// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package ofdgo

import (
	"context"
	"fmt"
	"image"
	"math"
)

// compressionImages 记录图片各处使用的最大像素需求
type compressionImages struct {
	ctx           context.Context
	dpi           int
	sizes         map[string]image.Point
	renderer      *Renderer
	patternPage   *Matrix
	patterns      map[*Pattern]bool
	patternVisits map[compressionPatternKey]bool
}

// compressionImagePlan 为有损输出分文档分析图片，按共享路径合并最大尺寸和保护条件
// 入参: ctx 取消上下文, options 压缩配置
// 返回: map[string]bool 可有损处理的路径, map[string]image.Point 像素需求, error 读取或取消错误
func (r *Reader) compressionImagePlan(ctx context.Context, options CompressionOptions) (map[string]bool, map[string]image.Point, error) {
	if options.Mode != CompressionLossy {
		return nil, nil, ctx.Err()
	}
	images := make(map[string]bool)
	sizes := make(map[string]image.Point)
	blocked := make(map[string]bool)
	for index := 0; index < r.DocumentCount(); index++ {
		if err := ctx.Err(); err != nil {
			return nil, nil, err
		}
		document := r
		if index != r.DocumentIndex() {
			var err error
			document, err = r.DocumentContext(ctx, index)
			if err != nil {
				return nil, nil, err
			}
		}
		catalog, err := document.Images(ctx)
		if err != nil {
			if document != r {
				document.Close()
			}
			return nil, nil, err
		}
		if len(catalog) == 0 {
			if document != r {
				document.Close()
			}
			continue
		}
		var demands map[string]image.Point
		masks, geometry, err := document.compressionImageSafety(ctx, catalog)
		if err == nil && geometry {
			demands, err = document.compressionImageSizes(ctx, catalog, options.ImageDPI())
		}
		if document != r {
			document.Close()
		}
		if err != nil {
			return nil, nil, err
		}
		for _, img := range catalog {
			name := cleanPackagePath(img.Location)
			if old, ok := images[name]; !ok || old {
				images[name] = !masks[name]
			}
			size := demands[name]
			if size.X <= 0 || size.Y <= 0 || masks[name] {
				blocked[name] = true
				delete(sizes, name)
				continue
			}
			if !blocked[name] {
				old := sizes[name]
				sizes[name] = image.Pt(max(old.X, size.X), max(old.Y, size.Y))
			}
		}
	}
	return images, sizes, ctx.Err()
}

// compressionImageSize 将毫米显示尺寸换算为像素，非法尺寸不降采样
// 整像素边界消除单位换算产生的单ULP上溢，不降低实际像素需求
// 入参: width 显示宽度, height 显示高度, dpi 分辨率上限
// 返回: image.Point 像素需求
func compressionImageSize(width, height float64, dpi int) image.Point {
	w := math.Ceil(math.Nextafter(width*float64(dpi)/25.4, math.Inf(-1)))
	h := math.Ceil(math.Nextafter(height*float64(dpi)/25.4, math.Inf(-1)))
	if w <= 0 || h <= 0 || math.IsNaN(w) || math.IsNaN(h) || math.IsInf(w, 0) || math.IsInf(h, 0) || w > 1<<30 || h > 1<<30 {
		return image.Point{}
	}
	return image.Pt(int(w), int(h))
}

// compressionImageSizes 按正文、模板、注解及底纹的实际变换汇总图片尺寸，包括隐藏内容
// 入参: ctx 取消上下文, images 图片资源, dpi 分辨率上限
// 返回: map[string]image.Point 资源像素需求, error 取消错误
func (r *Reader) compressionImageSizes(ctx context.Context, images []ImageInfo, dpi int) (map[string]image.Point, error) {
	if dpi == 0 {
		return nil, nil
	}
	doc, err := r.DocContext(ctx)
	if err != nil {
		return nil, ctx.Err()
	}
	renderer := NewRenderer(r, WithRenderBackends(RenderBackends{}))
	renderer.pageContext = ctx
	defer renderer.ClearCache()
	visitor := &compressionImages{ctx: ctx, dpi: dpi, sizes: make(map[string]image.Point), renderer: renderer}
	for _, ref := range doc.Pages.Page {
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		page, err := r.PageContentContext(ctx, ref)
		if err != nil {
			return nil, ctx.Err()
		}
		for _, ref := range page.Template {
			if renderer.loadTemplate(ref.TemplateID) == nil {
				return nil, ctx.Err()
			}
		}
		if err := renderer.WalkPage(page, visitor); err != nil {
			return nil, ctx.Err()
		}
	}
	for _, ref := range r.doc.CommonData.TemplatePage {
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		template := renderer.loadTemplate(ref.ID)
		if template == nil {
			return nil, ctx.Err()
		}
		for order := range 3 {
			if err := renderer.walkLayers(template.Content.Layer, order, visitor); err != nil {
				return nil, ctx.Err()
			}
		}
	}
	result := make(map[string]image.Point)
	for _, img := range images {
		name := cleanPackagePath(img.Location)
		size := visitor.sizes[editorResourceID(img.ID)]
		old := result[name]
		result[name] = image.Pt(max(old.X, size.X), max(old.Y, size.Y))
	}
	return result, ctx.Err()
}

