feat(cli): mantle init connection recovery & Docker auto-provisioning (#7)

docs/superpowers/specs/2026-03-24-init-connection-recovery-design.md

@@ -0,0 +1,174 @@
+# `mantle init` Connection Recovery & Quickstart Fix
+
+**Date:** 2026-03-24
+**Issue:** [#7 — Get Running in 5 Minutes](https://github.com/dvflw/mantle/issues/7)
+**Status:** Draft
+
+## Problem
+
+The landing page quickstart tells users to run `docker compose up -d` after installing via `go install`. There's no `docker-compose.yml` when you install that way — step 2 immediately fails. The `mantle init` command needs to handle the "no database yet" case gracefully.
+
+## Design
+
+### Connection Recovery Flow
+
+`mantle init` already loads config and calls `db.Open`. The change adds a recovery path when the connection fails:
+
+```
+mantle init
+  ├─ db.Open succeeds → run migrations → done
+  └─ db.Open fails
+       ├─ host is NOT loopback → print error with details, offer [R]etry or [Q]uit
+       └─ host IS loopback → offer Docker auto-provisioning
+            ├─ user accepts
+            │    ├─ docker available → start container, wait for ready, run migrations → done
+            │    └─ docker unavailable → show message, offer [R]etry or [C]onnection string
+            └─ user declines → offer [R]etry or [C]onnection string
+```
+
+### Loopback Detection
+
+Parse the host from the configured database URL. Treat as loopback if the host is:
+- `localhost`
+- `127.0.0.1`
+- `::1`
+
+Use `net/url` to parse the connection string and extract the host.
+
+### Docker Auto-Provisioning
+
+When the user accepts Docker provisioning:
+
+1. Check Docker availability: exec `docker info` and check exit code
+2. Run the container:
+   ```
+   docker run -d \
+     --name mantle-postgres \
+     -p 5432:5432 \
+     -e POSTGRES_USER=mantle \
+     -e POSTGRES_PASSWORD=mantle \
+     -e POSTGRES_DB=mantle \
+     -v mantle-pgdata:/var/lib/postgresql/data \
+     postgres:16-alpine
+   ```
+3. Wait for readiness: poll `db.Open` with backoff (up to ~15s)
+4. On success: continue to migrations
+5. On timeout: error with "Container started but Postgres isn't accepting connections"
+
+Use `os/exec` to run Docker commands. The container config matches the existing defaults in `config.go` so no config persistence is needed.
+
+If the container name `mantle-postgres` already exists (stopped), remove it first and start fresh. If it's already running, skip straight to the readiness check.
+
+### Fallback: No Docker / User Declined
+
+Present two options:
+```
+Can't auto-provision — Docker isn't installed or isn't running.
+
+  [R] Retry (install or start Docker first)
+  [C] Enter a Postgres connection string
+
+Choice [R/c]:
+```
+
+- **Retry**: loop back to Docker availability check
+- **Connection string**: prompt for URL, validate with `db.Open`, on success continue to migrations, on failure show the error and re-prompt
+
+### Non-Loopback Failure
+
+When the configured URL points to a remote host and the connection fails:
+```
+Failed to connect to database at db.example.com:5432
+
+  Error: connection refused
+
+  [R] Retry (fix the issue and try again)
+  [Q] Quit
+
+Choice [R/q]:
+```
+
+Include the underlying error from `db.Open` (timeout, auth failure, TLS, DNS resolution, etc.) so the user can diagnose without guessing.
+
+- **Retry**: re-reads the config (picks up env var or config file changes made while waiting) and retries `db.Open`. This lets the user fix a typo, adjust a firewall rule, or start their database without restarting `mantle init`.
+- **Quit**: exit 1
+
+### Interactive Input
+
+Follow the existing pattern from `login.go`: use `fmt.Fscanln(cmd.InOrStdin(), &input)` for prompts. No new dependencies needed.
+
+When stdin is not a terminal (piped input, CI), skip all interactive prompts and return the connection error directly. Detect with `os.Stdin.Stat()` checking for `ModeCharDevice`.
+
+## Constant Extraction
+
+Before implementing the new init flow, extract shared constants that are currently duplicated across the codebase. This keeps the new code referencing a single source of truth.
