// Command myday is the MyDay entrypoint.
//
// It assembles config → core services → the registry → the door and serves
// (SPEC-003 §3). Any address may be bound (D-025 revised / D-043): the
// bootstrap is protected per request — in setup mode the door serves only the
// direct SSH tunnel — not by refusing a non-loopback bind.
//
// Spec: docs/specs/spec-003-core-door.md, docs/specs/spec-006-enroll-login.md.
package main

import (
	"context"
	"fmt"
	"log/slog"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/audit"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/auth"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/auth/flow"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/auth/totp"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/auth/webauthn"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/config"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/httpx"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/mail"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/module"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/recovery"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/server"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/setup"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/store"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/users"
	"git.lohmar.co.uk/cclohmar/NextMyDay/internal/core/web"

	// Build-time module discovery (D-028): blank-importing the aggregator runs
	// every module directory's init() self-registration. The generated file is
	// produced by `go generate ./internal/modules`.
	_ "git.lohmar.co.uk/cclohmar/NextMyDay/internal/modules"
)

// envConfigPath lets an operator point at a non-default config file
// (D-010: "env override"). It overrides the config path only.
const envConfigPath = "MYDAY_CONFIG"

func main() {
	if err := run(); err != nil {
		slog.Error("myday: fatal", "error", err)
		os.Exit(1)
	}
}

func run() error {
	cfgPath := config.FileName
	if p := os.Getenv(envConfigPath); p != "" {
		cfgPath = p
	}

	cfg, err := config.Load(cfgPath)
	if err != nil {
		return err
	}
	slog.Info("myday: config loaded", "source", cfg.Source(), "setup", cfg.Setup)

	// The core owns the DB connection and the migration runner (D-036 §12.1).
	db, err := store.Open(cfg.Database.Path)
	if err != nil {
		return err
	}
	defer func() { _ = db.Close() }()
	if err := db.Migrate(); err != nil {
		return err
	}

	// SPEC-008: build-time discovery (D-028) + the runtime registry. Modules
	// register themselves from init(); Load applies the `modules:` config map
	// (D-038). The core owns the migration runner (AC-5): module migrations run
	// in registration order, after the core schema, each version prefixed with
	// the module name.
	modules, err := module.Load(cfg.Modules)
	if err != nil {
		return err
	}
	if err := store.RunMigrations(db.DB, modules.Migrations()); err != nil {
		return fmt.Errorf("myday: module migrations: %w", err)
	}
	modules.LogLoaded(slog.Default()) // AC-2: a visible registry beats hidden magic

	// SPEC-009 §4: the shell's nav comes from the module registry (D-038) — a
	// disabled module's entry is absent. Set once, here: the same single,
	// explicit wiring point as discovery (D-028).
	web.SetNav(modules)

	aud := audit.New(db.DB)
	us := users.New(db.DB, aud)

	// The TOTP sealer (A9) needs an exactly-32-byte key.
	//
	// R-6 + D-041: the /setup wizard enrolls the admin's TOTP secret BEFORE it
	// persists the generated secrets (step 2b precedes `finish`), and that
	// secret is sealed with this key — so the key must exist when the process
	// STARTS. A first boot from config.example.yaml (placeholder secrets)
	// otherwise failed with "auth: no TOTP sealer configured" on
	// `admin.totp.begin` and the documented bootstrap could never complete.
	// R-6 already rules that a placeholder is replaced with a strong generated
	// value, so generate it here; it is adopted (and thereby persisted by the
	// wizard's `finish`, which skips a non-placeholder) only in setup mode.
	sealerKey, generatedKey, err := prepareTOTPKey(cfg)
	if err != nil {
		return err
	}
	sealer, err := auth.NewAEADSealer([]byte(sealerKey))
	if err != nil {
		return fmt.Errorf("myday: build TOTP sealer: %w", err)
	}

	core := auth.New(db.DB, aud,
		auth.WithEnrollWindow(cfg.EnrollWindow()),
		auth.WithSealer(sealer))
	ids := core.Identities()
	sessions := core.Sessions()

