package main

import (
	"fmt"
	"strconv"
	"strings"

	intdevice "netdome.biz/paul/qmk-rgb/internal/device"
	intrgb "netdome.biz/paul/qmk-rgb/internal/rgb"
	"netdome.biz/paul/qmk-rgb/internal/via"
)

type zoneProtocol interface {
	SetValue(via.Channel, uint8, uint8) error
	SetColor(via.Channel, uint8, uint8) error
}

type rgbProtocol interface {
	zoneProtocol
	GetValue(via.Channel, uint8) ([]byte, error)
	DetectChannels() ([]via.Channel, error)
	Close() error
}

// targetDeviceData is everything a command needs before it opens the keyboard.
type targetDeviceData struct {
	Device  intdevice.Device
	Display map[uint16]string
	// Alternatives are the names a channel also answers to besides the one its
	// definition gives it, so a name the user already knows keeps working.
	Alternatives map[uint16][]string
	// Requested is nil when no --zone was given, which means every channel
	// the keyboard has.
	Requested []via.Channel
}

// prepareTarget resolves the keyboard, its display names and the requested
// channels. Enumeration does not open a HID handle, so an unusable --zone value
// is still rejected before the device is opened.
var prepareTarget = func() (targetDeviceData, error) {
	devices, err := discoverAll()
	if err != nil {
		return targetDeviceData{}, fmt.Errorf("discover: %w", err)
	}

	dev, err := selectDevice(devices, targetDevice)
	if err != nil {
		return targetDeviceData{}, err
	}

	// A channel is named by the definition file that describes the board, because
	// those are the names VIA shows. Without a definition the QMK subsystem name
	// follows from the channel number and is all there is.
	display, alternatives := applyDefinitionLabels(dev.VendorID, dev.ProductID)

	requested, err := resolveZoneName(targetZone, display, alternatives)
	if err != nil {
		return targetDeviceData{}, err
	}

	dev.Name = boardName(dev, display)

	return targetDeviceData{
		Device:       dev,
		Display:      display,
		Alternatives: alternatives,
		Requested:    requested,
	}, nil
}

func forEachChannel(channels []via.Channel, fn func(via.Channel) error) error {
	for _, ch := range channels {
		if err := fn(ch); err != nil {
			return err
		}
	}
	return nil
}

func setValueOnChannels(proto zoneProtocol, channels []via.Channel, param, value uint8) error {
	return forEachChannel(channels, func(ch via.Channel) error {
		return proto.SetValue(ch, param, value)
	})
}

// zoneResult records what was requested for a zone and what the keyboard
// reported afterwards. The two differ on real hardware: the Impact 80 clamps
// brightness at 160 on the logo and side channels and scales it up to 255 on
// the backlight channel.
type zoneResult struct {
	Name      string
	Requested uint8
	Applied   uint8
}

// Mismatch reports whether the keyboard applied something other than the
// requested value.
func (r zoneResult) Mismatch() bool { return r.Applied != r.Requested }

// anyMismatch reports whether any zone deviated from the request.
func anyMismatch(results []zoneResult) bool {
	for _, r := range results {
		if r.Mismatch() {
			return true
		}
	}
	return false
}

// formatResults renders one line stating what each selected zone actually
// holds, so a partial application is visible instead of being summarised as
// the value that was asked for.
func formatResults(label string, results []zoneResult) string {
	var b strings.Builder
	b.WriteString(label)
	for _, r := range results {
		fmt.Fprintf(&b, " %s %d", r.Name, r.Applied)
	}
	if len(results) > 0 {
		fmt.Fprintf(&b, " (requested %d)", results[0].Requested)
	}
	return b.String()
}

// readBackValues reads one value ID from every channel, in the order given.
// Every verified set reads back through this, so a parameter that needs no new
// read-back path reuses it.
func readBackValues(proto rgbProtocol, channels []via.Channel, display map[uint16]string, param uint8) ([]uint8, error) {
	values := make([]uint8, 0, len(channels))
	for _, ch := range channels {
		raw, err := proto.GetValue(ch, param)
		if err != nil {
			return nil, fmt.Errorf("read back value 0x%02x for %s: %w", param, channelName(ch, display), err)
		}
		if len(raw) == 0 {
			return nil, fmt.Errorf("read back value 0x%02x for %s: empty response", param, channelName(ch, display))
		}
		values = append(values, raw[0])
	}
	return values, nil
}

