package web

import (
	"context"
	"errors"
	"net/http"
	"strconv"
	"strings"

	"gitea.mynodes.xyz/ilker/llmgw/internal/store"
)

// The cluster's settings, edited in the browser (BACKLOG E4): the document
// `llmgw ctl config edit` opens, for whoever has no terminal on a control
// plane. The same rules hold here as there — a version is checked as a
// control plane would load it before it is kept, it is made from the newest
// version or refused, and every change is in force on every control plane
// within seconds and in the audit log.

// SettingsAdmin is where the cluster's settings are kept.
type SettingsAdmin interface {
	ClusterSettings(ctx context.Context) (store.SettingsVersion, error)
	ClusterSettingsAt(ctx context.Context, version int64) (store.SettingsVersion, error)
	ClusterSettingsHistory(ctx context.Context, limit int) ([]store.SettingsVersion, error)
	PutClusterSettings(ctx context.Context, base int64, body, by, note string) (int64, error)
}

type settingsPageData struct {
	Nav     Nav
	Version string
	CSRF    string
	// Current is the version in force; Shown the one in the editor, which
	// is an earlier one when ?version= asked for it.
	Current, Shown store.SettingsVersion
	Earlier        bool
	// Body is what the editor holds: the version shown, or what was sent
	// and refused, so a refusal does not lose the edit.
	Body      string
	Note      string
	History   []settingsRow
	LocalKeys []string
	Notice    string
	Error     string
}

type settingsRow struct {
	Version  int64
	At, By   string
	Note     string
	InForce  bool
	Selected bool
}

// RegisterAdminSettings mounts /admin/settings, for administrators only:
// the settings hold webhook addresses and the like, so even reading them is
// not every staff role's.
func (p *AccountPages) RegisterAdminSettings(mux *http.ServeMux, s SettingsAdmin, check func([]byte) error, localKeys []string) {
	p.hasSettings = true
	page := func(w http.ResponseWriter, r *http.Request, admin store.User, d settingsPageData) {
		ctx, l := r.Context(), langOf(r)
		d.Nav, d.Version, d.CSRF, d.LocalKeys = p.navFor(r, admin, "settings"), p.version, csrfFor(r), localKeys
		cur, err := s.ClusterSettings(ctx)
		if err != nil {
			d.Error = l.Err(err)
		}
		d.Current = cur
		if d.Shown.Version == 0 {
			d.Shown = cur
		}
		d.Earlier = d.Shown.Version != cur.Version
		if d.Body == "" {
			d.Body = d.Shown.Body
		}
		if hist, err := s.ClusterSettingsHistory(ctx, 30); err == nil {
			for _, v := range hist {
				d.History = append(d.History, settingsRow{Version: v.Version, At: l.Date(v.At.UTC()) + " " + v.At.UTC().Format("15:04"),
					By: v.By, Note: v.Note, InForce: v.Version == cur.Version, Selected: v.Version == d.Shown.Version})
			}
		}
		noStore(w)
		render(w, r, "admin_settings", d)
	}
	adminsOnly := func(next func(w http.ResponseWriter, r *http.Request, admin store.User)) http.HandlerFunc {
		return p.adminOnly(func(w http.ResponseWriter, r *http.Request, admin store.User) {
			if !admin.IsAdmin {
				http.NotFound(w, r)
				return
			}
			if r.Method == http.MethodPost {
				sess, _, _ := p.session(r)
				if !p.accounts.CheckCSRF(sess, r.FormValue("csrf")) {
					http.Error(w, "bad request", http.StatusBadRequest)
					return
				}
			}
			next(w, r, admin)
		})
	}

	mux.HandleFunc("GET /admin/settings", adminsOnly(func(w http.ResponseWriter, r *http.Request, admin store.User) {
		var d settingsPageData
		if q := r.URL.Query().Get("version"); q != "" {
			n, err := strconv.ParseInt(q, 10, 64)
			if v, verr := s.ClusterSettingsAt(r.Context(), n); err == nil && verr == nil && v.Version != 0 {
				d.Shown = v
			} else {
				d.Error = langOf(r).T("settings.err.no_version")
			}
		}
		page(w, r, admin, d)
	}))

	mux.HandleFunc("POST /admin/settings", adminsOnly(func(w http.ResponseWriter, r *http.Request, admin store.User) {
		l := langOf(r)
		body := strings.ReplaceAll(r.FormValue("body"), "\r\n", "\n")
		note := strings.TrimSpace(r.FormValue("note"))
		base, _ := strconv.ParseInt(r.FormValue("base"), 10, 64)
		// The audit line records the form; the document can hold webhook
		// secrets, so it records the document's size, not the document.
		r.PostForm.Set("body", "("+strconv.Itoa(len(body))+" bytes)")
		refuse := func(msg string) {
			noteAudit(r, "cluster settings", "", msg)
			page(w, r, admin, settingsPageData{Body: body, Note: note, Error: msg})
		}
		if cur, err := s.ClusterSettings(r.Context()); err == nil && cur.Body == body {
			refuse(l.T("settings.err.unchanged"))
			return
		}
		if err := check([]byte(body)); err != nil {
			refuse(l.T("settings.err.invalid") + " " + err.Error())
			return
		}
		n, err := s.PutClusterSettings(r.Context(), base, body, admin.Email, note)
		switch {
		case errors.Is(err, store.ErrSettingsChanged):
			refuse(l.T("settings.err.changed"))
			return
		case err != nil:
			refuse(l.Err(err))
			return
		}
		noteAudit(r, "cluster settings", "version "+strconv.FormatInt(n, 10), "")
		page(w, r, admin, settingsPageData{Notice: l.T("settings.saved", n)})
	}))

	mux.HandleFunc("POST /admin/settings/rollback", adminsOnly(func(w http.ResponseWriter, r *http.Request, admin store.User) {
		l := langOf(r)
		n, _ := strconv.ParseInt(r.FormValue("version"), 10, 64)
		old, err := s.ClusterSettingsAt(r.Context(), n)
		if err != nil || old.Version == 0 {
			page(w, r, admin, settingsPageData{Error: l.T("settings.err.no_version")})
			return
		}
		cur, err := s.ClusterSettings(r.Context())
		if err != nil {
			page(w, r, admin, settingsPageData{Error: l.Err(err)})
			return
		}
		if err := check([]byte(old.Body)); err != nil {
			// A version kept before a change to server.yaml may no longer
			// load beside it; refused here rather than breaking the cluster.
			noteAudit(r, "cluster settings", "", err.Error())
			page(w, r, admin, settingsPageData{Error: l.T("settings.err.invalid") + " " + err.Error()})
			return
		}
		v, err := s.PutClusterSettings(r.Context(), cur.Version, old.Body, admin.Email, "back to version "+strconv.FormatInt(n, 10))
		if err != nil {
			page(w, r, admin, settingsPageData{Error: l.Err(err)})
			return
		}
		noteAudit(r, "cluster settings", "version "+strconv.FormatInt(v, 10)+" from "+strconv.FormatInt(n, 10), "")
		page(w, r, admin, settingsPageData{Notice: l.T("settings.rolled_back", n, v)})
	}))
}