	// Setup mode (SPEC-005 §3): `config.setup` OR the instance is not yet
	// bootstrapped (no user, or no ACTIVE admin). It is LATCHED at startup, so
	// the wizard can run to completion in this process — mid-wizard the admin
	// exists but is still pending, and a live "no user" check would end setup
	// mode too early. The wizard clears it via Done(); `config.Setup` is the
	// startup flag and is never mutated (so the door reads it race-free).
	bootstrapped := func() bool {
		ctx := context.Background()
		n, err := us.Count(ctx)
		if err != nil || n == 0 {
			return false // fail-safe: an unreadable count means "not bootstrapped"
		}
		idn, err := ids.ByUserID(ctx, 1)
		if err != nil {
			return false
		}
		return idn.Status == auth.StatusActive
	}
	inSetup := cfg.Setup || !bootstrapped()

	// Adopt a generated TOTP key only where it is legitimate: a first boot
	// (setup mode). Outside setup mode a placeholder is a configuration fault
	// and the process refuses to start (the fail-closed rule, SPEC-003 §1).
	if generatedKey {
		if !inSetup {
			return fmt.Errorf("myday: secrets.totp_encryption_key must be exactly %d bytes (SPEC-003 D-2)",
				auth.KeySize)
		}
		cfg.Secrets.TOTPEncryptionKey = sealerKey
		slog.Info("myday: generated secrets.totp_encryption_key for setup (R-6) — " +
			"the wizard enrolls TOTP before it persists, so the key must exist now")
	}

	// M1s: the CSRF and cookie signing keys drive the whole pre-session
	// ceremony (A15), so they must be strong from the FIRST request too — not
	// only after `finish` persists them (which would leave the wizard signing
	// with the shipped, publicly-known placeholder until a restart). Generated
	// here in setup mode only; `finish` then persists these very values.
	if inSetup {
		generated, err := prepareSigningKeys(cfg)
		if err != nil {
			return err
		}
		for _, name := range generated {
			slog.Info("myday: generated a strong signing key for setup (R-6/M1s)", "name", name)
		}
	}

	csrf, err := httpx.NewCSRF([]byte(cfg.Secrets.CSRFKey))
	if err != nil {
		return err
	}
	// A15: the anonymous enroll/login forms carry a signed double-submit cookie.
	// Its `Secure` flag is resolved per request by the door (D-043).
	preSession, err := httpx.NewPreSessionCSRF([]byte(cfg.Secrets.CookieSecret))
	if err != nil {
		return err
	}

	var setupFlow *setup.Actions
	setupMode := func() bool {
		if setupFlow != nil && setupFlow.Done() {
			return false
		}
		return inSetup
	}

	// SPEC-006: the enroll/login flow (WebAuthn + TOTP). The passkey nudge
	// (SPEC-006 §8) is suppressed in setup mode — a loopback passkey is
	// unusable at the public domain (D-041).
	wa, err := webauthn.New(webauthnConfig(cfg.Server.BaseURL))
	if err != nil {
		return fmt.Errorf("myday: build webauthn: %w", err)
	}
	totpSvc := totp.New("MyDay", ids)
	authFlow, err := flow.New(flow.Deps{
		Identities:    ids,
		Credentials:   ids,
		Sessions:      sessions,
		Users:         us,
		WebAuthn:      wa,
		TOTP:          totpSvc,
		CSRF:          preSession,
		Audit:         aud,
		SuppressNudge: setupMode,
		BaseURL:       cfg.Server.BaseURL,
		Logger:        slog.Default(),
	})
	if err != nil {
		return err
	}

	// SPEC-005 §4 + D-041: the wizard enrolls the top admin with TOTP ONLY —
	// no passkey, because it would bind RP ID 127.0.0.1 over loopback. It reuses
	// the SPEC-006 TOTP ceremony through a TOTP-only flow (TOTPOnlyEnroll) whose
	// successful ceremony lands back on the wizard.
	wizardFlow, err := flow.New(flow.Deps{
		Identities:     ids,
		Credentials:    ids,
		Sessions:       sessions,
		Users:          us,
		WebAuthn:       wa,
		TOTP:           totpSvc,
		CSRF:           preSession,
		Audit:          aud,
		TOTPOnlyEnroll: true,
		SuccessPath:    func(string) string { return "/setup" },
		BaseURL:        cfg.Server.BaseURL,
		Logger:         slog.Default(),
	})
	if err != nil {
		return err
	}

	setupFlow, err = setup.New(setup.Deps{
		Config:     cfg,
		ConfigPath: configTarget(cfg),
		Users:      us,
		Identities: ids,
		Enroll:     wizardFlow,
		Audit:      aud,
		CSRF:       preSession,
		Logger:     slog.Default(),
	})
	if err != nil {
		return err
	}

