init

2026-09-19 20:21:47 +02:00
commit 0798933b05
62 changed files with 7658 additions and 0 deletions
@@ -0,0 +1,145 @@
+// Package config holds tunable simulation parameters.
+//
+// Units used throughout the simulation: distance in kilometres, time in
+// seconds, mass in kilograms, force in newtons. Angles are radians.
+package config
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strconv"
+
+	"wh/fixed"
+)
+
+const SecondsPerDay = 86400
+
+type Config struct {
+	// Seed identifies the world. The same seed and inputs always produce the
+	// same simulation.
+	Seed uint64
+
+	// Time resolution.
+	TicksPerDay   int // must divide SecondsPerDay
+	CyclesPerTick int // VM instructions each ship may execute per tick
+
+	// Ship computer sizes.
+	ProgramBytes int // max program size
+	RAMBytes     int // data RAM, includes comm buffers
+	CommBytes    int // size of each of the uplink and downlink buffers
+
+	// World.
+	OrbitSpeed     fixed.F // km/s; speed of every circular orbit (star pulls with v^2/r)
+	AsteroidCount  int
+	BeltInner      fixed.F // km
+	BeltOuter      fixed.F // km
+	MaxInclination fixed.F // radians; asteroid inclinations are drawn up to this
+}
+
+func Default() Config {
+	return Config{
+		Seed:           1,
+		TicksPerDay:    1440,
+		CyclesPerTick:  2000,
+		ProgramBytes:   4096,
+		RAMBytes:       8192,
+		CommBytes:      1024,
+		OrbitSpeed:     fixed.FromInt(3),
+		AsteroidCount:  500,
+		BeltInner:      fixed.FromInt(1_500_000),
+		BeltOuter:      fixed.FromInt(3_000_000),
+		MaxInclination: fixed.FromRatio(1, 5), // ~11.5 degrees
+	}
+}
+
+// TickSeconds is the simulated duration of one tick.
+func (c Config) TickSeconds() int { return SecondsPerDay / c.TicksPerDay }
+
+func (c Config) Validate() error {
+	switch {
+	case c.TicksPerDay <= 0 || SecondsPerDay%c.TicksPerDay != 0:
+		return fmt.Errorf("TicksPerDay must divide %d, got %d", SecondsPerDay, c.TicksPerDay)
+	case c.CyclesPerTick <= 0:
+		return fmt.Errorf("CyclesPerTick must be positive")
+	case c.ProgramBytes <= 0 || c.ProgramBytes%4 != 0:
+		return fmt.Errorf("ProgramBytes must be a positive multiple of 4")
+	case c.CommBytes <= 0 || c.RAMBytes < 2*c.CommBytes:
+		return fmt.Errorf("RAMBytes must hold both comm buffers")
+	case c.MaxInclination < 0 || c.MaxInclination > fixed.HalfPi:
+		return fmt.Errorf("MaxInclination must be within [0, pi/2]")
+	case c.OrbitSpeed <= 0:
+		return fmt.Errorf("OrbitSpeed must be positive")
+	case c.BeltInner <= 0 || c.BeltOuter <= c.BeltInner:
+		return fmt.Errorf("invalid belt radii")
+	}
+	return nil
+}
+
+// Bind registers a flag for each tunable on fs and returns the config that
+// the flags will fill in when fs is parsed. Each tunable can also be set from
+// an environment variable (see EnvVars); a flag on the command line overrides
+// the environment. A malformed environment value is an error.
+func Bind(fs *flag.FlagSet) (*Config, error) {
+	c := Default()
+	if err := c.applyEnv(os.Getenv); err != nil {
+		return nil, err
+	}
+	fs.Uint64Var(&c.Seed, "seed", c.Seed, "world seed (env WH_SEED)")
+	fs.IntVar(&c.TicksPerDay, "ticks-per-day", c.TicksPerDay, "simulation ticks per day (env WH_TICKS_PER_DAY)")
+	fs.IntVar(&c.CyclesPerTick, "cycles-per-tick", c.CyclesPerTick, "VM cycles per ship per tick (env WH_CYCLES_PER_TICK)")
+	fs.IntVar(&c.ProgramBytes, "program-bytes", c.ProgramBytes, "max ship program size (env WH_PROGRAM_BYTES)")
+	fs.IntVar(&c.RAMBytes, "ram-bytes", c.RAMBytes, "ship RAM size (env WH_RAM_BYTES)")
+	fs.IntVar(&c.CommBytes, "comm-bytes", c.CommBytes, "uplink/downlink buffer size (env WH_COMM_BYTES)")
+	fs.IntVar(&c.AsteroidCount, "asteroids", c.AsteroidCount, "number of asteroids (env WH_ASTEROIDS)")
+	return &c, nil
+}
+
+// EnvVars lists the environment variables that set the world, for documentation.
+var EnvVars = []string{
+	"WH_SEED", "WH_TICKS_PER_DAY", "WH_CYCLES_PER_TICK", "WH_PROGRAM_BYTES",
+	"WH_RAM_BYTES", "WH_COMM_BYTES", "WH_ASTEROIDS",
+}
+
+func (c *Config) applyEnv(get func(string) string) error {
+	var err error
+	num := func(name string, dst any) {
+		v := get(name)
+		if v == "" || err != nil {
+			return
+		}
+		switch d := dst.(type) {
+		case *uint64:
+			var n uint64
+			if n, err = strconv.ParseUint(v, 10, 64); err == nil {
+				*d = n
+			}
+		case *int:
+			var n int
+			if n, err = strconv.Atoi(v); err == nil {
+				*d = n
+			}
+		}
+		if err != nil {
+			err = fmt.Errorf("%s=%q: %w", name, v, err)
+		}
+	}
+	num("WH_SEED", &c.Seed)
+	num("WH_TICKS_PER_DAY", &c.TicksPerDay)
+	num("WH_CYCLES_PER_TICK", &c.CyclesPerTick)
+	num("WH_PROGRAM_BYTES", &c.ProgramBytes)
+	num("WH_RAM_BYTES", &c.RAMBytes)
+	num("WH_COMM_BYTES", &c.CommBytes)
+	num("WH_ASTEROIDS", &c.AsteroidCount)
+	return err
+}
+
+// DatabaseURL returns the default database location: $DATABASE_URL if set,
+// else a SQLite file in the working directory. The -db flag overrides it.
+// Accepted forms are "sqlite:<path>" and "postgres://...".
+func DatabaseURL() string {
+	if v := os.Getenv("DATABASE_URL"); v != "" {
+		return v
+	}
+	return "sqlite:wh.db"
+}