v0.14.0 web replay UI, My games, CLI replay

internal/client/replay/replay.go

@@ -0,0 +1,175 @@
+// Package replay steps through a stored game's history in the terminal
+// client. The state is separate from the live session: it holds the
+// history the server returned and a ply, and renders positions from the
+// stored FENs; it never computes a move.
+package replay
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/lixenwraith/chess/internal/client/api"
+)
+
+// State is a stored game and the ply shown: 0 is the initial position,
+// Len() the position after the last move.
+type State struct {
+	History *api.GameHistoryResponse
+	Ply     int
+}
+
+// New starts a replay at the initial position.
+func New(history *api.GameHistoryResponse) *State {
+	return &State{History: history}
+}
+
+// Len is the number of stored plies.
+func (s *State) Len() int { return len(s.History.Moves) }
+
+// Goto shows the position after ply plies, clamped to the stored line, and
+// returns the ply shown.
+func (s *State) Goto(ply int) int {
+	if ply < 0 {
+		ply = 0
+	}
+	if ply > s.Len() {
+		ply = s.Len()
+	}
+	s.Ply = ply
+	return s.Ply
+}
+
+func (s *State) Next() int  { return s.Goto(s.Ply + 1) }
+func (s *State) Prev() int  { return s.Goto(s.Ply - 1) }
+func (s *State) First() int { return s.Goto(0) }
+func (s *State) Last() int  { return s.Goto(s.Len()) }
+
+// AtEnd reports whether the last stored position is shown.
+func (s *State) AtEnd() bool { return s.Ply >= s.Len() }
+
+// FEN is the stored position at the current ply.
+func (s *State) FEN() string {
+	if s.Ply == 0 {
+		return s.History.InitialFEN
+	}
+	return s.History.Moves[s.Ply-1].FENAfterMove
+}
+
+// Move is the ply-th move (from 1), or nil for the initial position.
+func (s *State) Move(ply int) *api.HistoryMove {
+	if ply < 1 || ply > s.Len() {
+		return nil
+	}
+	return &s.History.Moves[ply-1]
+}
+
+// startsWithBlack and firstMoveNumber come from the initial FEN, so a game
+// from a custom position numbers its moves as its PGN does.
+func (s *State) start() (number int, black bool) {
+	parts := strings.Fields(s.History.InitialFEN)
+	number = 1
+	if len(parts) >= 6 {
+		if n, err := strconv.Atoi(parts[5]); err == nil && n > 0 {
+			number = n
+		}
+	}
+	black = len(parts) >= 2 && parts[1] == "b"
+	return number, black
+}
+
+// Label names a ply in PGN style: "2. Nf3", "2... Nf6", or "start".
+func (s *State) Label(ply int) string {
+	move := s.Move(ply)
+	if move == nil {
+		return "start"
+	}
+	first, black := s.start()
+	offset := ply - 1
+	if black {
+		offset++
+	}
+	number := first + offset/2
+	text := move.SAN
+	if text == "" {
+		text = move.MoveUCI
+	}
+	if move.PlayerColor == "b" {
+		return fmt.Sprintf("%d... %s", number, text)
+	}
+	return fmt.Sprintf("%d. %s", number, text)
+}
+
+// Movetext lists the moves with numbers, the current ply in brackets,
+// wrapped at width columns (80 when width is not positive).
+func (s *State) Movetext(width int) string {
+	if width <= 0 {
+		width = 80
+	}
+	first, black := s.start()
+	var tokens []string
+	number := first
+	for i, move := range s.History.Moves {
+		text := move.SAN
+		if text == "" {
+			text = move.MoveUCI
+		}
+		if i+1 == s.Ply {
+			text = "[" + text + "]"
+		}
+		switch {
+		case i == 0 && black:
+			tokens = append(tokens, fmt.Sprintf("%d...", number), text)
+			number++
+		case move.PlayerColor == "w":
+			tokens = append(tokens, fmt.Sprintf("%d.", number), text)
+		default:
+			tokens = append(tokens, text)
+			number++
+		}
+	}
+	if len(tokens) == 0 {
+		return "(no moves)"
+	}
+	var b strings.Builder
+	col := 0
+	for _, token := range tokens {
+		if col > 0 && col+1+len(token) > width {
+			b.WriteByte('\n')
+			col = 0
+		} else if col > 0 {
+			b.WriteByte(' ')
+			col++
+		}
+		b.WriteString(token)
+		col += len(token)
+	}
+	return b.String()
+}
+
+// Players names the sides: the stored name, the engine and level, or
+// "Anonymous".
+func (s *State) Players() (white, black string) {
+	return playerLabel(s.History.Players.White), playerLabel(s.History.Players.Black)
+}
+
+func playerLabel(p api.PlayerInfo) string {
+	switch {
+	case p.Type == 2:
+		return fmt.Sprintf("Stockfish L%d", p.Level)
+	case p.Name != "":
+		return p.Name
+	}
+	return "Anonymous"
+}
+
+// Result describes the outcome: "1-0 (checkmate)" or "ongoing".
+func (s *State) Result() string {
+	if s.History.Result == "" {
+		return "ongoing"
+	}
+	if s.History.Termination != "" {
+		return fmt.Sprintf("%s (%s)", s.History.PGNResult, strings.ReplaceAll(s.History.Termination, "_", " "))
+	}
+	return s.History.PGNResult
+}