	// SPEC-007: the recovery flow (manager escalation) and the config-gated
	// admin recovery. Mail is best-effort: with no SMTP host the fallback Nop
	// mailer discards delivery (and logs it).
	var mailer mail.Mailer = mail.Nop{}
	if cfg.Mail.Host != "" {
		mailer = mail.NewSMTP(cfg.Mail.Host, cfg.Mail.Port, cfg.Mail.Username, cfg.Mail.Password, cfg.Mail.From)
	} else if !inSetup {
		slog.Warn("myday: mail.host is not configured — recovery notifications will not be delivered")
	}

	recoveryRequests := recovery.NewStore(db.DB, aud)
	recoveryFlow, err := recovery.New(recovery.Deps{
		Requests:   recoveryRequests,
		Users:      us,
		Identities: ids,
		Mailer:     mailer,
		CSRF:       preSession,
		Audit:      aud,
		BaseURL:    cfg.Server.BaseURL,
		PendingTTL: recovery.DefaultPendingTTL,
		Logger:     slog.Default(),
	})
	if err != nil {
		return err
	}

	// SPEC-007 §5 (D-033): admin recovery runs at startup ONLY when the config
	// approval flag is set. It rotates user 1's identity, emails the enrolment
	// link to the address on record, audits, and clears the flag. Without the
	// flag nothing happens (dual control, AC-5). It never runs mid-bootstrap.
	if !setupMode() {
		acted, err := recovery.RunAdminRecovery(context.Background(), recovery.AdminDeps{
			Config:     cfg,
			ConfigPath: configTarget(cfg),
			Users:      us,
			Identities: ids,
			Mailer:     mailer,
			Audit:      aud,
			BaseURL:    cfg.Server.BaseURL,
			Logger:     slog.Default(),
		})
		if err != nil {
			return err
		}
		if acted {
			slog.Warn("myday: admin recovery rotated user 1's identity — " +
				"the enrolment link was emailed to the address on record")
		}
	}

	// SPEC-008 §7: the core Modules page (D-038). It is a CORE page carried by
	// the `core` dispatch module; the role gate below restricts it to the admin.
	console, err := module.NewPage(module.PageDeps{
		Registry:   modules,
		Config:     cfg,
		ConfigPath: configTarget(cfg),
		Audit:      aud,
		Logger:     slog.Default(),
	})
	if err != nil {
		return err
	}

	reg := buildRegistry(authFlow, setupFlow, recoveryFlow, modules, console)

	srv, err := server.New(server.Deps{
		Config:     cfg,
		Resolver:   ids,
		Registry:   reg,
		Sessions:   sessions,
		Identities: ids,
		Users:      us,
		Audit:      aud,
		CSRF:       csrf,
		PreSession: preSession,
		SetupMode:  setupMode,
		// SPEC-007: the tiered role gate (D-034). The floor admits any
		// authenticated user; role-ABOVE rules live in the services.
		// SPEC-008: the Modules page is admin-only — toggling modules changes
		// what the whole instance can do.
		RoleGate: server.NewTiers().
			Require(module.ConsoleModule, module.FunctionModules, users.RoleAdmin).
			Require(module.ConsoleModule, module.FunctionToggle, users.RoleAdmin),
	})
	if err != nil {
		return err
	}

	// SPEC-008 §4: run each enabled module's optional background work.
	if err := modules.Start(context.Background()); err != nil {
		return err
	}

	if setupMode() {
		slog.Warn("myday: SETUP MODE — serving /setup over the direct SSH tunnel only; " +
			"bootstrap via `ssh -L 8080:127.0.0.1:8080` before exposing this instance")
	}

	if err := srv.Serve(cfg.Server.Listen); err != nil {
		return err
	}
	return nil
}

// buildRegistry assembles the door's dispatch registry (SPEC-008 owns the
// discovered set; this is the surface the door dispatches against).
func buildRegistry(authFlow *flow.Actions, setupFlow *setup.Actions, recoveryFlow *recovery.Actions, mods *module.Registry, console *module.Page) *server.MapRegistry {
	reg := server.NewMapRegistry()

	// Core level-1 workflows (reserved: home · access · setup · static).
	reg.RegisterCore("home", server.Home)

	// SPEC-009 §3: the reserved `static` workflow serves the embedded web
	// assets. It is core owned and is served in setup mode too, so the
	// bootstrap wizard has a stylesheet (SPEC-005 §3).
	reg.RegisterCore(server.StaticWorkflow, server.StaticHandler())

