package analyticsApi

import (
	"encoding/json"
	"git.stuve.uni-ulm.de/stuve-it/stuve-it-backend/ldapApi"
	"git.stuve.uni-ulm.de/stuve-it/stuve-it-backend/logger"
	"github.com/labstack/echo/v5"
	"github.com/pocketbase/dbx"
	"github.com/pocketbase/pocketbase"
	"github.com/pocketbase/pocketbase/apis"
	"github.com/pocketbase/pocketbase/core"
	"strconv"
	"time"
)

// initPageViewCount
//
// This endpoint is used to retrieve paginated page view counts for each unique path.
// It adds the following endpoint to the app:
// GET /api/analytics/pageViewCount
//
// Query parameters:
//
//	?startDate=ISO 8601 formatted date (optional)
//	?page=<page number>
//	?perPage=<results per page>
//	?sort=<ASC|DESC> (default is ASC)
//
// - `startDate`: Optional start date in ISO 8601 format (e.g., "2024-11-12T15:04:05Z").
// - `page`: Page number for pagination (default is 1).
// - `perPage`: Number of results per page (default is 10).
// - `sort`: Sorting order, either `ASC` or `DESC` (default is ASC).
//
// Response format:
//
//	{
//	  "page": <current page number>,
//	  "perPage": <results per page>,
//	  "totalItems": <total number of items matching the filter>,
//	  "totalPages": <total number of pages>,
//	  "items": [
//	    {
//	      "id": <unique row id>,
//	      "path": "<path>",
//	      "count": <total view count since startDate>,
//	      "last_30_days_data": [
//	        {
//	          "date": "YYYY-MM-DDTHH:MM:SSZ",
//	          "count": <daily count>
//	        },
//	        ...
//	      ]
//	    },
//	    ...
//	  ]
//	}
func initPageViewCount(app *pocketbase.PocketBase, e *core.ServeEvent) {

	e.Router.GET("/api/analytics/pageViewCount", func(c echo.Context) error {

		// Check if user is in admin group
		if err := ldapApi.UserIsInAdminGroup(app, c); err != nil {
			return err
		}

		// Get startDate from query parameter
		startDateParam := c.QueryParam("startDate")
		var startDate time.Time
		var err error
		if startDateParam != "" {
			startDate, err = time.Parse(time.RFC3339, startDateParam)
			if err != nil {
				return apis.NewBadRequestError("Invalid start date format, expected ISO 8601", err)
			}
		} else {
			// Default to the beginning of time if not provided
			startDate = time.Time{}
		}

		// Pagination and sorting parameters
		page, _ := strconv.Atoi(c.QueryParam("page"))
		if page < 1 {
			page = 1
		}

		perPage, _ := strconv.Atoi(c.QueryParam("perPage"))
		if perPage < 1 {
			perPage = 10
		}

		sort := c.QueryParam("sort")
		if sort != "ASC" && sort != "DESC" {
			sort = "DESC" // default sorting order
		}

		offset := (page - 1) * perPage

		// Fetch total items for pagination
		var totalItems int
		err = app.Dao().DB().
			NewQuery(`
				SELECT COUNT(DISTINCT path) as total
				FROM analyticsPageViews
				WHERE created >= {:startDate}
			`).
			Bind(dbx.Params{
				"startDate": startDate.Format("2006-01-02 15:04:05"),
			}).
			Row(&totalItems)

		if err != nil {
			return apis.NewApiError(500, "Failed to count total items", err)
		}

		totalPages := (totalItems + perPage - 1) / perPage // Calculate total pages

		// Define the structure for items
		type Last30DaysData struct {
			Date  string `json:"date"`
			Count int    `json:"count"`
		}

		type Item struct {
			Path           string           `json:"path"`
			Count          int              `json:"count"`
			Last30DaysData []Last30DaysData `json:"last_30_days_data"`
		}

		// Query paginated items
		var rawItems []struct {
			Path           string `db:"path" json:"path"`
			Count          int    `db:"count" json:"count"`
			Last30DaysData string `db:"last_30_days_data" json:"last_30_days_data"` // JSON string to parse
		}

		err = app.Dao().DB().
			NewQuery(`
				SELECT 
					view.path,
					COUNT(view.id) AS count,
					(
						SELECT json_group_array(
							json_object(
								'date', date,
								'count', daily_count
							)
						)
						FROM (
							SELECT 
								strftime('%Y-%m-%d', created) AS date,
								COUNT(id) AS daily_count
							FROM analyticsPageViews
							WHERE 
								path = view.path 
								AND created >= datetime('now', '-30 days')
							GROUP BY date
						) AS daily_data
					) AS last_30_days_data
				FROM analyticsPageViews AS view
				WHERE view.created >= {:startDate}
				GROUP BY view.path
				ORDER BY count ` + sort + `
				LIMIT {:perPage} OFFSET {:offset}
			`).
			Bind(dbx.Params{
				"startDate": startDate.Format("2006-01-02 15:04:05"),
				"perPage":   perPage,
				"offset":    offset,
			}).
			All(&rawItems)

		if err != nil {
			return apis.NewApiError(500, "Failed to query page view data", err)
		}