// DrawObject 汇总图片、替换图及文字、路径和图像边框底纹的尺寸，不使用裁剪后的局部面积
// 入参: object 图形对象, state 继承状态
// 返回: error 取消或几何错误
func (v *compressionImages) DrawObject(object *GraphicObject, state RenderState) error {
	if err := v.ctx.Err(); err != nil {
		return err
	}
	switch object.Type {
	case "PathObject":
		return v.objectPatterns(object.PathObject, state)
	case "TextObject":
		text := object.TextObject
		return v.objectPatterns(PathObject{Boundary: text.Boundary, CTM: text.CTM, DrawParam: text.DrawParam, FillColor: text.FillColor, StrokeColor: text.StrokeColor}, state)
	case "ImageObject":
	default:
		return nil
	}
	img := object.ImageObject
	ids := [2]string{editorResourceID(img.ResourceID), editorResourceID(img.Substitution)}
	if ids[0] == "" || img.Substitution != "" && ids[1] == "" {
		return fmt.Errorf("invalid image resource")
	}
	box, err := ParseBox(img.Boundary)
	if err != nil {
		return err
	}
	if border := img.Border; border != nil && border.BorderColor != nil && border.BorderColor.Pattern != nil {
		matrix, _ := renderObjectMatrix(img.Boundary, IdentityMatrix, state)
		if err := v.patternImages((*FillColor)(border.BorderColor), matrix); err != nil {
			return err
		}
	}
	local := NewMatrix(img.CTM)
	if img.CTM == "" {
		local = Matrix{a: box.W, d: box.H}
	}
	matrix, _ := renderObjectMatrix(img.Boundary, local, state)
	size := compressionImageSize(math.Hypot(matrix.a, matrix.b), math.Hypot(matrix.c, matrix.d), v.dpi)
	return v.recordSize(ids, size)
}

// VisitComposite 按矢量资源的完整变换统计缩略图和替换图，不以裁剪区域缩减尺寸
// 入参: object 矢量资源或复合图元, state 已包含当前图元变换的状态
// 返回: error 取消、资源标识或几何错误
func (v *compressionImages) VisitComposite(object *CompositeGraphicUnit, state RenderState) error {
	if err := v.ctx.Err(); err != nil {
		return err
	}
	if object.Thumbnail == "" && object.Substitution == "" {
		return nil
	}
	ids := [2]string{editorResourceID(object.Thumbnail), editorResourceID(object.Substitution)}
	if object.Thumbnail != "" && ids[0] == "" || object.Substitution != "" && ids[1] == "" {
		return fmt.Errorf("invalid composite image resource")
	}
	matrix := IdentityMatrix
	if state.Parent != nil {
		matrix = *state.Parent
	}
	size := compressionImageSize(object.Width*math.Hypot(matrix.a, matrix.b), object.Height*math.Hypot(matrix.c, matrix.d), v.dpi)
	return v.recordSize(ids, size)
}

// recordSize 合并同一图像资源在不同位置的最大像素需求
// 入参: ids 图像标识，空值不统计, size 当前像素需求
// 返回: error 尺寸无效时返回错误
func (v *compressionImages) recordSize(ids [2]string, size image.Point) error {
	if size.X == 0 || size.Y == 0 {
		return fmt.Errorf("invalid image placement")
	}
	for _, id := range ids {
		if id == "" {
			continue
		}
		old := v.sizes[id]
		v.sizes[id] = image.Pt(max(old.X, size.X), max(old.Y, size.Y))
	}
	return nil
}

// DrawStamp 保留签章内容，不参与图片降采样
// 入参: stamp 印章
// 返回: error 始终为空
func (v *compressionImages) DrawStamp(stamp Stamp) error { return nil }

// IncludeHidden 将隐藏内容纳入尺寸分析，保留图片在所有使用位置的精度
// 返回: bool 始终为真
func (v *compressionImages) IncludeHidden() bool { return true }

// SkipClips 按完整图片尺寸分析，不加载裁剪几何或文字轮廓
// 返回: bool 始终为真
func (v *compressionImages) SkipClips() bool { return true }