package classes

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"image"
	"io"
	"slices"
	"strconv"
	"strings"
	"time"

	"git.golem15.com/golem15/sm-journal-plugin/models"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/compass"
	"git.golem15.com/golem15/summercms/modules/conga"
	"git.golem15.com/golem15/summercms/modules/diary"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach/webp"
	"gocloud.dev/blob"
	"gocloud.dev/gcerrors"
	"gorm.io/gorm"
)

// The image variants job and its configuration (2026-10-28 image formats,
// D-85, P33-43).
const (
	// ImageVariantsKind is the conga job kind golem15.journal.image_variants.
	ImageVariantsKind = "golem15.journal.image_variants"
	// ImageWidthsKey is the config key of the variant widths, in pixels.
	ImageWidthsKey = "golem15.journal.image_widths"
	// ImageVariantsMode is the thumbnail mode of a variant: the exact size
	// of the original's aspect ratio at the variant's width.
	ImageVariantsMode = "exact"
	// FeaturedImagesField is the system_files field of a post's featured
	// images.
	FeaturedImagesField = "featured_images"
	// MinImageWidth and MaxImageWidth bound a configured width.
	MinImageWidth = 16
	MaxImageWidth = 4096
)

// variantsLog logs the image variants as component journal.
var variantsLog = diary.For("journal")

// DefaultImageWidths are the variant widths without configuration.
var DefaultImageWidths = []int{480, 800, 1200}

// ImageVariantsArgs are the arguments of the image variants job: the
// system_files ids of the featured images to make variants of.
type ImageVariantsArgs struct {
	FileIDs []uint `json:"file_ids"`
}

// Kind is the job kind, golem15.journal.image_variants.
func (ImageVariantsArgs) Kind() string { return ImageVariantsKind }

// ImageWidths reads golem15.journal.image_widths: a list of widths or a
// comma-separated text (an environment override), each 16 to 4096, sorted
// and once each. An unset, empty or invalid value answers
// DefaultImageWidths.
func ImageWidths(cfg *compass.Config) []int {
	if cfg == nil {
		return slices.Clone(DefaultImageWidths)
	}
	raw, ok := cfg.Lookup(ImageWidthsKey)
	if !ok || raw == nil {
		return slices.Clone(DefaultImageWidths)
	}
	var parts []string
	switch v := raw.(type) {
	case string:
		parts = strings.Split(v, ",")
	case []any:
		for _, item := range v {
			parts = append(parts, fmt.Sprint(item))
		}
	case []int:
		for _, n := range v {
			parts = append(parts, strconv.Itoa(n))
		}
	default:
		parts = []string{fmt.Sprint(v)}
	}
	var out []int
	for _, p := range parts {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		n, err := strconv.Atoi(p)
		if err != nil || n < MinImageWidth || n > MaxImageWidth {
			return slices.Clone(DefaultImageWidths)
		}
		out = append(out, n)
	}
	if len(out) == 0 {
		return slices.Clone(DefaultImageWidths)
	}
	slices.Sort(out)
	return slices.Compact(out)
}

// VariantsResult is what one run of GenerateImageVariants did.
type VariantsResult struct {
	Files   int
	Written int
	Skipped int
}

// maxHeaderBytes caps the bytes read for an original's size.
const maxHeaderBytes = 1 << 20

// sourceSize reads an original's size from its header; ok is false for a
// missing original, one that does not decode, or one over the thumbnailer's
// pixel limit (attach would store the broken-image picture for it).
func sourceSize(ctx context.Context, bucket *blob.Bucket, f attach.File) (w, h int, ok bool, err error) {
	r, err := bucket.NewReader(ctx, attach.BlobKey(f.DiskName), nil)
	if gcerrors.Code(err) == gcerrors.NotFound {
		return 0, 0, false, nil
	}
	if err != nil {
		return 0, 0, false, err
	}
	raw, err := io.ReadAll(io.LimitReader(r, maxHeaderBytes))
	closeErr := r.Close()
	if err != nil {
		return 0, 0, false, err
	}
	if closeErr != nil {
		return 0, 0, false, closeErr
	}
	cfg, _, err := image.DecodeConfig(bytes.NewReader(raw))
	if err != nil || cfg.Width <= 0 || cfg.Height <= 0 {
		return 0, 0, false, nil
	}
	if int64(cfg.Width)*int64(cfg.Height) > attach.MaxImagePixels {
		return 0, 0, false, nil
	}
	return cfg.Width, cfg.Height, true, nil
}

