Major stats upgrade.

StatLiteral: just emit a stat in the obvious way. Plus helper functions.

Can also identify stats via struct tags, no more Stored type!

Can also identify stat methods via name (with compatible types).

cardsim/stats.go

@@ -4,7 +4,11 @@ import (
 	"fmt"
 	"reflect"
 	"sort"
+	"strconv"
 	"strings"
+	"unicode"
+
+	"golang.org/x/exp/constraints"
 )
 
 // A StatsCollection contains stats.
@@ -114,9 +118,25 @@ func (s statFunc[T]) Visible() bool {
 	return s.visible
 }
 
-// ExtractStats pulls all exported Stat fields (not functions) out of a struct.
-// If x cannot be resolved to a struct, it panics. It unwraps interfaces and
-// follows pointers to try to find a struct.
+// ExtractStats pulls all exported stats out of a struct. It puts fields before
+// method.
+//
+// A field is a stat if it is of some Stat type or is tagged with `cardsim:"stat"`,
+// `cardsim:"hidden"` (invisible stat), `cardsim:"round2"` (or any integer, 2 is
+// just an example), or `cardsim:"hiddenround3"`. `hiddenstat`, `statround`, and
+// `hiddenstatround` are also accepted, but other orders of these directives
+// are not. A "round" stat must be a float type and it will be rounded to
+// this number of decimal places.
+//
+// A method is a Stat if it takes 0 arguments, returns exactly 1 value, and
+// starts with Stat or HiddenStat.
+//
+// The name of these inferred stats is calculated by breaking the name into
+// separate words before each capital letter, unless there are consecutive
+// capital letters, which it interprets as an initialism (followed by the
+// start of another word, if it's not at the end). To insert a space between
+// consecutive capital letters, insert an underscore (`_`). This name inference
+// trims "Stat" and "HiddenStat" off the front of method names.
 func ExtractStats(x any) []Stat {
 	v := reflect.ValueOf(x)
 	for k := v.Kind(); k == reflect.Pointer || k == reflect.Interface; k = v.Kind() {
@@ -125,18 +145,101 @@ func ExtractStats(x any) []Stat {
 	if v.Kind() != reflect.Struct {
 		panic(fmt.Errorf("%T is not a struct", x))
 	}
+	typ := v.Type()
 
