package web

import (
	"net/http"
	"strings"
)

// Phase 5j Slice C — system views. Per m's Q1 pick (b) (2026-05-29):
// FULL MIGRATION of the legacy pages into the /views/{slug} family.
// /, /dashboard, /calendar, /timeline, /graph all 301-redirect to their
// /views/{system-slug} counterparts; the handlers stay (now reachable
// under the new URL).
//
// System views are code-resident — they never appear as rows in
// projax.views. Their slugs are reserved at the validator level (see
// store.IsReservedViewSlug) so user-created views can't shadow them.

// SystemView is a code-resident view definition. The sidebar's Views
// section (slice E) lists every entry returned by AllSystemViews
// alongside user views. The render path for system slugs goes directly
// to the legacy handler (handleTree / handleDashboard / …); the struct
// here is metadata for navigation, not a render spec.
type SystemView struct {
	Slug string
	Name string
	Icon string
	URL  string // /views/{slug}
}

// AllSystemViews returns every code-resident view in display order. Used
// by the sidebar (slice E) and the reserved-slug validation (slice A
// already pre-seeded the same slugs in store.IsReservedViewSlug — keep
// in sync with this list).
func AllSystemViews() []SystemView {
	return []SystemView{
		{Slug: "tree", Name: "Tree", Icon: "tree", URL: "/views/tree"},
		{Slug: "dashboard", Name: "Dashboard", Icon: "dashboard", URL: "/views/dashboard"},
		{Slug: "calendar", Name: "Calendar", Icon: "calendar", URL: "/views/calendar"},
		{Slug: "timeline", Name: "Timeline", Icon: "clock", URL: "/views/timeline"},
		{Slug: "graph", Name: "Graph", Icon: "graph", URL: "/views/graph"},
	}
}

// LookupSystemView returns the SystemView matching slug, or nil. Used by
// handleViewRender's fallback path and by tests that need to assert
// metadata.
func LookupSystemView(slug string) *SystemView {
	for _, sv := range AllSystemViews() {
		if sv.Slug == slug {
			s := sv
			return &s
		}
	}
	return nil
}

// legacyRedirect returns a handler that 301s the legacy URL onto its
// /views/{system-slug} counterpart. Per m's Q3 pick (b): when the
// request carries a legacy `?view=<uuid>` param (the 5i overlay scheme)
// the redirect resolves the uuid → current slug so old bookmarks land
// on the user view they pointed at. A miss falls through to the system
// slug.
func (s *Server) legacyRedirect(systemSlug string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// /  is a path-prefix in Go's mux; only redirect when the request
		// path is exactly "/". Any other root-relative path that fell
		// through to GET / (e.g. "/some-unknown") gets a 404.
		if systemSlug == "tree" && r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		target := "/views/" + systemSlug
		if id := strings.TrimSpace(r.URL.Query().Get("view")); id != "" {
			if v, err := s.Store.GetViewByID(r.Context(), id); err == nil && v != nil {
				target = "/views/" + v.Slug
			}
		}
		// Preserve any non-`view` query params so existing bookmarks
		// carrying ?tag=… etc. still narrow the redirected view.
		q := r.URL.Query()
		q.Del("view")
		if encoded := q.Encode(); encoded != "" {
			target += "?" + encoded
		}
		http.Redirect(w, r, target, http.StatusMovedPermanently)
	}
}