package buildstep

import (
	"strings"
	"testing"
)

// The shared warm caches are read under a throwaway writable layer (novox/hq ADR 0448; issue 1309): a candidate's step
// writes into them as a build does, and nothing it writes outlives it or reaches a later build; only a trunk build
// writes them.
func TestACandidatesStepWritesTheCachesOnlyIntoAThrowawayLayer(t *testing.T) {
	fixedSystem(t)
	iso := Isolation{Workspace: "/w", Caches: []string{"/var/cache/go-build", "/var/cache/npm"}}
	argv, err := iso.Command("go", "test")
	if err != nil {
		t.Fatal(err)
	}
	for _, c := range iso.Caches {
		if !holds(argv, "--overlay-src", c, "--tmp-overlay", c) {
			t.Errorf("the cache %s is not under a throwaway layer: %v", c, argv)
		}
		if holds(argv, "--bind", c, c) {
			t.Errorf("a candidate's step writes the cache %s: %v", c, argv)
		}
	}
	iso.WriteCaches = true
	argv, _ = iso.Command("go", "build")
	for _, c := range iso.Caches {
		if !holds(argv, "--bind", c, c) || holds(argv, "--tmp-overlay", c) {
			t.Errorf("a trunk build does not write the cache %s: %v", c, argv)
		}
	}
	// 1921/S2: with a cache layer, a command reads the ask's kept layer above the shared cache and writes into a layer
	// on disk of the ask's own, never into the shared cache and never into a throwaway tmpfs.
	iso = Isolation{Workspace: "/w", Caches: []string{"/cache/gomod", "/cache/gobuild"}, CacheLayer: "/w/cachelayer"}
	argv, err = iso.Command("go", "vet")
	if err != nil {
		t.Fatal(err)
	}
	for i, c := range iso.Caches {
		if !holds(argv, "--overlay-src", c, "--overlay-src", keptLayer(iso.CacheLayer, i), "--overlay") {
			t.Errorf("the cache %s is not read beneath the ask's kept layer: %v", c, argv)
		}
		if up := overlayOf(argv, c); up == "" || !strings.HasPrefix(up, "/w/cachelayer/") {
			t.Errorf("the cache %s is written into %q, not a layer of the ask's own: %v", c, up, argv)
		}
		if holds(argv, "--tmp-overlay", c) || holds(argv, "--bind", c, c) {
			t.Errorf("the cache %s is thrown away or written: %v", c, argv)
		}
	}
	if _, err := (Isolation{Workspace: "/w", CacheLayer: "cachelayer"}).Command("go"); err == nil {
		t.Error("a relative cache layer was taken")
	}
}

// overlayOf answers the upper directory a command line gives the cache c, "" when it gives none.
func overlayOf(argv []string, c string) string {
	for i := 0; i+3 < len(argv); i++ {
		if argv[i] == "--overlay" && argv[i+3] == c {
			return argv[i+1]
		}
	}
	return ""
}