		// Parse last_30_days_data JSON string into structured data
		var items []Item
		for _, rawItem := range rawItems {
			var last30DaysData []Last30DaysData
			if rawItem.Last30DaysData != "" {
				if err := json.Unmarshal([]byte(rawItem.Last30DaysData), &last30DaysData); err != nil {
					return apis.NewApiError(500, "Failed to parse last_30_days_data", err)
				}
			}

			items = append(items, Item{
				Path:           rawItem.Path,
				Count:          rawItem.Count,
				Last30DaysData: last30DaysData,
			})
		}

		// Final response structure
		response := map[string]interface{}{
			"page":       page,
			"perPage":    perPage,
			"totalItems": totalItems,
			"totalPages": totalPages,
			"items":      items,
		}

		// Return the final JSON response
		return c.JSON(200, response)
	}, apis.ActivityLogger(app))
}

// initAggregateCount
//
// This endpoint is used to aggregate session metadata counts by various categories
// (device type, browser name, operating system, user agent, geo country code, and preferred language).
// It adds the following endpoint to the app:
// GET /api/analytics/sessionCounts
//
// The endpoint expects the following query parameter:
//
//		?startDate=ISO 8601 formatted date (optional)
//
//	  - `startDate`: An optional start date in ISO 8601 format (e.g., "2024-11-12T15:04:05Z").
//	    If provided, counts reflect sessions from this date onward.
//	    If not provided, counts include all sessions.
//
// Response format:
//
//	{
//	  "device_type": [
//	    { "value": "<device type>", "count": <session count>, "error_count": <error count>, "success_count": <success count> },
//	    ...
//	  ],
//	  "browser_name": [
//	    { "value": "<browser name>", "count": <session count>, "error_count": <error count>, "success_count": <success count> },
//	    ...
//	  ],
//	  "operating_system": [
//	    { "value": "<operating system>", "count": <session count>, "error_count": <error count>, "success_count": <success count> },
//	    ...
//	  ],
//	  "user_agent": [
//	    { "value": "<user agent>", "count": <session count>, "error_count": <error count>, "success_count": <success count> },
//	    ...
//	  ],
//	  "geo_country_code": [
//	    { "value": "<country code>", "count": <session count>, "error_count": <error count>, "success_count": <success count> },
//	    ...
//	  ],
//	  "preferred_language": [
//	    { "value": "<preferred language>", "count": <session count>, "error_count": <error count>, "success_count": <success count> },
//	    ...
//	  ]
//	}
//
// Each category includes an array of objects where `value` is the specific item (e.g., a device type or browser name),
// `count` is the total number of sessions matching that item since `startDate`, and `error_count` is the number
// of sessions with errors for that item (where the `error` field is not NULL) since `startDate`.
func initAggregateCount(app *pocketbase.PocketBase, e *core.ServeEvent) {
	e.Router.GET("/api/analytics/aggregateCount", func(c echo.Context) error {

		// Check if user is in admin group
		if err := ldapApi.UserIsInAdminGroup(app, c); err != nil {
			return err
		}

		// Parse the start date
		startDate, err := time.Parse(time.RFC3339, c.QueryParam("startDate"))
		if err != nil {
			return apis.NewBadRequestError("Invalid start date format, expected ISO 8601", err)
		}

		type Data struct {
			Value        string `db:"value" json:"value"`
			Count        int    `db:"count" json:"count"`
			SuccessCount int    `db:"success_count" json:"success_count"`
			ErrorCount   int    `db:"error_count" json:"error_count"`
		}

		// Use a map to store the response data
		response := make(map[string][]Data)

		fields := []string{"device_type", "browser_name", "operating_system", "geo_country_code", "preferred_language"}

		for _, field := range fields {
			data := []Data{}

			err := app.Dao().DB().
				NewQuery(`
					SELECT 
						IFNULL(` + field + `, 'N/A') as value, 
						COUNT(id) AS count,
						SUM(CASE WHEN error IS NULL THEN 1 ELSE 0 END) AS success_count,
						SUM(CASE WHEN error IS NOT NULL THEN 1 ELSE 0 END) AS error_count
					FROM analyticsPageViewsWithSessionDetail
					WHERE created >= {:startDate}
					GROUP BY ` + field).
				Bind(dbx.Params{
					"startDate": startDate,
				}).
				All(&data)

			if err != nil {
				return apis.NewApiError(500, "Failed to aggregate data for "+field, err)
			}

			// Assign the data to the corresponding field in the map
			response[field] = data
		}

		// Return the final JSON response
		return c.JSON(200, response)
	}, apis.ActivityLogger(app))
}

// InitAnalyticsApi initializes analytics api endpoints
func InitAnalyticsApi(app *pocketbase.PocketBase, e *core.ServeEvent) error {

	logger.LogInfoF("Initializing analytics api")

	initPageViewCount(app, e)
	initAggregateCount(app, e)

	return nil
}