import QtQuick 2.15
import QtQuick.Layouts 1.15
import QtQuick.Controls 2.15

import org.kde.plasma.plasmoid 2.0
import org.kde.plasma.core 2.0 as PlasmaCore
import org.kde.plasma.components 2.0 as PlasmaComponents
import org.kde.plasma.components 3.0 as PlasmaComponents3
import org.kde.plasma.extras 2.0 as PlasmaExtras

Item {
    width: PlasmaCore.Units.gridUnit * 20
    height: PlasmaCore.Units.gridUnit * 40
    clip: true

    readonly property string canvasUrl: plasmoid.configuration.canvasUrl
    readonly property string apiEndpoint: `${canvasUrl.replace(/\/$/, "")}/api/v1`
    readonly property string oauth2Token: plasmoid.configuration.oauth2Token
    readonly property string authHeader: `Bearer ${oauth2Token}`

    function callApi(path, perPage, callback) {
        let xhr = new XMLHttpRequest()
        let apiUrl = `${apiEndpoint}${path}`
        if (perPage >= 1) {
            // add pagination parameter
            apiUrl += `${path.includes("?") ? "&" : "?"}per_page=${perPage}`
        }
        xhr.open("GET", apiUrl)
        xhr.setRequestHeader("Authorization", authHeader)
        xhr.onload = () => {
            if (xhr.status == 200) {
                try {
                    let json = JSON.parse(xhr.responseText)
                    if (callback) { callback(json) }
                } catch (e) {
                    if (e instanceof SyntaxError) {
                        console.error(`Cannot parse response for ${path} as JSON:\n${xhr.responseText}`)
                    } else { throw e }
                }
            } else {
                console.error(`XHR failed when retrieving ${path} (status ${xhr.status}):\n${xhr.responseText}`)
            }
        }
        xhr.send()
    }

    function syncCanvas() {
        const courses = plasmoid.configuration.courses.split("\n").map(
            // each line in the "courses" config consists of
            // a numeric course id, a space, and a course code
            line => {
                const spaceIndex = line.indexOf(" ")
                return {id: line.slice(0, spaceIndex), code: line.slice(spaceIndex + 1)}
            }
        )
        let courseIndices = {} // reverse look-up table to sort by courses
        for (let i = 0; i < courses.length; i++) {
            courseIndices[courses[i].id] = i
        }

        const showSubmittedAssignments = plasmoid.configuration.showSubmittedAssignments

        // we need user id to check submission status
        callApi("/users/self", 0, user => {
            syncCourses(courses, courseIndices, showSubmittedAssignments, user.id)
        })
    }

    // fetch asynchronously, but display in this order:
    // important -> normal -> finished
    // when an activity is both important and finished, important takes priority
    function syncCourses(courses, courseIndices, showSubmittedAssignments, userId) {
        announcementsModel.clear()
        assignmentsModel.clear()

        let announcementIndices = {
            important: 0, // actually constant, kept for symmetry
            normal: 0,
            finished: 0,
        }
        let assignmentIndices = {
            important: 0,
            normal: 0,
            finished: 0,
        }

        for (let course of courses) {
            const courseIdx = courseIndices[course.id]
            callApi(`/announcements?context_codes[]=course_${course.id}`, 50, announcements => {
                announcements.forEach(announcement => {
                    const info = {
                        type: "announcement",
                        activityId: announcement.id,
                        courseId: course.id,
                        course: course.code,
                        title: announcement.title,
                        url: announcement.html_url,
                        important: plasmoid.configuration.importantAnnouncements.includes(announcement.id.toString()),
                        finished: plasmoid.configuration.finishedAnnouncements.includes(announcement.id.toString()),
                    }

                    // figure out where we insert it into list
                    let idx = 0;
                    let endIdx = 0; // actually past the end
                    if (info.important) {
                        idx = announcementIndices.important
                        endIdx = announcementIndices.normal
                        announcementIndices.normal++
                        announcementIndices.finished++
                    } else if (!info.finished) {
                        idx = announcementIndices.normal
                        endIdx = announcementIndices.finished
                        announcementIndices.finished++
                    } else {
                        idx = announcementIndices.finished
                        endIdx = announcementsModel.count
                    }

                    for (; idx < endIdx; idx++) {
                        const annc = announcementsModel.get(idx)
                        if (courseIndices[course.id] < courseIndices[annc.courseId]) {
                            // we are just past the end of this course
                            // insert this announcement here
                            break
                        }
                    }
                    announcementsModel.insert(idx, info)
                })
            })

            callApi(`/courses/${course.id}/assignments`, 50, assignments => {
                assignments.forEach(assignment => {
                    callApi(`/courses/${course.id}/assignments/${assignment.id}/submissions/${userId}`, 0, submission => {
                        const submitted = submission.workflow_state == "submitted" ||
                                          submission.workflow_state == "graded"
                        if (submitted && !showSubmittedAssignments) return // discard this

