Simplify projection table generation.

Instead of pre-allocating the grid and using tricky indexing to fill in
the cells, just fully regenerate it. But do it columnwise first, and
then transpose it.

moon/moon.go

@@ -2,6 +2,7 @@ package moon
 
 import (
 	"context"
+	"fmt"
 	"math"
 	"time"
 
@@ -14,6 +15,7 @@ type Math struct {
 	CurrentPrice coindesk.Price
 	Columns      []Column
 	Goals        []Goal
+	Labels       []string
 }
 
 func NewMath(asset coindesk.Asset, goals []Goal, bases []Base) (m Math) {
@@ -22,10 +24,14 @@ func NewMath(asset coindesk.Asset, goals []Goal, bases []Base) (m Math) {
 	}
 	m.Asset = asset
 	m.Goals = goals
+	m.Labels = []string{"Starting", "CDPR"}
 	m.Columns = make([]Column, len(bases))
 	for i := range bases {
 		m.Columns[i].Base = bases[i]
 	}
+	for i := range goals {
+		m.Labels = append(m.Labels, goals[i].Name)
+	}
 	return
 }
 
@@ -106,6 +112,25 @@ type Column struct {
 	Projections   Projection
 }
 
+func (c *Column) Column() (entries []string) {
+	entries = append(entries, fmt.Sprintf("$%.2f", c.StartingPrice))
+	entries = append(entries, fmt.Sprintf("%.2f%%", (c.CDPR-1)*100))
+	never := c.CDPR <= 1
+	for i := range c.Projections.Dates {
+		var cell string
+		if never {
+			cell = "NEVER!!!!!"
+		} else {
+			cell = c.
+				Projections.
+				Dates[i].
+				Format("2006-01-02")
+		}
+		entries = append(entries, cell)
+	}
+	return
+}
+
 var DefaultGoals = []Goal{
 	{"$100k", 100000},
 	{"$150k", 150000},

tui/tui.go

@@ -49,19 +49,9 @@ func New(cfg config.Data) Model {
 			Width: 10,
 		})
 	}
-	projectionRows := make([]table.Row, len(math.Goals)+2)
-	for i := range projectionRows {
-		projectionRows[i] = make(table.Row, len(projectionCols))
-	}
-	projectionRows[0][0] = "Starting"
-	projectionRows[1][0] = "CDPR"
-	for i := range math.Goals {
-		projectionRows[i+2][0] = math.Goals[i].Name
-	}
 	projections := table.New(
 		table.WithColumns(projectionCols),
-		table.WithRows(projectionRows),
-		table.WithHeight(len(math.Goals)+2),
+		table.WithHeight(len(math.Labels)),
 		table.WithStyles(tableStyle),
 	)
 
@@ -106,30 +96,27 @@ func refillPrice(m *Model) {
 }
 
 func refillProjections(m *Model) {
-	rows := m.projections.Rows()
+	rows := []table.Row{m.math.Labels}
+	for i := range m.math.Columns {
+		rows = append(rows, m.math.Columns[i].Column())
+	}
+	rows = transpose(rows)
+	m.projections.SetRows(rows)
+}
 
-	for col := range m.math.Columns {
-		_ = col
-		never := false
-		if m.math.Columns[col].CDPR <= 1 {
-			never = true
-		}
-
-		rows[0][col+1] = fmt.Sprintf("$%.2f", m.math.Columns[col].StartingPrice)
-		rows[1][col+1] = fmt.Sprintf("%.2f%%", (m.math.Columns[col].CDPR-1)*100)
-		for row := 0; row < len(m.math.Goals); row++ {
-			var cell string
-			if never {
-				cell = "NEVER!!!!!"
-			} else {
-				cell = m.math.Columns[col].
-					Projections.Dates[row].
-					Format("2006-01-02")
-			}
-			rows[row+2][col+1] = cell
+func transpose(slice []table.Row) []table.Row {
+	xl := len(slice[0])
+	yl := len(slice)
+	result := make([]table.Row, xl)
+	for i := range result {
+		result[i] = make(table.Row, yl)
+	}
+	for i := 0; i < xl; i++ {
+		for j := 0; j < yl; j++ {
+			result[i][j] = slice[j][i]
 		}
 	}
-	m.projections.SetRows(rows)
+	return result
 }
 
 func (m Model) View() string {