package classes

import (
	"context"
	"errors"
	"fmt"
	"strconv"
	"time"

	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"git.golem15.com/jakub/sm-bm-plugin/models"
	"gocloud.dev/blob"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// EnsureFileTexts extracts the text of every current public PDF of material
// materialID that has no text row yet, and stores one row per file (an
// empty text for a scan or a broken PDF, so it is not retried). It returns
// how many rows it added. ErrPDFToolMissing stops the loop and is returned
// as is, so callers can match it; a blob, extraction or insert error is
// returned wrapped with the file id. It runs only in the extraction job and
// bm:materials-reindex, never in a request.
func EnsureFileTexts(ctx context.Context, db *gorm.DB, bucket *blob.Bucket, pdf PDFText, materialID uint) (int, error) {
	if db == nil {
		return 0, fmt.Errorf("jz.bm: no database for the file texts of material %d", materialID)
	}
	if bucket == nil {
		return 0, fmt.Errorf("jz.bm: no uploads bucket for the file texts of material %d", materialID)
	}
	db = db.WithContext(ctx)
	// The conditions of the API's materialFiles, which classes cannot import.
	var files []attach.File
	err := db.Model(&attach.File{}).
		Select("system_files.*").
		Joins("LEFT JOIN jz_bm_material_file_texts t ON t.file_id = system_files.id").
		Where("system_files.attachment_type = ? AND system_files.attachment_id = ? AND system_files.field = ?",
			models.Material{}.MorphName(), strconv.FormatUint(uint64(materialID), 10), models.MaterialFilesField).
		Where("system_files.is_public").
		Where("(system_files.content_type = 'application/pdf' OR lower(system_files.file_name) LIKE '%.pdf')").
		Where("t.file_id IS NULL").
		Order("system_files.sort_order NULLS LAST, system_files.id").
		Find(&files).Error
	if err != nil {
		return 0, err
	}
	added := 0
	for _, f := range files {
		text, truncated, err := extractBlob(ctx, bucket, pdf, f)
		if errors.Is(err, ErrPDFToolMissing) {
			return added, err
		}
		if err != nil {
			return added, fmt.Errorf("jz.bm: file %d: %w", f.ID, err)
		}
		row := models.MaterialFileText{FileID: f.ID, MaterialID: materialID, Text: text, Truncated: truncated, ExtractedAt: time.Now().UTC()}
		res := db.Clauses(clause.OnConflict{Columns: []clause.Column{{Name: "file_id"}}, DoNothing: true}).Create(&row)
		if res.Error != nil {
			return added, fmt.Errorf("jz.bm: file %d: %w", f.ID, res.Error)
		}
		if res.RowsAffected > 0 {
			added++
		}
	}
	return added, nil
}

// extractBlob runs pdf on the blob of f.
func extractBlob(ctx context.Context, bucket *blob.Bucket, pdf PDFText, f attach.File) (string, bool, error) {
	rd, err := bucket.NewReader(ctx, attach.BlobKey(f.DiskName), nil)
	if err != nil {
		return "", false, err
	}
	defer rd.Close()
	return pdf.Extract(ctx, rd)
}