package main

import (
	"bytes"
	"database/sql"
	"fmt"
	"html/template"
	"image"
	"image/png"
	"io"
	"net/http"
	"strconv"
	"strings"

	"github.com/knadh/listmonk/internal/messenger"
	"github.com/knadh/listmonk/internal/subimporter"
	"github.com/knadh/listmonk/models"
	"github.com/labstack/echo"
	"github.com/lib/pq"
)

const (
	tplMessage = "message"
)

// tplRenderer wraps a template.tplRenderer for echo.
type tplRenderer struct {
	templates  *template.Template
	RootURL    string
	LogoURL    string
	FaviconURL string
}

// tplData is the data container that is injected
// into public templates for accessing data.
type tplData struct {
	RootURL    string
	LogoURL    string
	FaviconURL string
	Data       interface{}
}

type publicTpl struct {
	Title       string
	Description string
}

type unsubTpl struct {
	publicTpl
	SubUUID        string
	AllowBlocklist bool
	AllowExport    bool
	AllowWipe      bool
}

type optinTpl struct {
	publicTpl
	SubUUID   string
	ListUUIDs []string      `query:"l" form:"l"`
	Lists     []models.List `query:"-" form:"-"`
}

type msgTpl struct {
	publicTpl
	MessageTitle string
	Message      string
}

type subForm struct {
	subimporter.SubReq
	SubListUUIDs []string `form:"l"`
}

var (
	pixelPNG = drawTransparentImage(3, 14)
)

// Render executes and renders a template for echo.
func (t *tplRenderer) Render(w io.Writer, name string, data interface{}, c echo.Context) error {
	return t.templates.ExecuteTemplate(w, name, tplData{
		RootURL:    t.RootURL,
		LogoURL:    t.LogoURL,
		FaviconURL: t.FaviconURL,
		Data:       data,
	})
}

// handleViewCampaignMessage renders the HTML view of a campaign message.
// This is the view the {{ MessageURL }} template tag links to in e-mail campaigns.
func handleViewCampaignMessage(c echo.Context) error {
	var (
		app      = c.Get("app").(*App)
		campUUID = c.Param("campUUID")
		subUUID  = c.Param("subUUID")
	)

	// Get the campaign.
	var camp models.Campaign
	if err := app.queries.GetCampaign.Get(&camp, 0, campUUID); err != nil {
		if err == sql.ErrNoRows {
			return c.Render(http.StatusNotFound, tplMessage,
				makeMsgTpl("Not found", "", `The e-mail campaign was not found.`))
		}

		app.log.Printf("error fetching campaign: %v", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", `Error fetching e-mail campaign.`))
	}

	// Get the subscriber.
	var sub models.Subscriber
	if err := app.queries.GetSubscriber.Get(&sub, 0, subUUID); err != nil {
		if err == sql.ErrNoRows {
			return c.Render(http.StatusNotFound, tplMessage,
				makeMsgTpl("Not found", "", `The e-mail message was not found.`))
		}

		app.log.Printf("error fetching campaign subscriber: %v", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", `Error fetching e-mail message.`))
	}

	// Compile the template.
	if err := camp.CompileTemplate(app.manager.TemplateFuncs(&camp)); err != nil {
		app.log.Printf("error compiling template: %v", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", `Error compiling e-mail template.`))
	}

	// Render the message body.
	m := app.manager.NewCampaignMessage(&camp, sub)
	if err := m.Render(); err != nil {
		app.log.Printf("error rendering message: %v", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", `Error rendering e-mail message.`))
	}

	return c.HTML(http.StatusOK, string(m.Body()))
}

// handleSubscriptionPage renders the subscription management page and
// handles unsubscriptions. This is the view that {{ UnsubscribeURL }} in
// campaigns link to.
func handleSubscriptionPage(c echo.Context) error {
	var (
		app          = c.Get("app").(*App)
		campUUID     = c.Param("campUUID")
		subUUID      = c.Param("subUUID")
		unsub        = c.Request().Method == http.MethodPost
		blocklist, _ = strconv.ParseBool(c.FormValue("blocklist"))
		out          = unsubTpl{}
	)
	out.SubUUID = subUUID
	out.Title = "Unsubscribe from mailing list"
	out.AllowBlocklist = app.constants.Privacy.AllowBlocklist
	out.AllowExport = app.constants.Privacy.AllowExport
	out.AllowWipe = app.constants.Privacy.AllowWipe