+
+### `internal/dbdefaults/dbdefaults.go` — shared database & Docker defaults
+
+| Constant | Value | Current duplication |
+|----------|-------|---------------------|
+| `PostgresImage` | `"postgres:16-alpine"` | 7 test files + docker-compose.yml |
+| `TestUser` | `"mantle"` | 6 testcontainers setups |
+| `TestPassword` | `"mantle"` | 6 testcontainers setups |
+| `TestDatabase` | `"mantle_test"` | 6 testcontainers setups |
+| `ContainerName` | `"mantle-postgres"` | new (Docker provisioning) |
+
+### `internal/netutil/loopback.go` — loopback detection
+
+| Function/Const | Purpose | Current duplication |
+|----------------|---------|---------------------|
+| `IsLoopback(host string) bool` | Returns true for localhost, 127.0.0.1, ::1 | config.go SSL warning + new init.go recovery |
+
+### `internal/budget/budget.go` — reset mode constants
+
+| Constant | Value | Current duplication |
+|----------|-------|---------------------|
+| `ResetModeCalendar` | `"calendar"` | config.go validation + budget logic + tests |
+| `ResetModeRolling` | `"rolling"` | config.go validation + budget logic + tests |
+
+These already live in the budget package conceptually; just promote the string literals to exported constants.
+
+## Files Changed
+
+### Modified
+
+| File | Change |
+|------|--------|
+| `internal/cli/init.go` | Add connection recovery flow, Docker provisioning, interactive prompts |
+| `internal/config/config.go` | Use `netutil.IsLoopback` for SSL warning, use `budget.ResetMode*` constants |
+| `internal/budget/budget.go` | Add `ResetModeCalendar` / `ResetModeRolling` constants, use them in existing logic |
+| `internal/auth/auth_test.go` | Use `dbdefaults` constants for testcontainers setup |
+| `internal/workflow/store_test.go` | Use `dbdefaults` constants |
+| `internal/db/migrate_test.go` | Use `dbdefaults` constants |
+| `internal/secret/store_test.go` | Use `dbdefaults` constants |
+| `internal/engine/test_helpers_test.go` | Use `dbdefaults` constants |
+| `internal/budget/store_test.go` | Use `dbdefaults` constants |
+| `internal/connector/postgres_test.go` | Use `dbdefaults.PostgresImage` |
+| `site/src/components/GetStarted.astro` | Remove `docker compose up -d` from step 2, simplify to just `mantle init` |
+| `site/src/content/docs/getting-started/index.md` | Update quickstart to remove Docker prerequisite, explain `mantle init` handles DB setup |
+
+### New
+
+| File | Purpose |
+|------|---------|
+| `internal/dbdefaults/dbdefaults.go` | Shared Postgres image, test credentials, container name constants |
+| `internal/netutil/loopback.go` | `IsLoopback` function for host classification |
+| `internal/netutil/loopback_test.go` | Tests for loopback detection |
+| `internal/cli/docker.go` | Docker availability check, container start, readiness polling |
+| `internal/cli/init_test.go` | Tests for connection recovery flow, non-interactive fallback |
+| `internal/cli/docker_test.go` | Tests for Docker command construction, container name conflict handling |
+
+## Non-Goals
+
+- **Config file generation**: `mantle init` does not create `mantle.yaml`. The defaults work with the Docker container.
+- **Docker Compose**: we use `docker run`, not `docker compose`. No dependency on a compose file.
+- **Custom port/user/password in Docker flow**: always matches defaults. Users who need custom config can use the connection string prompt.
+- **Container lifecycle management**: `mantle init` starts the container; it doesn't stop or remove it. Users manage that themselves.
+
+## Testing Strategy
+
+- **Loopback detection**: unit test `isLoopback` with localhost, 127.0.0.1, ::1, remote hosts, IPv6
+- **Non-interactive detection**: unit test that piped stdin skips prompts and returns error
+- **Docker command construction**: verify the exact `docker run` args match defaults
+- **Integration**: testcontainers already covers the migration path; the new code paths are the interactive/Docker shell-out portions which are unit-tested with mocked exec
+- **Site content**: manual verification that quickstart steps are accurate

