package store

import (
	"strings"
	"testing"
	"testing/fstest"
)

// The refusals in this file are the ones that decide whether a schema can be trusted months
// later. Each has a wrong answer that looks helpful — skip it, apply it anyway, warn and carry on
// — and each of those turns "this database disagrees with these files" into a silence.

func load(t *testing.T, files fstest.MapFS) ([]Migration, error) {
	t.Helper()
	return LoadMigrations(files, "migrations")
}

func file(body string) *fstest.MapFile { return &fstest.MapFile{Data: []byte(body)} }

func TestMigrationsAreReadInNumericOrder(t *testing.T) {
	// Read from a directory, which has no order of its own. Alphabetical happens to agree with
	// numeric while the numbers are the same width, which is exactly why this is asserted rather
	// than assumed.
	got, err := load(t, fstest.MapFS{
		"migrations/0010-tenth.sql":  file("select 10"),
		"migrations/0002-second.sql": file("select 2"),
		"migrations/0001-first.sql":  file("select 1"),
	})
	if err != nil {
		t.Fatal(err)
	}
	var order []int
	for _, m := range got {
		order = append(order, m.Number)
	}
	if len(order) != 3 || order[0] != 1 || order[1] != 2 || order[2] != 10 {
		t.Errorf("migrations came back in order %v; they run in the order they are returned", order)
	}
}

func TestAMisnamedFileIsAnErrorRatherThanSkipped(t *testing.T) {
	// The tempting behaviour is to ignore anything that does not match, so that a README can sit
	// in the directory. The cost is that a migration named `001-thing.sql` or `0002_thing.sql` is
	// then ignored in silence, and the schema simply lacks it — surfacing later as a missing
	// column, a long way from the file that was misnamed.
	_, err := load(t, fstest.MapFS{
		"migrations/0001-first.sql":  file("select 1"),
		"migrations/0002_second.sql": file("select 2"),
	})
	if err == nil {
		t.Fatal("a misnamed migration was skipped silently; it would never run and nothing would say so")
	}
}

func TestTwoMigrationsWithOneNumberAreRefused(t *testing.T) {
	// Order is the entire guarantee. Two files with one number have none, and whichever the
	// filesystem returned first would win.
	_, err := load(t, fstest.MapFS{
		"migrations/0001-first.sql":      file("select 1"),
		"migrations/0001-also-first.sql": file("select 2"),
	})
	if err == nil {
		t.Fatal("two migrations numbered 0001 were accepted")
	}
}

func TestAnEmptyMigrationIsRefused(t *testing.T) {
	// An empty migration records that something happened and changes nothing — the one state that
	// cannot be told apart from a mistake, and it is recorded as done for ever.
	_, err := load(t, fstest.MapFS{"migrations/0001-nothing.sql": file("   \n\t\n")})
	if err == nil {
		t.Fatal("an empty migration was accepted")
	}
}

func TestAChangedMigrationIsRefused(t *testing.T) {
	// The one that matters most. The database holds what the old file said; the repository holds
	// the new one; nothing anywhere holds the difference. Applying it again would be wrong and
	// skipping it silently leaves the two permanently out of step.
	migrations := []Migration{{Number: 1, Name: "nodes", Checksum: "aaaa"}}
	applied := []Applied{{Number: 1, Name: "nodes", Checksum: "bbbb"}}

	_, err := Pending(migrations, applied)
	if err == nil {
		t.Fatal("a migration whose file changed after it ran was accepted")
	}
	if !strings.Contains(err.Error(), "0001-nodes") {
		t.Errorf("the refusal does not name the migration: %v", err)
	}
}

func TestAnUnchangedMigrationIsNotPending(t *testing.T) {
	// The other half, and the one that makes the run idempotent. Without it every start would
	// re-apply the whole schema.
	migrations := []Migration{{Number: 1, Name: "nodes", Checksum: "aaaa"}}
	applied := []Applied{{Number: 1, Name: "nodes", Checksum: "aaaa"}}

	pending, err := Pending(migrations, applied)
	if err != nil {
		t.Fatal(err)
	}
	if len(pending) != 0 {
		t.Errorf("an already-applied migration came back as pending; every start would re-run it")
	}
}

