package jmap

import (
	"encoding/json"
	"net/http"
	"strconv"
)

// sessionCapability is one entry under the Session object's "capabilities" (account-
// independent) or an account's own "accountCapabilities" — both are just
// urn -> settings-object maps, an empty object being valid when a capability has no
// extra settings to advertise (RFC 8620 §2).
type sessionCapability = map[string]any

type sessionAccount struct {
	Name                string                       `json:"name"`
	IsPersonal          bool                         `json:"isPersonal"`
	IsReadOnly          bool                         `json:"isReadOnly"`
	AccountCapabilities map[string]sessionCapability `json:"accountCapabilities"`
}

type sessionResponse struct {
	Capabilities    map[string]sessionCapability `json:"capabilities"`
	Accounts        map[string]sessionAccount    `json:"accounts"`
	PrimaryAccounts map[string]string            `json:"primaryAccounts"`
	Username        string                       `json:"username"`
	APIURL          string                       `json:"apiUrl"`
	DownloadURL     string                       `json:"downloadUrl"`
	UploadURL       string                       `json:"uploadUrl"`
	EventSourceURL  string                       `json:"eventSourceUrl"`
	State           string                       `json:"state"`
}

const (
	capCore       = "urn:ietf:params:jmap:core"
	capMail       = "urn:ietf:params:jmap:mail"
	capSubmission = "urn:ietf:params:jmap:submission"
)

// handleSession serves the RFC 8620 §2 Session resource — the entry point a JMAP
// client fetches once (and re-fetches on the Basic realm challenge/whenever the
// server's "state" changes) to discover every other endpoint URL and this account's
// capabilities.
func (b *Backend) handleSession(w http.ResponseWriter, r *http.Request) {
	mbox := mailboxFromContext(r)
	accountID := strconv.FormatInt(mbox.ID, 10)

	maxSize := b.Cfg.Section("Mailstore").Key("max_message_bytes").MustInt64(25 * 1024 * 1024)

	resp := sessionResponse{
		Capabilities: map[string]sessionCapability{
			capCore: {
				"maxSizeUpload":         maxSize,
				"maxConcurrentUpload":   4,
				"maxSizeRequest":        maxSize,
				"maxConcurrentRequests": 4,
				"maxCallsInRequest":     32,
				"maxObjectsInGet":       500,
				"maxObjectsInSet":       500,
				"collationAlgorithms":   []string{},
			},
			capMail:       {},
			capSubmission: {},
		},
		Accounts: map[string]sessionAccount{
			accountID: {
				Name:       mbox.Email,
				IsPersonal: true,
				IsReadOnly: false,
				AccountCapabilities: map[string]sessionCapability{
					capCore: {}, capMail: {}, capSubmission: {},
				},
			},
		},
		PrimaryAccounts: map[string]string{
			capMail:       accountID,
			capSubmission: accountID,
		},
		Username:       mbox.Email,
		APIURL:         "/jmap/api",
		DownloadURL:    "/jmap/download/{accountId}/{blobId}/{name}?type={type}",
		UploadURL:      "/jmap/upload/{accountId}",
		EventSourceURL: "/jmap/eventsource?types={types}&closeafter={closeafter}&ping={ping}",
	}
	state, err := b.DB.MessagesState(mbox.ID)
	if err != nil {
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	resp.State = state

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp)
}