internal/auth/auth_test.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/dvflw/mantle/internal/config"
 	"github.com/dvflw/mantle/internal/db"
+	"github.com/dvflw/mantle/internal/dbdefaults"
 	"github.com/golang-jwt/jwt/v5"
 	"github.com/testcontainers/testcontainers-go"
 	"github.com/testcontainers/testcontainers-go/modules/postgres"
@@ -20,10 +21,10 @@ func setupTestStore(t *testing.T) *Store {
 	t.Helper()
 	ctx := context.Background()
 	pgContainer, err := postgres.Run(ctx,
-		"postgres:16-alpine",
-		postgres.WithDatabase("mantle_test"),
-		postgres.WithUsername("mantle"),
-		postgres.WithPassword("mantle"),
+		dbdefaults.PostgresImage,
+		postgres.WithDatabase(dbdefaults.TestDatabase),
+		postgres.WithUsername(dbdefaults.User),
+		postgres.WithPassword(dbdefaults.Password),
 		testcontainers.WithWaitStrategy(
 			wait.ForLog("database system is ready to accept connections").
 				WithOccurrence(2).

internal/budget/budget.go

@@ -6,12 +6,18 @@ import (
 	"time"
 )
 
+// Reset mode constants for budget period calculation.
+const (
+	ResetModeCalendar = "calendar"
+	ResetModeRolling  = "rolling"
+)
+
 // CurrentPeriodStart returns the start date of the current budget period.
 // For "calendar" mode: first day of the current month.
 // For "rolling" mode: the most recent occurrence of resetDay (1-28).
 func CurrentPeriodStart(now time.Time, mode string, resetDay int) time.Time {
 	now = now.UTC()
-	if mode == "rolling" && resetDay >= 1 && resetDay <= 28 {
+	if mode == ResetModeRolling && resetDay >= 1 && resetDay <= 28 {
 		if now.Day() >= resetDay {
 			return time.Date(now.Year(), now.Month(), resetDay, 0, 0, 0, 0, time.UTC)
 		}

internal/budget/store_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/dvflw/mantle/internal/budget"
 	"github.com/dvflw/mantle/internal/config"
 	"github.com/dvflw/mantle/internal/db"
+	"github.com/dvflw/mantle/internal/dbdefaults"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"github.com/testcontainers/testcontainers-go"
@@ -20,10 +21,10 @@ func setupTestDB(t *testing.T) *sql.DB {
 	t.Helper()
 	ctx := context.Background()
 	pgContainer, err := postgres.Run(ctx,
-		"postgres:16-alpine",
-		postgres.WithDatabase("mantle_test"),
-		postgres.WithUsername("mantle"),
-		postgres.WithPassword("mantle"),
+		dbdefaults.PostgresImage,
+		postgres.WithDatabase(dbdefaults.TestDatabase),
+		postgres.WithUsername(dbdefaults.User),
+		postgres.WithPassword(dbdefaults.Password),
 		testcontainers.WithWaitStrategy(
 			wait.ForLog("database system is ready to accept connections").
 				WithOccurrence(2).