func TestAMigrationArrivingBelowTheHighWaterMarkIsRefused(t *testing.T) {
	// Two branches take the same next number; they merge in whatever order they landed. The file
	// is fine and applying it now would run the schema in an order nobody tested — which is the
	// same class of fault as applying them out of order deliberately, arriving by accident.
	migrations := []Migration{
		{Number: 1, Name: "nodes", Checksum: "aaaa"},
		{Number: 2, Name: "late", Checksum: "cccc"},
		{Number: 3, Name: "third", Checksum: "bbbb"},
	}
	applied := []Applied{
		{Number: 1, Name: "nodes", Checksum: "aaaa"},
		{Number: 3, Name: "third", Checksum: "bbbb"},
	}

	_, err := Pending(migrations, applied)
	if err == nil {
		t.Fatal("a migration numbered below one that already ran was applied out of order")
	}
	if !strings.Contains(err.Error(), "0002-late") {
		t.Errorf("the refusal does not name the migration: %v", err)
	}
}

func TestEveryDisagreementIsReportedNotOnlyTheFirst(t *testing.T) {
	// A person looking at this is deciding what to do about a schema. Being told one problem,
	// fixing it, and being told the next is how a single decision becomes four.
	migrations := []Migration{
		{Number: 1, Name: "one", Checksum: "aaaa"},
		{Number: 2, Name: "two", Checksum: "cccc"},
	}
	applied := []Applied{
		{Number: 1, Name: "one", Checksum: "changed"},
		{Number: 3, Name: "three", Checksum: "dddd"},
	}

	_, err := Pending(migrations, applied)
	if err == nil {
		t.Fatal("expected refusals")
	}
	if !strings.Contains(err.Error(), "0001-one") || !strings.Contains(err.Error(), "0002-two") {
		t.Errorf("only some problems were reported: %v", err)
	}
}

func TestAContextNameThatCannotBeADatabaseIsRefused(t *testing.T) {
	// The name becomes an environment variable and a database name. One that is valid in one and
	// not the other fails at bootstrap, on a machine with no mesh on it and nobody watching.
	//
	// Asserted on *which* refusal fired, not merely that one did. Open has a second reason to
	// fail a line later — no credential — and an unusable name would have produced an error
	// either way, so a test asking only "was there an error" passes with this check deleted.
	// It was written that way first and confirmed to defend nothing.
	for _, name := range []string{"", "Inventory", "my-context", "9lives", "drop table"} {
		_, err := Open(t.Context(), name)
		if err == nil {
			t.Errorf("%q was accepted as a context name", name)
			continue
		}
		if !strings.Contains(err.Error(), "not a usable context name") {
			t.Errorf("%q was refused for the wrong reason: %v", name, err)
		}
	}
}

func TestAContextWithoutItsCredentialIsRefused(t *testing.T) {
	// And the message has to say that reusing another context's connection is not the remedy,
	// because it is the obvious one and it is how ADR 0008 gets quietly undone.
	t.Setenv(Variable("inventory"), "")
	_, err := Open(t.Context(), "inventory")
	if err == nil {
		t.Fatal("a context with no credential opened a store")
	}
	if !strings.Contains(err.Error(), Variable("inventory")) {
		t.Errorf("the refusal does not name the variable that is missing: %v", err)
	}
}

func TestAMalformedConnectionStringIsNotQuotedBack(t *testing.T) {
	// The value carries a password. An error message that quotes what it could not parse puts it
	// into a log, on the one machine where the bootstrap output is being watched by a person.
	secret := "hunter2-this-must-not-appear"
	t.Setenv(Variable("inventory"), "postgres://user:"+secret+"@host:notaport/db")

	_, err := Open(t.Context(), "inventory")
	if err == nil {
		t.Fatal("a malformed connection string was accepted")
	}
	if strings.Contains(err.Error(), secret) {
		t.Errorf("the password appeared in the error: %v", err)
	}
}

func TestTheVariableAndDatabaseFollowTheContextName(t *testing.T) {
	if got := Variable("inventory"); got != "MESH_STORE_INVENTORY" {
		t.Errorf("Variable(inventory) = %q", got)
	}
	if got := Database("inventory"); got != "inventory" {
		t.Errorf("Database(inventory) = %q", got)
	}
}