package api

import (
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"git.golem15.com/golem15/summercms/modules/surf"
	"git.golem15.com/jakub/sm-bm-plugin/models"
	"gorm.io/gorm"
)

// published scopes a material query to what students may see: a
// publication time that has passed. A NULL published_at is a draft.
func published(q *gorm.DB, now time.Time) *gorm.DB {
	return q.Where("jz_bm_materials.published_at IS NOT NULL AND jz_bm_materials.published_at <= ?", now.UTC())
}

// materialFilter holds the validated filters of /materials.
type materialFilter struct {
	CourseID uint
	Tag      string
	Type     string
}

func (f materialFilter) apply(q *gorm.DB) *gorm.DB {
	if f.CourseID != 0 {
		q = q.Where("jz_bm_materials.course_id = ?", f.CourseID)
	}
	if f.Type != "" {
		q = q.Where("jz_bm_materials.type = ?", f.Type)
	}
	if f.Tag != "" {
		q = q.Where(`EXISTS (SELECT 1 FROM jz_bm_material_tag mt JOIN jz_bm_tags t ON t.id = mt.tag_id
WHERE mt.material_id = jz_bm_materials.id AND t.slug = ?)`, f.Tag)
	}
	return q
}

func preloadMaterial(q *gorm.DB) *gorm.DB {
	return q.Preload("Course").Preload("Tags", func(db *gorm.DB) *gorm.DB { return db.Order("jz_bm_tags.name") })
}

// listMaterials returns one page of published materials, newest first.
func listMaterials(db *gorm.DB, now time.Time, f materialFilter, page, perPage int) ([]materialListJSON, int64, error) {
	q := f.apply(published(db.Model(&models.Material{}), now))
	var total int64
	if err := q.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var rows []models.Material
	err := preloadMaterial(f.apply(published(db, now))).
		Order("jz_bm_materials.published_at DESC, jz_bm_materials.id DESC").
		Offset((page - 1) * perPage).Limit(perPage).
		Find(&rows).Error
	if err != nil {
		return nil, 0, err
	}
	out, err := materialsJSON(db, rows)
	return out, total, err
}

// materialsJSON builds list rows with their file counts.
func materialsJSON(db *gorm.DB, rows []models.Material) ([]materialListJSON, error) {
	ids := make([]string, 0, len(rows))
	for _, m := range rows {
		ids = append(ids, strconv.FormatUint(uint64(m.ID), 10))
	}
	counts := map[string]int64{}
	if len(ids) > 0 {
		var found []struct {
			AttachmentID string
			Count        int64
		}
		err := db.Model(&attach.File{}).
			Select("attachment_id, COUNT(*) AS count").
			Where("attachment_type = ? AND field = ? AND is_public AND attachment_id IN ?", models.Material{}.MorphName(), models.MaterialFilesField, ids).
			Group("attachment_id").
			Scan(&found).Error
		if err != nil {
			return nil, err
		}
		for _, row := range found {
			counts[row.AttachmentID] = row.Count
		}
	}
	out := make([]materialListJSON, 0, len(rows))
	for _, m := range rows {
		out = append(out, newMaterialListJSON(m, counts[strconv.FormatUint(uint64(m.ID), 10)]))
	}
	return out, nil
}

// Materials answers GET /materials?course=&tag=&type=&page=&per_page=: a
// page of published materials in the {data, meta} shape of lagoon.Paginate.
func (h *Handlers) Materials(w http.ResponseWriter, r *http.Request) {
	if _, ok := h.caller(w, r); !ok {
		return
	}
	in := query(r, "course", "tag", "type", "page", "per_page")
	if !h.validate(w, r, in, materialsRules) {
		return
	}
	db, ok := h.db(w, r)
	if !ok {
		return
	}
	filter := materialFilter{CourseID: uintParam(in, "course"), Tag: strings.TrimSpace(str(in, "tag")), Type: str(in, "type")}
	page := min(intParam(in, "page", 1), 100000)
	perPage := intParam(in, "per_page", h.perPage())
	rows, total, err := listMaterials(db, h.now(), filter, page, perPage)
	if err != nil {
		writeOpaque500(w)
		return
	}
	writeJSONPage(w, lagoon.Paginate(rows, page, perPage, total))
}

// Material answers GET /materials/{id}: one published material with its
// body, tags and files. A draft or a future publication is a 404.
func (h *Handlers) Material(w http.ResponseWriter, r *http.Request) {
	if _, ok := h.caller(w, r); !ok {
		return
	}
	db, ok := h.db(w, r)
	if !ok {
		return
	}
	id, ok := surf.IntParam(r, "id")
	if !ok {
		writeNotFound(w)
		return
	}
	var m models.Material
	res := preloadMaterial(published(db, h.now())).Where("jz_bm_materials.id = ?", id).Limit(1).Find(&m)
	if res.Error != nil {
		writeOpaque500(w)
		return
	}
	if res.RowsAffected == 0 {
		writeNotFound(w)
		return
	}
	var files []attach.File
	err := db.Where("attachment_type = ? AND attachment_id = ? AND field = ?", m.MorphName(), strconv.FormatUint(uint64(m.ID), 10), models.MaterialFilesField).
		Order("sort_order, id").
		Find(&files).Error
	if err != nil {
		writeOpaque500(w)
		return
	}
	out := materialDetailJSON{
		materialListJSON: newMaterialListJSON(m, int64(len(files))),
		Body:             m.Body,
		Files:            make([]fileJSON, 0, len(files)),
	}
	for i := range files {
		f := &files[i]
		if !f.Public() {
			continue
		}
		out.Files = append(out.Files, fileJSON{ID: f.ID, URL: f.URL(), Name: f.FileName, Size: f.FileSize, Mime: f.ContentType})
	}
	out.FilesCount = int64(len(out.Files))
	writeData(w, out)
}

// publishedMaterialsOfCourse lists a course's published materials, newest
// first, for /courses/{id}.
func publishedMaterialsOfCourse(db *gorm.DB, now time.Time, courseID uint) ([]materialListJSON, error) {
	var rows []models.Material
	err := preloadMaterial(published(db, now)).
		Where("jz_bm_materials.course_id = ?", courseID).
		Order("jz_bm_materials.published_at DESC, jz_bm_materials.id DESC").
		Find(&rows).Error
	if err != nil {
		return nil, err
	}
	return materialsJSON(db, rows)
}