + 1) * d)
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}
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switch iv {
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case "1m", "3m", "5m", "15m", "30m":
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m, _ := time.ParseDuration(string(iv))
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return step(m)
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case "1h", "2h", "4h", "6h", "12h":
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h, _ := time.ParseDuration(string(iv))
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return step(h)
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case "1D":
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return day.AddDate(0, 0, 1)
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case "3D":
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days := int(day.Sub(time.Date(1970, 1, 1, 0, 0, 0, 0, loc)).Hours()/24 + 0.5)
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return day.AddDate(0, 0, 3-days%3)
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case "1W":
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back := (int(day.Weekday()) + 6) % 7
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return day.AddDate(0, 0, 7-back)
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case "1M":
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return time.Date(t.Year(), t.Month()+1, 1, 0, 0, 0, 0, loc)
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}
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panic(fmt.Sprintf("mujica: unknown Interval %q", string(iv)))
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}
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