internal/cli/docker.go

@@ -0,0 +1,106 @@
+package cli
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"os/exec"
+	"strings"
+	"time"
+
+	"github.com/dvflw/mantle/internal/config"
+	"github.com/dvflw/mantle/internal/db"
+	"github.com/dvflw/mantle/internal/dbdefaults"
+)
+
+// dockerRunArgs returns the arguments for `docker run` to start a Postgres
+// container matching Mantle's default configuration.
+func dockerRunArgs() []string {
+	return []string{
+		"run", "-d",
+		"--name", dbdefaults.ContainerName,
+		"-p", "5432:5432",
+		"-e", "POSTGRES_USER=" + dbdefaults.User,
+		"-e", "POSTGRES_PASSWORD=" + dbdefaults.Password,
+		"-e", "POSTGRES_DB=" + dbdefaults.Database,
+		"-v", "mantle-pgdata:/var/lib/postgresql/data",
+		dbdefaults.PostgresImage,
+	}
+}
+
+// parseHostFromURL extracts the hostname from a Postgres connection URL.
+func parseHostFromURL(rawURL string) string {
+	if rawURL == "" {
+		return ""
+	}
+	parsed, err := url.Parse(rawURL)
+	if err != nil {
+		return ""
+	}
+	return parsed.Hostname()
+}
+
+// dockerAvailable checks whether the Docker CLI is installed and the daemon is responsive.
+func dockerAvailable() bool {
+	cmd := exec.Command("docker", "info")
+	return cmd.Run() == nil
+}
+
+// dockerContainerStatus returns "running", "exited", or "" (not found)
+// for the mantle-postgres container.
+func dockerContainerStatus() string {
+	out, err := exec.Command("docker", "inspect", "-f", "{{.State.Status}}", dbdefaults.ContainerName).Output()
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(out))
+}
+
+// dockerRemoveContainer removes the mantle-postgres container (stopped or otherwise).
+func dockerRemoveContainer() error {
+	return exec.Command("docker", "rm", "-f", dbdefaults.ContainerName).Run()
+}
+
+// dockerStartPostgres starts a new Postgres container and waits for it to accept connections.
+func dockerStartPostgres(cfg config.DatabaseConfig) error {
+	// Handle existing container.
+	switch dockerContainerStatus() {
+	case "running":
+		// Already running — just wait for readiness.
+		return waitForPostgres(cfg)
+	case "exited", "created", "dead":
+		_ = dockerRemoveContainer()
+	}
+
+	args := dockerRunArgs()
+	out, err := exec.Command("docker", args...).CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("docker run failed: %w\n%s", err, string(out))
+	}
+
+	return waitForPostgres(cfg)
+}
+
+// waitForPostgres polls db.Open with backoff until the database accepts connections
+// or the timeout (~15s) is exceeded.
+func waitForPostgres(cfg config.DatabaseConfig) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+
+	delay := 500 * time.Millisecond
+	for {
+		database, err := db.Open(cfg)
+		if err == nil {
+			database.Close()
+			return nil
+		}
+		select {
+		case <-ctx.Done():
+			return fmt.Errorf("container started but Postgres isn't accepting connections after 15s: %w", err)
+		case <-time.After(delay):
+			if delay < 2*time.Second {
+				delay *= 2
+			}
+		}
+	}
+}

internal/cli/docker_test.go

@@ -0,0 +1,41 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDockerRunArgs(t *testing.T) {
+	args := dockerRunArgs()
+	assert.Equal(t, []string{
+		"run", "-d",
+		"--name", "mantle-postgres",
+		"-p", "5432:5432",
+		"-e", "POSTGRES_USER=mantle",
+		"-e", "POSTGRES_PASSWORD=mantle",
+		"-e", "POSTGRES_DB=mantle",
+		"-v", "mantle-pgdata:/var/lib/postgresql/data",
+		"postgres:16-alpine",
+	}, args)
+}
+
+func TestParseHostFromURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		url      string
+		expected string
+	}{
+		{"standard", "postgres://mantle:mantle@localhost:5432/mantle", "localhost"},
+		{"remote", "postgres://user:pass@db.example.com:5432/mydb", "db.example.com"},
+		{"ipv4", "postgres://user:pass@10.0.0.1:5432/mydb", "10.0.0.1"},
+		{"ipv6", "postgres://user:pass@[::1]:5432/mydb", "::1"},
+		{"no-port", "postgres://user:pass@myhost/mydb", "myhost"},
+		{"empty", "", ""},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, parseHostFromURL(tt.url))
+		})
+	}
+}