 	var ret []Stat
-	lim := v.NumField()
-	for i := 0; i < lim; i++ {
-		f := v.Field(i)
+	fields := reflect.VisibleFields(typ)
+	for _, sf := range fields {
+		if !sf.IsExported() {
+			continue
+		}
+		f := v.FieldByIndex(sf.Index)
 		if !f.CanInterface() {
 			continue
 		}
-		x := f.Interface()
-		if s, ok := x.(Stat); ok {
+		if s, ok := f.Interface().(Stat); ok {
 			ret = append(ret, s)
+			continue
 		}
+		if t := sf.Tag.Get("cardsim"); t != "" {
+			isStat := false
+			isHidden := false
+			t = strings.ToLower(t)
+			t = strings.TrimSpace(t)
+			if strings.HasPrefix(t, "hidden") {
+				isStat = true
+				isHidden = true
+				t = t[6:]
+			}
+			if strings.HasPrefix(t, "stat") {
+				isStat = true
+				t = t[4:]
+			}
+			var val string
+			if strings.HasPrefix(t, "round") {
+				isStat = true
+				t = t[5:]
+				n, _ := strconv.Atoi(t)
+				fs := fmt.Sprintf("%%.%df", n)
+				val = fmt.Sprintf(fs, f.Interface())
+			} else if isStat {
+				val = fmt.Sprint(f.Interface())
+			} else {
+				continue // not identifiably a stat
+			}
+			ret = append(ret, &StatLiteral{
+				Name:      strings.Join(explode(sf.Name), " "),
+				Value:     val,
+				IsVisible: !isHidden,
+			})
+			continue
+		}
+		// Else, not a stat.
+	}
+
+	lim := typ.NumMethod()
+	for i := 0; i < lim; i++ {
+		m := typ.Method(i)
+		if !m.IsExported() {
+			continue
+		}
+		tm := m.Type
+		if tm.NumIn() != 1 {
+			// 1 arg -- receiver
+			continue
+		}
+		if tm.NumOut() != 1 {
+			continue
+		}
+		nameParts := explode(m.Name)
+		if len(nameParts) < 2 {
+			continue
+		}
+		isHidden := false
+		if nameParts[0] == "Hidden" {
+			isHidden = true
+			nameParts = nameParts[1:]
+		}
+		if nameParts[0] != "Stat" {
+			continue
+		}
+		n := strings.Join(nameParts[1:], ": ")
+		if n == "" {
+			continue
+		}
+		val := v.Method(i).Call([]reflect.Value{})
+		if len(val) != 1 {
+			// This shouldn't happen - we already checked Out. Weird.
+			continue
+		}
+		if !val[0].CanInterface() {
+			continue
+		}
+		ret = append(ret, &StatLiteral{
+			Name:      n,
+			Value:     fmt.Sprint(val[0].Interface()),
+			IsVisible: !isHidden,
+		})
 	}
 	return ret
 }
@@ -173,3 +276,105 @@ func (s statSorter) Less(i, j int) bool {
 	// Names differ only by capitalization, if that.
 	return lhs.StatName() < rhs.StatName()
 }
+
+// StatLiteral stores a ready-to-emit stat value.
+type StatLiteral struct {
+	Name      string
+	Value     string
+	IsVisible bool
+}
+
+func (s *StatLiteral) StatName() string {
+	return s.Name
+}
+
+func (s *StatLiteral) String() string {
+	return s.Value
+}
+
+func (s *StatLiteral) Visible() bool {
+	return s.IsVisible
+}
+
+func EmitStat(name string, v any) *StatLiteral {
+	return &StatLiteral{
+		Name:      name,
+		Value:     fmt.Sprint(v),
+		IsVisible: true,
+	}
+}
+
+func EmitHiddenStat(name string, v any) *StatLiteral {
+	return &StatLiteral{
+		Name:      name,
+		Value:     fmt.Sprint(v),
+		IsVisible: false,
+	}
+}
+
+func Statf(name string, f string, args ...any) *StatLiteral {
+	return &StatLiteral{
+		Name:      name,
+		Value:     fmt.Sprintf(f, args...),
+		IsVisible: true,
+	}
+}
+
+func HiddentStatf(name string, f string, args ...any) *StatLiteral {
+	return &StatLiteral{
+		Name:      name,
+		Value:     fmt.Sprintf(f, args...),
+		IsVisible: false,
+	}
+}
+
+func RoundStat[N constraints.Float](name string, val N, decimals int) *StatLiteral {
+	f := fmt.Sprintf("%%.%df", decimals)
+	return &StatLiteral{
+		Name:      name,
+		Value:     fmt.Sprintf(f, val),
+		IsVisible: true,
+	}
+}
+
+func RoundHiddenStat[N constraints.Float](name string, val N, decimals int) *StatLiteral {
+	r := RoundStat(name, val, decimals)
+	r.IsVisible = false
+	return r
+}
+
+// explode turns CamelCase into multiple strings. It recognizes initialisms. To
+// split consecutive capital letters into separate words instead of recognizing
+// them as an initialism, insert underscores.
+func explode(s string) []string {
+	var parts []string
+	started := 0
+	initialism := false
+	for i, r := range s {
+		if unicode.IsUpper(r) {
+			if initialism || (started == i) {
+				continue
+			}
+			if started == i-1 {
+				initialism = true
+				continue
+			}
+			parts = append(parts, s[started:i])
+			started = i
+			continue
+		}
+		if r == '_' {
+			parts = append(parts, s[started:i])
+			initialism = false
+			started = i + 1
+			continue
+		}
+		if initialism {
+			parts = append(parts, s[started:i-1])
+			initialism = false
+			started = i - 1
+		}
+	}
+	parts = append(parts, s[started:])
+	return parts
+}

go.mod

@@ -7,4 +7,5 @@ require github.com/kr/pretty v0.3.1
 require (
 	github.com/kr/text v0.2.0 // indirect
 	github.com/rogpeppe/go-internal v1.9.0 // indirect
+	golang.org/x/exp v0.0.0-20230321023759-10a507213a29
 )

go.sum

@@ -6,3 +6,5 @@ github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
 github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+golang.org/x/exp v0.0.0-20230321023759-10a507213a29 h1:ooxPy7fPvB4kwsA2h+iBNHkAbp/4JxTSwCmvdjEYmug=
+golang.org/x/exp v0.0.0-20230321023759-10a507213a29/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=

smoketest/collection.go

@@ -11,6 +11,10 @@ type SmokeTestCollection struct {
 	Turns  cardsim.Invisible[int]
 
 	Flavor cardsim.Stored[string]
+
+	Things       int     `cardsim:"stat"`
+	MoreThings   int     `cardsim:"hidden"`
+	FloatyThings float64 `cardsim:"round1"`
 }
 
 func (c *SmokeTestCollection) Average() float64 {
@@ -23,3 +27,7 @@ func (c *SmokeTestCollection) Stats() []cardsim.Stat {
 	cardsim.SortStats(stats)
 	return stats
 }
+
+func (c *SmokeTestCollection) StatTotalThings() float64 {
+	return float64(c.Things+c.MoreThings) + c.FloatyThings
+}