package encoding

import (
	"fmt"
	"log"
	"os/exec"
	"strconv"
	"strings"
)

const (
	// CRFH264 is the Constant Rate Factor for H.264 encoding (lower = higher quality, range 0-51)
	CRFH264 = 15
	// CRFAV1 is the Constant Rate Factor for AV1 encoding (lower = higher quality, range 0-63)
	CRFAV1 = 30
	// CRFVP9 is the Constant Rate Factor for VP9 encoding (lower = higher quality, range 0-63)
	CRFVP9 = 30
)

// tonemapFilter returns the appropriate filter for EXR input.
// For HDR preservation: converts linear RGB (EXR) to bt2020 YUV with HLG transfer function
// Uses zscale to properly convert colorspace from linear RGB to bt2020 YUV while preserving HDR range
// Step 1: Ensure format is gbrpf32le (linear RGB)
// Step 2: Convert transfer function from linear to HLG (arib-std-b67) with bt2020 primaries/matrix
// Step 3: Convert to YUV format
func tonemapFilter(useAlpha bool) string {
	// Convert from linear RGB (gbrpf32le) to HLG with bt709 primaries to match PNG appearance
	// Based on best practices: convert linear RGB directly to HLG with bt709 primaries
	// This matches PNG color appearance (bt709 primaries) while preserving HDR range (HLG transfer)
	// zscale uses numeric values:
	//   primaries: 1=bt709 (matches PNG), 9=bt2020
	//   matrix: 1=bt709, 9=bt2020nc, 0=gbr (RGB input)
	//   transfer: 8=linear, 18=arib-std-b67 (HLG)
	// Direct conversion: linear RGB -> HLG with bt709 primaries -> bt2020 YUV (for wider gamut metadata)
	// The bt709 primaries in the conversion match PNG, but we set bt2020 in metadata for HDR displays
	// Convert linear RGB to sRGB first, then convert to HLG
	// This approach: linear -> sRGB -> HLG -> bt2020
	// Fixes red tint by using sRGB conversion, preserves HDR range with HLG
	filter := "format=gbrpf32le,zscale=transferin=8:transfer=13:primariesin=1:primaries=1:matrixin=0:matrix=1:rangein=full:range=full,zscale=transferin=13:transfer=18:primariesin=1:primaries=9:matrixin=1:matrix=9:rangein=full:range=full"
	if useAlpha {
		return filter + ",format=yuva420p10le"
	}
	return filter + ",format=yuv420p10le"
}

// SoftwareEncoder implements software encoding (libx264, libaom-av1, libvpx-vp9).
type SoftwareEncoder struct {
	codec string
}

func (e *SoftwareEncoder) Name() string  { return "software" }
func (e *SoftwareEncoder) Codec() string { return e.codec }

func (e *SoftwareEncoder) Available() bool {
	return true // Software encoding is always available
}

func (e *SoftwareEncoder) BuildCommand(config *EncodeConfig) *exec.Cmd {
	// Use HDR pixel formats for EXR, SDR for PNG
	var pixFmt string
	var colorPrimaries, colorTrc, colorspace string
	if config.SourceFormat == "png" {
		// PNG: SDR format
		pixFmt = "yuv420p"
		if config.UseAlpha {
			pixFmt = "yuva420p"
		}
		colorPrimaries = "bt709"
		colorTrc = "bt709"
		colorspace = "bt709"
	} else {
		// EXR: Use HDR encoding if PreserveHDR is true, otherwise SDR (like PNG)
		if config.PreserveHDR {
			// HDR: Use HLG transfer with bt709 primaries to preserve HDR range while matching PNG color
			pixFmt = "yuv420p10le" // 10-bit to preserve HDR range
			if config.UseAlpha {
				pixFmt = "yuva420p10le"
			}
			colorPrimaries = "bt709"  // bt709 primaries to match PNG color appearance
			colorTrc = "arib-std-b67" // HLG transfer function - preserves HDR range, works on SDR displays
			colorspace = "bt709"      // bt709 colorspace to match PNG
		} else {
			// SDR: Treat as SDR (like PNG) - encode as bt709
			pixFmt = "yuv420p"
			if config.UseAlpha {
				pixFmt = "yuva420p"
			}
			colorPrimaries = "bt709"
			colorTrc = "bt709"
			colorspace = "bt709"
		}
	}

