package httpapi

import (
	"context"
	"errors"
	"net/http"
	"time"

	"github.com/urpi/go-bananas/internal/auth"
	"github.com/urpi/go-bananas/internal/config"
	"github.com/urpi/go-bananas/internal/domain"
	"github.com/urpi/go-bananas/internal/store"
	"github.com/urpi/go-bananas/internal/tokenengine"
)

// AuthHandlers serves the browser-facing authentication routes and the session
// introspection the admin UI needs.
type AuthHandlers struct {
	authenticator *auth.Authenticator
	// store is used only to read the caller's own interface preferences, which
	// are reported alongside the session so the UI can preselect a theme from the
	// same round trip that establishes who the caller is. It is nil in tests that
	// do not exercise preferences.
	store  *store.Store
	log    Logger
	config config.Config
}

// NewAuthHandlers builds the auth handler set.
func NewAuthHandlers(authenticator *auth.Authenticator, st *store.Store, log Logger, cfg config.Config) *AuthHandlers {
	return &AuthHandlers{authenticator: authenticator, store: st, log: log, config: cfg}
}

// Login starts the OIDC login flow.
func (h *AuthHandlers) Login(w http.ResponseWriter, r *http.Request) {
	// Sanitised here as well as in the state store, so that the value that is
	// reflected back to the provider-side cookie is already known to be local.
	returnTo := auth.SafeReturnTo(r.URL.Query().Get("returnTo"))

	if h.authenticator == nil || !h.authenticator.ModeConfigured() {
		writeError(w, r, http.StatusNotFound, CodeNotConfigured,
			"this deployment does not use interactive login", nil)
		return
	}

	if err := h.authenticator.Begin(r.Context(), r, w, returnTo); err != nil {
		h.log.Error("begin login", "error", err)
		writeError(w, r, http.StatusBadGateway, CodeInternal,
			"could not start the login flow with the identity provider", nil)
	}
}

// Callback completes the OIDC login flow.
func (h *AuthHandlers) Callback(w http.ResponseWriter, r *http.Request) {
	if h.authenticator == nil || !h.authenticator.ModeConfigured() {
		writeError(w, r, http.StatusNotFound, CodeNotConfigured,
			"this deployment does not use interactive login", nil)
		return
	}

	login, err := h.authenticator.Complete(r.Context(), r)
	if err != nil {
		// A failed login is a normal occurrence, not a server fault: the user may
		// have declined consent or the state cookie may have expired. Log it and
		// show a clear message rather than a stack trace.
		if errors.Is(err, domain.ErrUnauthorized) {
			h.log.Info("login rejected", "reason", err.Error(), "ip", clientIPFrom(r.Context()))
			writeError(w, r, http.StatusUnauthorized, CodeUnauthorized,
				"the login could not be completed: "+cleanError(err), nil)
			return
		}
		h.log.Error("complete login", "error", err)
		writeError(w, r, http.StatusBadGateway, CodeInternal,
			"the identity provider returned an unexpected response", nil)
		return
	}

	// The login transaction is single-use; discard it so a replayed callback
	// cannot reuse the PKCE verifier.
	h.authenticator.ClearState(w)

	if err := h.authenticator.IssueSession(r.Context(), w, login.Identity); err != nil {
		h.log.Error("issue session", "error", err)
		writeError(w, r, http.StatusInternalServerError, CodeInternal,
			"could not establish a session", nil)
		return
	}

	h.log.Info("login succeeded",
		"subject", login.Identity.Subject,
		"email", login.Identity.Email,
		"roles", login.Identity.Roles,
		"ip", clientIPFrom(r.Context()),
	)

	// The destination comes from the transaction cookie, which was sanitised when
	// the login began and signed, so it cannot have been influenced by whatever
	// the provider chose to append to the callback URL.
	//nolint:gosec // G710: the value is not the raw request parameter. It is the
	// sanitised destination the signed transaction cookie carried, and SafeReturnTo
	// is the only way to produce one: it rejects absolute URLs, protocol-relative
	// URLs, backslashes and control characters, and falls back to "/" otherwise.
	http.Redirect(w, r, auth.SafeReturnTo(login.ReturnTo), http.StatusFound)
}

// Logout ends the session and, when an OIDC provider is configured, the provider
// session too.
func (h *AuthHandlers) Logout(w http.ResponseWriter, r *http.Request) {
	if h.authenticator != nil {
		identity := mustIdentity(r.Context())
		h.authenticator.ClearSession(w)
		if identity.Method != "anonymous" {
			h.log.Info("logout", "subject", identity.Subject, "ip", clientIPFrom(r.Context()))
		}
	}

	if h.authenticator == nil || !h.authenticator.ProviderEnabled() {
		http.Redirect(w, r, "/", http.StatusFound)
		return
	}

	target := h.authenticator.LogoutURL(h.config.PostLogoutRedirectURL())
	if target == "" {
		http.Redirect(w, r, "/", http.StatusFound)
		return
	}
	http.Redirect(w, r, target, http.StatusFound)
}