	// Unsubscribe.
	if unsub {
		// Is blocklisting allowed?
		if !app.constants.Privacy.AllowBlocklist {
			blocklist = false
		}

		if _, err := app.queries.Unsubscribe.Exec(campUUID, subUUID, blocklist); err != nil {
			app.log.Printf("error unsubscribing: %v", err)
			return c.Render(http.StatusInternalServerError, tplMessage,
				makeMsgTpl("Error", "",
					`Error processing request. Please retry.`))
		}

		return c.Render(http.StatusOK, tplMessage,
			makeMsgTpl("Unsubscribed", "",
				`You have been successfully unsubscribed.`))
	}

	return c.Render(http.StatusOK, "subscription", out)
}

// handleOptinPage renders the double opt-in confirmation page that subscribers
// see when they click on the "Confirm subscription" button in double-optin
// notifications.
func handleOptinPage(c echo.Context) error {
	var (
		app        = c.Get("app").(*App)
		subUUID    = c.Param("subUUID")
		confirm, _ = strconv.ParseBool(c.FormValue("confirm"))
		out        = optinTpl{}
	)
	out.SubUUID = subUUID
	out.Title = "Confirm subscriptions"
	out.SubUUID = subUUID

	// Get and validate fields.
	if err := c.Bind(&out); err != nil {
		return err
	}

	// Validate list UUIDs if there are incoming UUIDs in the request.
	if len(out.ListUUIDs) > 0 {
		for _, l := range out.ListUUIDs {
			if !reUUID.MatchString(l) {
				return c.Render(http.StatusBadRequest, tplMessage,
					makeMsgTpl("Invalid request", "",
						`One or more UUIDs in the request are invalid.`))
			}
		}
	}

	// Get the list of subscription lists where the subscriber hasn't confirmed.
	if err := app.queries.GetSubscriberLists.Select(&out.Lists, 0, subUUID,
		nil, pq.StringArray(out.ListUUIDs), models.SubscriptionStatusUnconfirmed, nil); err != nil {
		app.log.Printf("error fetching lists for opt-in: %s", pqErrMsg(err))
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", `Error fetching lists. Please retry.`))
	}

	// There are no lists to confirm.
	if len(out.Lists) == 0 {
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("No subscriptions", "",
				`There are no subscriptions to confirm.`))
	}

	// Confirm.
	if confirm {
		if _, err := app.queries.ConfirmSubscriptionOptin.Exec(subUUID, pq.StringArray(out.ListUUIDs)); err != nil {
			app.log.Printf("error unsubscribing: %v", err)
			return c.Render(http.StatusInternalServerError, tplMessage,
				makeMsgTpl("Error", "",
					`Error processing request. Please retry.`))
		}
		return c.Render(http.StatusOK, tplMessage,
			makeMsgTpl("Confirmed", "",
				`Your subscriptions have been confirmed.`))
	}

	return c.Render(http.StatusOK, "optin", out)
}

// handleSubscriptionForm handles subscription requests coming from public
// HTML subscription forms.
func handleSubscriptionForm(c echo.Context) error {
	var (
		app = c.Get("app").(*App)
		req subForm
	)

	// Get and validate fields.
	if err := c.Bind(&req); err != nil {
		return err
	}

	if len(req.SubListUUIDs) == 0 {
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "",
				`No lists to subscribe to.`))
	}

	// If there's no name, use the name bit from the e-mail.
	req.Email = strings.ToLower(req.Email)
	if req.Name == "" {
		req.Name = strings.Split(req.Email, "@")[0]
	}

	// Validate fields.
	if err := subimporter.ValidateFields(req.SubReq); err != nil {
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", err.Error()))
	}

	// Insert the subscriber into the DB.
	req.Status = models.SubscriberStatusEnabled
	req.ListUUIDs = pq.StringArray(req.SubListUUIDs)
	if _, err := insertSubscriber(req.SubReq, app); err != nil {
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error", "", fmt.Sprintf("%s", err.(*echo.HTTPError).Message)))
	}

	return c.Render(http.StatusOK, tplMessage,
		makeMsgTpl("Done", "", `Subscribed successfully.`))
}

// handleLinkRedirect redirects a link UUID to its original underlying link
// after recording the link click for a particular subscriber in the particular
// campaign. These links are generated by {{ TrackLink }} tags in campaigns.
func handleLinkRedirect(c echo.Context) error {
	var (
		app      = c.Get("app").(*App)
		linkUUID = c.Param("linkUUID")
		campUUID = c.Param("campUUID")
		subUUID  = c.Param("subUUID")
	)