	var codecArgs []string
	switch e.codec {
	case "libaom-av1":
		codecArgs = []string{"-crf", strconv.Itoa(CRFAV1), "-b:v", "0", "-tiles", "2x2", "-g", "240"}
	case "libvpx-vp9":
		// VP9 supports alpha and HDR, use good quality settings
		codecArgs = []string{"-crf", strconv.Itoa(CRFVP9), "-b:v", "0", "-row-mt", "1", "-g", "240"}
	default:
		// H.264: Use High 10 profile for HDR EXR (10-bit), High profile for SDR
		if config.SourceFormat != "png" && config.PreserveHDR {
			codecArgs = []string{"-preset", "veryslow", "-crf", strconv.Itoa(CRFH264), "-profile:v", "high10", "-level", "5.2", "-tune", "film", "-keyint_min", "24", "-g", "240", "-bf", "2", "-refs", "4"}
		} else {
			codecArgs = []string{"-preset", "veryslow", "-crf", strconv.Itoa(CRFH264), "-profile:v", "high", "-level", "5.2", "-tune", "film", "-keyint_min", "24", "-g", "240", "-bf", "2", "-refs", "4"}
		}
	}

	args := []string{
		"-y",
		"-f", "image2",
		"-start_number", fmt.Sprintf("%d", config.StartFrame),
		"-framerate", fmt.Sprintf("%.2f", config.FrameRate),
		"-i", config.InputPattern,
		"-c:v", e.codec,
		"-pix_fmt", pixFmt,
		"-r", fmt.Sprintf("%.2f", config.FrameRate),
		"-color_primaries", colorPrimaries,
		"-color_trc", colorTrc,
		"-colorspace", colorspace,
		"-color_range", "tv",
	}

	// Add video filter for EXR: convert linear RGB based on HDR setting
	// PNG doesn't need any filter as it's already in sRGB
	if config.SourceFormat != "png" {
		var vf string
		if config.PreserveHDR {
			// HDR: Convert linear RGB -> sRGB -> HLG with bt709 primaries
			// This preserves HDR range while matching PNG color appearance
			vf = "format=gbrpf32le,zscale=transferin=8:transfer=13:primariesin=1:primaries=1:matrixin=0:matrix=1:rangein=full:range=full,zscale=transferin=13:transfer=18:primariesin=1:primaries=1:matrixin=1:matrix=1:rangein=full:range=full"
			if config.UseAlpha {
				vf += ",format=yuva420p10le"
			} else {
				vf += ",format=yuv420p10le"
			}
		} else {
			// SDR: Convert linear RGB (EXR) to sRGB (bt709) - simple conversion like Krita does
			// zscale: linear (8) -> sRGB (13) with bt709 primaries/matrix
			vf = "format=gbrpf32le,zscale=transferin=8:transfer=13:primariesin=1:primaries=1:matrixin=0:matrix=1:rangein=full:range=full"
			if config.UseAlpha {
				vf += ",format=yuva420p"
			} else {
				vf += ",format=yuv420p"
			}
		}
		args = append(args, "-vf", vf)
	}
	args = append(args, codecArgs...)

	if config.TwoPass {
		// For 2-pass, this builds pass 2 command
		args = append(args, "-pass", "2")
	}

	args = append(args, config.OutputPath)

	if config.TwoPass {
		log.Printf("Build Software Pass 2 command: ffmpeg %s", strings.Join(args, " "))
	} else {
		log.Printf("Build Software command: ffmpeg %s", strings.Join(args, " "))
	}
	cmd := exec.Command("ffmpeg", args...)
	cmd.Dir = config.WorkDir
	return cmd
}