// Me returns the current session, if any.
//
// It always answers 200 with an explicit authenticated flag rather than 401 when
// there is no session, because "not logged in yet" is the normal state on first
// load and is not an error the UI should have to handle as one.
func (h *AuthHandlers) Me(w http.ResponseWriter, r *http.Request) {
	identity, err := identityFrom(r.Context())
	authenticated := err == nil && identity != nil && identity.Method != "anonymous"

	payload := map[string]any{
		"authenticated": authenticated,
		"mode":          h.authenticator.Mode(),
	}
	if authenticated {
		payload["identity"] = identity
		payload["permissions"] = permissionsFor(identity)
		// Reported with the session because the UI needs it to decide what to
		// paint on the first frame. A failure is reported as no choice rather than
		// as an error: a theme is a preference, not something worth refusing a
		// login over.
		if h.store != nil {
			if prefs, err := h.store.Preferences(r.Context(), identity.Subject); err != nil {
				h.log.Warn("read preferences for session", "subject", identity.Subject, "error", err)
				payload["preferences"] = domain.UserPreferences{}
			} else {
				payload["preferences"] = prefs
			}
		}
	}
	if h.authenticator != nil && h.authenticator.DevBypassEnabled() {
		payload["devBypass"] = true
	}
	if h.authenticator != nil && h.authenticator.ProviderEnabled() {
		// Deliberately this service's /auth/login rather than the provider's
		// authorization endpoint. A direct link to the provider would skip the
		// transaction cookie and the PKCE verifier, so the callback could not be
		// validated and the login would fail.
		payload["loginUrl"] = h.config.Path("/auth/login") + "?returnTo=%2F"
	}

	writeJSON(w, r, http.StatusOK, payload)
}

// Config returns the client-visible configuration the UI needs before login.
func (h *AuthHandlers) Config(w http.ResponseWriter, r *http.Request) {
	payload := map[string]any{
		"mode":              h.authenticator.Mode(),
		"issuer":            h.config.OIDCIssuer,
		"runtimeBase":       h.config.CDNBasis(),
		"publicBase":        h.config.Origin(),
		"basePath":          h.config.BasePath,
		"runtimeApiVersion": tokenengine.RuntimeAPIVersion,
		"variablePrefix":    tokenengine.VariablePrefix,
		"defaultTheme":      "",
	}
	writeJSON(w, r, http.StatusOK, payload)
}

// permissionsFor describes what the identity may do, so the UI can hide controls
// the API would reject anyway. The server still enforces every check: this is a
// convenience, not a security boundary.
func permissionsFor(identity *domain.Identity) map[string]bool {
	role := identity.HighestRole()
	return map[string]bool{
		"read":           role.AtLeast(domain.RoleViewer),
		"write":          role.AtLeast(domain.RoleEditor),
		"publish":        role.AtLeast(domain.RoleEditor),
		"delete":         role.AtLeast(domain.RoleAdmin),
		"manageKeys":     role.AtLeast(domain.RoleAdmin),
		"manageUsers":    role.AtLeast(domain.RoleAdmin),
		"manageSettings": role.AtLeast(domain.RoleAdmin),
	}
}

// -------------------------------------------------------- health probes --

// HealthHandlers serves the liveness and readiness probes.
type HealthHandlers struct {
	store   *store.Store
	cache   *ThemeCache
	version string
	config  config.Config
	// started is used to report uptime.
	started time.Time
}

// NewHealthHandlers builds the probe handlers.
func NewHealthHandlers(st *store.Store, cache *ThemeCache, version string, cfg config.Config) *HealthHandlers {
	return &HealthHandlers{
		store:   st,
		cache:   cache,
		version: version,
		config:  cfg,
		started: time.Now(),
	}
}

// Live is the liveness probe. It answers as long as the process can serve HTTP at
// all, and deliberately does not touch the database: a liveness probe that failed
// on a slow database would have the orchestrator restart a process that is
// perfectly healthy.
func (h *HealthHandlers) Live(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, r, http.StatusOK, map[string]any{
		"status":  "ok",
		"version": h.version,
		"uptime":  time.Since(h.started).Round(time.Second).String(),
	})
}

// Ready is the readiness probe. It reports whether the service can actually serve
// traffic, which means the database must answer within a bounded time.
func (h *HealthHandlers) Ready(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
	defer cancel()

	checks := map[string]any{}
	ready := true

	if err := h.store.Ping(ctx); err != nil {
		ready = false
		checks["database"] = map[string]any{"status": "error", "error": cleanError(err)}
	} else {
		entry := map[string]any{"status": "ok"}
		if h.store.InMemory() {
			// An in-memory database is legitimate in a test or a throwaway
			// container but never in production, so it is surfaced loudly rather
			// than silently accepted.
			entry["warning"] = "database is in-memory; all data is lost on restart"
		}
		checks["database"] = entry
	}

	if stats, err := h.store.Stats(ctx); err == nil {
		checks["themes"] = map[string]any{
			"status":        "ok",
			"count":         stats.Themes,
			"databaseBytes": stats.DatabaseSize,
		}
	}

	if h.cache != nil {
		checks["cache"] = map[string]any{"status": "ok", "entries": h.cache.Stats().Entries}
	}

	status := http.StatusOK
	state := "ready"
	if !ready {
		status = http.StatusServiceUnavailable
		state = "not ready"
	}

	writeJSON(w, r, status, map[string]any{"status": state, "checks": checks})
}