                        const info = {
                            type: "assignment",
                            activityId: assignment.id,
                            courseId: course.id,
                            course: course.code,
                            title: assignment.name,
                            dueAt: assignment.due_at || "", // if null, use empty string to suppress errors
                            submitted: submitted,
                            url: assignment.html_url,
                            important: plasmoid.configuration.importantAssignments.includes(assignment.id.toString()),
                            finished: plasmoid.configuration.finishedAssignments.includes(assignment.id.toString()),
                        }

                        let idx = 0;
                        let endIdx = 0;
                        if (info.important) {
                            idx = assignmentIndices.important
                            endIdx = assignmentIndices.normal
                            assignmentIndices.normal++
                            assignmentIndices.finished++
                        } else if (!info.finished) {
                            idx = assignmentIndices.normal
                            endIdx = assignmentIndices.finished
                            assignmentIndices.finished++
                        } else {
                            idx = assignmentIndices.finished
                            endIdx = assignmentsModel.count
                        }

                        for (; idx < endIdx; idx++) {
                            const annc = assignmentsModel.get(idx)
                            if (courseIndices[course.id] < courseIndices[annc.courseId]) {
                                break
                            }
                        }
                        assignmentsModel.insert(idx, info)
                    })
                })
            })
        }
    }

    // sync on initialization
    Component.onCompleted: syncCanvas()

    // update every refreshInterval minutes
    Timer {
        interval: plasmoid.configuration.refreshInterval * 60 * 1000
        running: true
        repeat: true
        onTriggered: syncCanvas()
    }

    // top level layout
    ColumnLayout {
        id: main
        anchors.fill: parent

        PlasmaExtras.Heading {
            level: 1
            text: "Kanvas"
        }

        PlasmaExtras.Heading {
            level: 2
            text: "Announcements"
        }

        ListModel {
            id: announcementsModel
            /* Uncomment when debugging layout
            ListElement {
                type: "announcement"
                course: "CS101"
                title: "Code quality"
                url: "https://xkcd.com/1513"
                important: true
                finished: false
                activityId: 0
            }
            */
        }

        ScrollView {
            implicitHeight: PlasmaCore.Units.gridUnit * 20
            Layout.margins: PlasmaCore.Units.smallSpacing
            Layout.fillWidth: true
            Layout.fillHeight: true
            ScrollBar.horizontal.policy: ScrollBar.AlwaysOff

            ListView {
                id: announcementsListView
                Layout.fillWidth: true
                spacing: PlasmaCore.Units.smallSpacing
                delegate: ActivityView {}
                model: announcementsModel
            }
        }

        PlasmaExtras.Heading {
            level: 2
            text: "Assignments"
        }

        ListModel {
            id: assignmentsModel
            /* Uncomment when debugging layout
            ListElement {
                type: "assignment"
                course: "EE201"
                title: "Circuit diagram"
                dueAt: "2022-04-10T15:59:59Z"
                submitted: true
                url: "https://xkcd.com/730"
                important: true
                finished: true
                activityId: 1
            }
            */
        }

        ScrollView {
            implicitHeight: PlasmaCore.Units.gridUnit * 20
            Layout.margins: PlasmaCore.Units.smallSpacing
            Layout.fillWidth: true
            Layout.fillHeight: true
            ScrollBar.horizontal.policy: ScrollBar.AlwaysOff

            ListView {
                id: assignmentsListView
                Layout.fillWidth: true
                spacing: PlasmaCore.Units.gridUnit
                delegate: ActivityView {}
                model: assignmentsModel
            }
        }

        PlasmaComponents3.Button {
            icon.name: "view-refresh"
            text: i18n("Refresh")
            onClicked: syncCanvas()
        }
    }
}