	// SPEC-005: the /setup wizard (the page + its steps).
	if setupFlow != nil {
		server.RegisterSetupFlow(reg, setupFlow)
	}

	// SPEC-008: the discovered modules (D-028) — the `home` dashboard among
	// them. A disabled module is not mounted, so its routes 404 (D-038).
	if mods != nil {
		mods.Mount(reg)
	}

	// SPEC-006: the enroll/login screens + the `auth` action module.
	if authFlow != nil {
		server.RegisterAuthFlow(reg, authFlow)
	}

	// SPEC-007: the /access recovery entry + the approve/deny actions. It
	// extends the `auth` module registered above (or creates it).
	if recoveryFlow != nil {
		server.RegisterRecoveryFlow(reg, recoveryFlow)
	} else {
		reg.RegisterCore("access", server.AccessPlaceholder)
	}

	// SPEC-008 §7: the core Modules page (GET /{GUID}/core/modules · POST
	// /{GUID}?do=core&action=modules.toggle).
	if console != nil {
		console.Register(reg)
	}

	return reg
}

// prepareTOTPKey returns the TOTP sealing key the process will use, generating
// a strong one when the configured value is a placeholder (R-6/D-1). generated
// reports that the value was minted here — run() adopts it only in setup mode,
// where the process must still be able to seal a ceremony result.
//
// An operator-supplied key of the wrong size fails closed: rather than run a
// ceremony whose result we cannot store (A9), say so and stop.
func prepareTOTPKey(cfg *config.Config) (key string, generated bool, err error) {
	key = cfg.Secrets.TOTPEncryptionKey
	if config.SecretIsPlaceholder(key) {
		// 24 bytes -> 32 base64url chars == auth.KeySize.
		key, err = config.GenerateSecret(24)
		if err != nil {
			return "", false, err
		}
		return key, true, nil
	}
	if len(key) != auth.KeySize {
		return "", false, fmt.Errorf("myday: secrets.totp_encryption_key must be exactly %d bytes, got %d",
			auth.KeySize, len(key))
	}
	return key, false, nil
}

// prepareSigningKeys replaces placeholder CSRF / cookie signing keys with strong
// generated values (R-6/M1s) and returns the names of the secrets it generated.
//
// run() calls it only in setup mode: the wizard's pre-session double-submit
// ceremony (A15) is signed with these keys from the first request, so the
// shipped, publicly-known placeholder must never be used. In productive mode
// config.Validate already refuses a placeholder (fail closed, SPEC-003 §1).
func prepareSigningKeys(cfg *config.Config) (generated []string, err error) {
	for _, s := range []struct {
		name string
		dst  *string
	}{
		{"secrets.csrf_key", &cfg.Secrets.CSRFKey},
		{"secrets.cookie_secret", &cfg.Secrets.CookieSecret},
	} {
		if !config.SecretIsPlaceholder(*s.dst) {
			continue
		}
		v, err := config.GenerateSecret(32)
		if err != nil {
			return generated, err
		}
		*s.dst = v
		generated = append(generated, s.name)
	}
	return generated, nil
}

// configTarget picks where the wizard persists settings: `config.yaml` beside
// the loaded file. It NEVER overwrites the committed `config.example.yaml`
// (D-010) — so a dev run on the example writes a real config.yaml next to it.
func configTarget(cfg *config.Config) string {
	src := cfg.Source()
	if filepath.Base(src) == config.ExampleFileName {
		return filepath.Join(filepath.Dir(src), config.FileName)
	}
	return src
}

// webauthnConfig derives the Relying Party configuration from server.base_url.
// An empty/unparseable base URL falls back to loopback, which keeps setup mode
// (the tunnel-only gate, D-025) working before the domain is configured.
func webauthnConfig(baseURL string) webauthn.Config {
	defaultCfg := webauthn.Config{
		RPID:          "localhost",
		RPDisplayName: "MyDay",
		RPOrigins:     []string{"http://localhost"},
	}
	u, err := url.Parse(strings.TrimSpace(baseURL))
	if err != nil || u.Host == "" || u.Scheme == "" {
		return defaultCfg
	}
	return webauthn.Config{
		RPID:          u.Hostname(),
		RPDisplayName: "MyDay",
		RPOrigins:     []string{u.Scheme + "://" + u.Host},
	}
}