	// If individual tracking is disabled, do not record the subscriber ID.
	if !app.constants.Privacy.IndividualTracking {
		subUUID = ""
	}

	var url string
	if err := app.queries.RegisterLinkClick.Get(&url, linkUUID, campUUID, subUUID); err != nil {
		if pqErr, ok := err.(*pq.Error); ok && pqErr.Column == "link_id" {
			return c.Render(http.StatusNotFound, tplMessage,
				makeMsgTpl("Invalid link", "", "The requested link is invalid."))
		}

		app.log.Printf("error fetching redirect link: %s", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error opening link", "", "There was an error opening the link. Please try later."))
	}

	return c.Redirect(http.StatusTemporaryRedirect, url)
}

// handleRegisterCampaignView registers a campaign view which comes in
// the form of an pixel image request. Regardless of errors, this handler
// should always render the pixel image bytes. The pixel URL is is generated by
// the {{ TrackView }} template tag in campaigns.
func handleRegisterCampaignView(c echo.Context) error {
	var (
		app      = c.Get("app").(*App)
		campUUID = c.Param("campUUID")
		subUUID  = c.Param("subUUID")
	)

	// If individual tracking is disabled, do not record the subscriber ID.
	if !app.constants.Privacy.IndividualTracking {
		subUUID = ""
	}

	// Exclude dummy hits from template previews.
	if campUUID != dummyUUID && subUUID != dummyUUID {
		if _, err := app.queries.RegisterCampaignView.Exec(campUUID, subUUID); err != nil {
			app.log.Printf("error registering campaign view: %s", err)
		}
	}

	c.Response().Header().Set("Cache-Control", "no-cache")
	return c.Blob(http.StatusOK, "image/png", pixelPNG)
}

// handleSelfExportSubscriberData pulls the subscriber's profile, list subscriptions,
// campaign views and clicks and produces a JSON report that is then e-mailed
// to the subscriber. This is a privacy feature and the data that's exported
// is dependent on the configuration.
func handleSelfExportSubscriberData(c echo.Context) error {
	var (
		app     = c.Get("app").(*App)
		subUUID = c.Param("subUUID")
	)
	// Is export allowed?
	if !app.constants.Privacy.AllowExport {
		return c.Render(http.StatusBadRequest, tplMessage,
			makeMsgTpl("Invalid request", "", "The feature is not available."))
	}

	// Get the subscriber's data. A single query that gets the profile,
	// list subscriptions, campaign views, and link clicks. Names of
	// private lists are replaced with "Private list".
	data, b, err := exportSubscriberData(0, subUUID, app.constants.Privacy.Exportable, app)
	if err != nil {
		app.log.Printf("error exporting subscriber data: %s", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error processing request", "",
				"There was an error processing your request. Please try later."))
	}

	// Prepare the attachment e-mail.
	var msg bytes.Buffer
	if err := app.notifTpls.ExecuteTemplate(&msg, notifSubscriberData, data); err != nil {
		app.log.Printf("error compiling notification template '%s': %v",
			notifSubscriberData, err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error preparing data", "",
				"There was an error preparing your data. Please try later."))
	}

	// Send the data as a JSON attachment to the subscriber.
	const fname = "data.json"
	if err := app.messengers[emailMsgr].Push(messenger.Message{
		From:    app.constants.FromEmail,
		To:      []string{data.Email},
		Subject: "Your data",
		Body:    msg.Bytes(),
		Attachments: []messenger.Attachment{
			{
				Name:    fname,
				Content: b,
				Header:  messenger.MakeAttachmentHeader(fname, "base64"),
			},
		},
	}); err != nil {
		app.log.Printf("error e-mailing subscriber profile: %s", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error e-mailing data", "",
				"There was an error e-mailing your data. Please try later."))
	}
	return c.Render(http.StatusOK, tplMessage,
		makeMsgTpl("Data e-mailed", "",
			`Your data has been e-mailed to you as an attachment.`))
}

// handleWipeSubscriberData allows a subscriber to delete their data. The
// profile and subscriptions are deleted, while the campaign_views and link
// clicks remain as orphan data unconnected to any subscriber.
func handleWipeSubscriberData(c echo.Context) error {
	var (
		app     = c.Get("app").(*App)
		subUUID = c.Param("subUUID")
	)

	// Is wiping allowed?
	if !app.constants.Privacy.AllowWipe {
		return c.Render(http.StatusBadRequest, tplMessage,
			makeMsgTpl("Invalid request", "",
				"The feature is not available."))
	}

	if _, err := app.queries.DeleteSubscribers.Exec(nil, pq.StringArray{subUUID}); err != nil {
		app.log.Printf("error wiping subscriber data: %s", err)
		return c.Render(http.StatusInternalServerError, tplMessage,
			makeMsgTpl("Error processing request", "",
				"There was an error processing your request. Please try later."))
	}

	return c.Render(http.StatusOK, tplMessage,
		makeMsgTpl("Data removed", "",
			`Your subscriptions and all associated data has been removed.`))
}

// drawTransparentImage draws a transparent PNG of given dimensions
// and returns the PNG bytes.
func drawTransparentImage(h, w int) []byte {
	var (
		img = image.NewRGBA(image.Rect(0, 0, w, h))
		out = &bytes.Buffer{}
	)
	_ = png.Encode(out, img)
	return out.Bytes()
}