// BuildPass1Command builds the first pass command for 2-pass encoding.
func (e *SoftwareEncoder) BuildPass1Command(config *EncodeConfig) *exec.Cmd {
	// Use HDR pixel formats for EXR, SDR for PNG
	var pixFmt string
	var colorPrimaries, colorTrc, colorspace string
	if config.SourceFormat == "png" {
		// PNG: SDR format
		pixFmt = "yuv420p"
		if config.UseAlpha {
			pixFmt = "yuva420p"
		}
		colorPrimaries = "bt709"
		colorTrc = "bt709"
		colorspace = "bt709"
	} else {
		// EXR: Use HDR encoding if PreserveHDR is true, otherwise SDR (like PNG)
		if config.PreserveHDR {
			// HDR: Use HLG transfer with bt709 primaries to preserve HDR range while matching PNG color
			pixFmt = "yuv420p10le" // 10-bit to preserve HDR range
			if config.UseAlpha {
				pixFmt = "yuva420p10le"
			}
			colorPrimaries = "bt709"  // bt709 primaries to match PNG color appearance
			colorTrc = "arib-std-b67" // HLG transfer function - preserves HDR range, works on SDR displays
			colorspace = "bt709"      // bt709 colorspace to match PNG
		} else {
			// SDR: Treat as SDR (like PNG) - encode as bt709
			pixFmt = "yuv420p"
			if config.UseAlpha {
				pixFmt = "yuva420p"
			}
			colorPrimaries = "bt709"
			colorTrc = "bt709"
			colorspace = "bt709"
		}
	}

	var codecArgs []string
	switch e.codec {
	case "libaom-av1":
		codecArgs = []string{"-crf", strconv.Itoa(CRFAV1), "-b:v", "0", "-tiles", "2x2", "-g", "240"}
	case "libvpx-vp9":
		// VP9 supports alpha and HDR, use good quality settings
		codecArgs = []string{"-crf", strconv.Itoa(CRFVP9), "-b:v", "0", "-row-mt", "1", "-g", "240"}
	default:
		// H.264: Use High 10 profile for HDR EXR (10-bit), High profile for SDR
		if config.SourceFormat != "png" && config.PreserveHDR {
			codecArgs = []string{"-preset", "veryslow", "-crf", strconv.Itoa(CRFH264), "-profile:v", "high10", "-level", "5.2", "-tune", "film", "-keyint_min", "24", "-g", "240", "-bf", "2", "-refs", "4"}
		} else {
			codecArgs = []string{"-preset", "veryslow", "-crf", strconv.Itoa(CRFH264), "-profile:v", "high", "-level", "5.2", "-tune", "film", "-keyint_min", "24", "-g", "240", "-bf", "2", "-refs", "4"}
		}
	}

	args := []string{
		"-y",
		"-f", "image2",
		"-start_number", fmt.Sprintf("%d", config.StartFrame),
		"-framerate", fmt.Sprintf("%.2f", config.FrameRate),
		"-i", config.InputPattern,
		"-c:v", e.codec,
		"-pix_fmt", pixFmt,
		"-r", fmt.Sprintf("%.2f", config.FrameRate),
		"-color_primaries", colorPrimaries,
		"-color_trc", colorTrc,
		"-colorspace", colorspace,
		"-color_range", "tv",
	}

	// Add video filter for EXR: convert linear RGB based on HDR setting
	// PNG doesn't need any filter as it's already in sRGB
	if config.SourceFormat != "png" {
		var vf string
		if config.PreserveHDR {
			// HDR: Convert linear RGB -> sRGB -> HLG with bt709 primaries
			// This preserves HDR range while matching PNG color appearance
			vf = "format=gbrpf32le,zscale=transferin=8:transfer=13:primariesin=1:primaries=1:matrixin=0:matrix=1:rangein=full:range=full,zscale=transferin=13:transfer=18:primariesin=1:primaries=1:matrixin=1:matrix=1:rangein=full:range=full"
			if config.UseAlpha {
				vf += ",format=yuva420p10le"
			} else {
				vf += ",format=yuv420p10le"
			}
		} else {
			// SDR: Convert linear RGB (EXR) to sRGB (bt709) - simple conversion like Krita does
			// zscale: linear (8) -> sRGB (13) with bt709 primaries/matrix
			vf = "format=gbrpf32le,zscale=transferin=8:transfer=13:primariesin=1:primaries=1:matrixin=0:matrix=1:rangein=full:range=full"
			if config.UseAlpha {
				vf += ",format=yuva420p"
			} else {
				vf += ",format=yuv420p"
			}
		}
		args = append(args, "-vf", vf)
	}

	args = append(args, codecArgs...)
	args = append(args, "-pass", "1", "-f", "null", "/dev/null")

	log.Printf("Build Software Pass 1 command: ffmpeg %s", strings.Join(args, " "))
	cmd := exec.Command("ffmpeg", args...)
	cmd.Dir = config.WorkDir
	return cmd
}