// GenerateImageVariants writes the variants of the files ids (D-85): for
// each width of widths no larger than the original's, the thumbnail at that
// width (attach.File.ThumbKey, mode exact, the original's aspect ratio) and
// its WebP copy (webp.Variant), recorded in golem15_journal_image_variants.
// A width that already has its row is skipped, so a second run writes
// nothing. A missing, undecodable or oversized original is skipped and
// logged. A storage or database error is returned (the job retries).
func GenerateImageVariants(ctx context.Context, db *gorm.DB, bucket *blob.Bucket, widths []int, ids []uint) (VariantsResult, error) {
	var out VariantsResult
	if db == nil || bucket == nil {
		return out, errors.New("journal: image variants need the database and the uploads bucket")
	}
	if len(ids) == 0 {
		return out, nil
	}
	var files []attach.File
	if err := db.WithContext(ctx).Where("id IN ?", ids).Order("id ASC").Find(&files).Error; err != nil {
		return out, err
	}
	for _, f := range files {
		out.Files++
		var have []int
		if err := db.WithContext(ctx).Model(&models.ImageVariant{}).Where("file_id = ?", f.ID).Pluck("width", &have).Error; err != nil {
			return out, err
		}
		var todo []int
		for _, w := range widths {
			if !slices.Contains(have, w) {
				todo = append(todo, w)
			}
		}
		if len(todo) == 0 {
			continue
		}
		sw, sh, ok, err := sourceSize(ctx, bucket, f)
		if err != nil {
			return out, fmt.Errorf("journal: read original %d: %w", f.ID, err)
		}
		if !ok {
			variantsLog.Warn("journal: no image variants for an unusable original", "file", f.ID)
			out.Skipped++
			continue
		}
		for _, w := range todo {
			if w > sw {
				out.Skipped++
				continue
			}
			h := max(1, int((int64(sh)*int64(w)+int64(sw)/2)/int64(sw)))
			if h > MaxImageWidth {
				// A tall original (an infographic): the variant would leave
				// the thumbnailer's edge limit, so this width is skipped like
				// one wider than the original, and the job goes on.
				variantsLog.Warn("journal: no image variant taller than the edge limit", "file", f.ID, "width", w, "height", h, "max", MaxImageWidth)
				out.Skipped++
				continue
			}
			key, err := f.ThumbKey(ctx, bucket, w, h, ImageVariantsMode)
			if err != nil {
				return out, fmt.Errorf("journal: thumbnail %d at %d: %w", f.ID, w, err)
			}
			webpKey, err := webp.Variant(ctx, bucket, &f, w, h, ImageVariantsMode)
			if err != nil {
				return out, fmt.Errorf("journal: webp %d at %d: %w", f.ID, w, err)
			}
			row := models.ImageVariant{FileID: f.ID, Width: w, Height: h, Key: key, WebPKey: webpKey, SourceWidth: sw, SourceHeight: sh, CreatedAt: time.Now().UTC()}
			res := db.WithContext(ctx).Exec(`INSERT INTO golem15_journal_image_variants (file_id, width, height, key, webp_key, source_width, source_height, created_at)
VALUES (?, ?, ?, ?, ?, ?, ?, ?) ON CONFLICT (file_id, width) DO NOTHING`, row.FileID, row.Width, row.Height, row.Key, row.WebPKey, row.SourceWidth, row.SourceHeight, row.CreatedAt)
			if res.Error != nil {
				return out, res.Error
			}
			out.Written += int(res.RowsAffected)
		}
	}
	return out, nil
}

// featuredFiles is the featured images of the posts, or of every post when
// postIDs is nil; missing is true to keep only the images without any
// variant row, or without a row for a width no larger than their original.
func featuredFiles(db *gorm.DB, postIDs []uint, widths []int, missing bool) ([]uint, error) {
	q := db.Model(&attach.File{}).Where("attachment_type = ? AND field = ?", (models.Post{}).MorphName(), FeaturedImagesField)
	if postIDs != nil {
		keys := make([]string, 0, len(postIDs))
		for _, id := range postIDs {
			keys = append(keys, strconv.FormatUint(uint64(id), 10))
		}
		q = q.Where("attachment_id IN ?", keys)
	}
	if missing {
		list := make([]string, 0, len(widths))
		for _, w := range widths {
			list = append(list, strconv.Itoa(w))
		}
		q = q.Where(`NOT EXISTS (SELECT 1 FROM golem15_journal_image_variants v WHERE v.file_id = system_files.id)
OR EXISTS (SELECT 1 FROM unnest(?::int[]) AS w(width)
	WHERE w.width <= (SELECT MAX(v.source_width) FROM golem15_journal_image_variants v WHERE v.file_id = system_files.id)
	AND NOT EXISTS (SELECT 1 FROM golem15_journal_image_variants v WHERE v.file_id = system_files.id AND v.width = w.width))`, "{"+strings.Join(list, ",")+"}")
	}
	var ids []uint
	err := q.Order("id ASC").Pluck("id", &ids).Error
	return ids, err
}

// FeaturedImageIDs lists the featured images of every post (all) or only
// those missing a variant of a configured width no larger than their
// original (or without any variant yet).
func FeaturedImageIDs(db *gorm.DB, cfg *compass.Config, all bool) ([]uint, error) {
	return featuredFiles(db, nil, ImageWidths(cfg), !all)
}

// DispatchImageVariants queues the image variants job for the files ids.
// The upload or save that called it has committed; a queue that cannot
// take the job is logged and never fails that request (D-85).
func DispatchImageVariants(ctx context.Context, app *backpack.App, ids []uint) {
	if app == nil || len(ids) == 0 {
		return
	}
	m, err := conga.From(app)
	if err == nil {
		_, err = m.Dispatch(ctx, nil, ImageVariantsArgs{FileIDs: ids}, conga.DispatchOpts{Label: "Journal image variants"})
	}
	if err != nil {
		variantsLog.Warn("journal: image variants job not queued", "files", len(ids), "error", err)
	}
}

// DispatchPostImageVariantsAfterCommit queues the image variants job, once
// tx commits, for the post's featured images that lack a variant of some
// width (the admin save: the uploads it binds commit with it).
func DispatchPostImageVariantsAfterCommit(ctx context.Context, tx *gorm.DB, app *backpack.App, postID uint) {
	if app == nil || postID == 0 {
		return
	}
	lagoon.AfterCommit(ctx, tx, func(ctx context.Context, _ *gorm.DB) {
		db, ok := app.Lookup[*gorm.DB]()
		if !ok || db == nil {
			return
		}
		ids, err := featuredFiles(db.WithContext(ctx), []uint{postID}, ImageWidths(app.Config), true)
		if err != nil {
			variantsLog.Warn("journal: image variants of a saved post", "post", postID, "error", err)
			return
		}
		DispatchImageVariants(ctx, app, ids)
	})
}