Initial commit: prognosis, the Go implementation

An hour-by-hour forecast for the terminal, with official IMGW warnings for
Polish locations. Replaces the Python version, whose cache file format it
keeps so the two can coexist until this reaches parity.

Open-Meteo provides the forecast, geocoding and pollen; GUGiK turns
coordinates into a TERYT powiat code; IMGW supplies the warnings, filtered
to that powiat rather than the whole country. Only the two lookups that
never change are cached. Forecasts never are.

Silence is never allowed to read as all-clear: "no warnings in force" and
"the check failed" are reported as distinct states.

Place names are resolved without guessing. A name matching several places
is refused with a numbered list carrying each candidate's region and
coordinates, and -pick N chooses one and remembers it. A stray positional
beside -l is an error, so an unquoted "Wiry, PL" cannot silently resolve to
somewhere else.

The cache is written one entry per line with sorted keys, and treated as
disposable but not worthless: an entry that will not parse is skipped and
the rest kept, and a file that will not parse at all is moved to
cache.json.bad rather than overwritten.

No third-party dependencies. `make ci` is the gate: gofmt clean, vet, tests.

1 files changed, 158 insertions, 0 deletions

diff --git a/internal/config/config_test.go b/internal/config/config_test.go
new file mode 100644
index 0000000..06c0234
--- /dev/null
+++ b/internal/config/config_test.go
@@ -0,0 +1,158 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func write(t *testing.T, body string) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "config")
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return path
+}
+
+func TestLoadMissingFileKeepsDefaults(t *testing.T) {
+	cfg, err := Load(filepath.Join(t.TempDir(), "absent"))
+	if err != nil {
+		t.Fatalf("missing file should not be an error: %v", err)
+	}
+	if cfg.Hours != 12 || cfg.Icons != "nerd" {
+		t.Fatalf("defaults not returned: %+v", cfg)
+	}
+}
+
+func TestLoadOverridesOnlyWhatIsSet(t *testing.T) {
+	cfg, err := Load(write(t, "hours=24\nicons=emoji\n"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.Hours != 24 {
+		t.Errorf("hours = %d, want 24", cfg.Hours)
+	}
+	if cfg.Icons != "emoji" {
+		t.Errorf("icons = %q, want emoji", cfg.Icons)
+	}
+	// Untouched keys must keep their defaults.
+	if cfg.GraphHeight != 5 || !cfg.Graph {
+		t.Errorf("unset keys lost their defaults: %+v", cfg)
+	}
+}
+
+func TestLoadCommentsAndBlanks(t *testing.T) {
+	cfg, err := Load(write(t, "\n# a comment\n\nhours=6   # trailing comment\n"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cfg.Hours != 6 {
+		t.Fatalf("hours = %d, want 6 (trailing comment must be stripped)", cfg.Hours)
+	}
+}
+
+func TestLoadErrors(t *testing.T) {
+	for name, body := range map[string]string{
+		"no equals":    "hours 12\n",
+		"unknown key":  "colour=always\n",
+		"not a number": "hours=soon\n",
+		"not a bool":   "graph=maybe\n",
+	} {
+		t.Run(name, func(t *testing.T) {
+			if _, err := Load(write(t, body)); err == nil {
+				t.Fatalf("expected an error for %q", body)
+			}
+		})
+	}
+}
+
+func TestPollenAllAndNone(t *testing.T) {
+	cfg, _ := Load(write(t, "pollen=all\n"))
+	if len(cfg.Pollen) != len(AllSpecies) {
+		t.Errorf("pollen=all gave %v", cfg.Pollen)
+	}
+	cfg, _ = Load(write(t, "pollen=none\n"))
+	if len(cfg.Pollen) != 0 {
+		t.Errorf("pollen=none gave %v", cfg.Pollen)
+	}
+}
+
+func TestValidateNamesTheOffender(t *testing.T) {
+	cfg := Default()
+	cfg.Columns = []string{"hour", "tempature"}
+	err := cfg.Validate()
+	if err == nil {
+		t.Fatal("expected an error for an unknown column")
+	}
+	if !strings.Contains(err.Error(), "tempature") {
+		t.Errorf("error must name the offending column, got: %v", err)
+	}
+	if !strings.Contains(err.Error(), "conditions") {
+		t.Errorf("error must list valid columns, got: %v", err)
+	}
+}
+
+func TestValidateRejectsBadEnums(t *testing.T) {
+	for name, mutate := range map[string]func(*Config){
+		"icons":        func(c *Config) { c.Icons = "pictures" },
+		"color":        func(c *Config) { c.Color = "sometimes" },
+		"units":        func(c *Config) { c.Units = "furlongs" },
+		"hours":        func(c *Config) { c.Hours = 0 },
+		"graph_height": func(c *Config) { c.GraphHeight = 1 },
+		"pollen":       func(c *Config) { c.Pollen = []string{"oak"} },
+	} {
+		t.Run(name, func(t *testing.T) {
+			cfg := Default()
+			mutate(&cfg)
+			if err := cfg.Validate(); err == nil {
+				t.Fatalf("expected %s to be rejected", name)
+			}
+		})
+	}
+}
+
+func TestDefaultIsValid(t *testing.T) {
+	if err := Default().Validate(); err != nil {
+		t.Fatalf("the built-in default must be valid: %v", err)
+	}
+}
+
+func TestFieldsRequestsOnlySelectedColumns(t *testing.T) {
+	cfg := Default()
+	cfg.Columns = []string{"hour", "temp", "wind"}
+	got := strings.Join(cfg.Fields(), ",")
+	want := "temperature_2m,wind_speed_10m"
+	if got != want {
+		t.Fatalf("Fields() = %q, want %q", got, want)
+	}
+}
+
+func TestFieldsDeduplicates(t *testing.T) {
+	cfg := Default()
+	// icon and conditions both come from weather_code.
+	cfg.Columns = []string{"icon", "conditions"}
+	if got := cfg.Fields(); len(got) != 1 || got[0] != "weather_code" {
+		t.Fatalf("Fields() = %v, want one weather_code", got)
+	}
+}
+
+func TestWriteDefaultRoundTrips(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "sub", "config")
+	want := Default()
+	want.Location = "Krakow"
+	if err := WriteDefault(path, want); err != nil {
+		t.Fatal(err)
+	}
+	got, err := Load(path)
+	if err != nil {
+		t.Fatalf("the file we generate must parse: %v", err)
+	}
+	if got.Location != "Krakow" || got.Hours != want.Hours || got.Icons != want.Icons {
+		t.Fatalf("round trip changed values:\n got %+v\nwant %+v", got, want)
+	}
+	if err := got.Validate(); err != nil {
+		t.Fatalf("the file we generate must validate: %v", err)
+	}
+}