// setValueVerified writes one value ID to every zone and reads each back, so a
// clamped or rescaled value is reported instead of silently claimed as set.
// The firmware transform differs per channel and per value ID, so the read-back
// is not optional for any parameter the keyboard rescales.
func setValueVerified(proto rgbProtocol, channels []via.Channel, display map[uint16]string, param, value uint8) ([]zoneResult, error) {
	if err := setValueOnChannels(proto, channels, param, value); err != nil {
		return nil, err
	}

	applied, err := readBackValues(proto, channels, display, param)
	if err != nil {
		return nil, err
	}

	results := make([]zoneResult, 0, len(channels))
	for i, ch := range channels {
		results = append(results, zoneResult{Name: channelName(ch, display), Requested: value, Applied: applied[i]})
	}
	return results, nil
}

// effectResult records the effect a zone was asked for and the one the keyboard
// holds afterwards. The Impact 80's logo and side channels do not take effect ID
// 0: the firmware reads it as "lighting off" and leaves the mode register where
// it was, so the effect that is still running has to be named rather than
// reported as the requested one.
type effectResult struct {
	Name          string
	RequestedName string
	RequestedID   uint8
	AppliedName   string
	AppliedID     uint8
}

// Mismatch reports whether the keyboard holds an effect other than the one
// requested.
func (r effectResult) Mismatch() bool { return r.AppliedID != r.RequestedID }

// anyEffectMismatch reports whether any zone kept an effect of its own.
func anyEffectMismatch(results []effectResult) bool {
	for _, r := range results {
		if r.Mismatch() {
			return true
		}
	}
	return false
}

// formatEffectResults names the effect each selected zone actually holds, so an
// effect the keyboard refused is visible instead of being summarised as the one
// that was asked for.
func formatEffectResults(requestedName string, results []effectResult) string {
	var b strings.Builder
	b.WriteString("Effect")
	for _, r := range results {
		fmt.Fprintf(&b, " %s %q (%d)", r.Name, r.AppliedName, r.AppliedID)
	}
	if len(results) > 0 {
		fmt.Fprintf(&b, " (requested %q (%d))", requestedName, results[0].RequestedID)
	}
	return b.String()
}

// setEffectVerified writes one effect ID per channel and reads every channel
// back. It cannot reuse setValueVerified, because one effect name is a
// different index on each subsystem, so the requested value is carried per
// target while the read-back stays shared.
func setEffectVerified(proto rgbProtocol, targets []intrgb.EffectTarget, display map[uint16]string, catalog *intrgb.Catalog) ([]effectResult, error) {
	channels := make([]via.Channel, 0, len(targets))
	requested := make(map[via.Channel]uint8, len(targets))
	for _, t := range targets {
		if err := proto.SetValue(t.Channel, uint8(intrgb.EffectID), t.ID); err != nil {
			return nil, fmt.Errorf("set effect on %s: %w", channelName(t.Channel, display), err)
		}
		channels = append(channels, t.Channel)
		requested[t.Channel] = t.ID
	}

	applied, err := readBackValues(proto, channels, display, uint8(intrgb.EffectID))
	if err != nil {
		return nil, err
	}

	results := make([]effectResult, 0, len(channels))
	for i, ch := range channels {
		results = append(results, effectResult{
			Name:          channelName(ch, display),
			RequestedName: catalog.EffectName(ch, requested[ch]),
			RequestedID:   requested[ch],
			AppliedName:   catalog.EffectName(ch, applied[i]),
			AppliedID:     applied[i],
		})
	}
	return results, nil
}

// setBrightnessVerified writes the brightness and reads every channel back.
func setBrightnessVerified(proto rgbProtocol, channels []via.Channel, display map[uint16]string, value uint8) ([]zoneResult, error) {
	return setValueVerified(proto, channels, display, uint8(intrgb.Brightness), value)
}

// setSpeedVerified writes the speed and reads every channel back.
func setSpeedVerified(proto rgbProtocol, channels []via.Channel, display map[uint16]string, value uint8) ([]zoneResult, error) {
	return setValueVerified(proto, channels, display, uint8(intrgb.Speed), value)
}

// formatEffectIDResults renders the same line as formatEffectResults, with the
// numbers: the request was a number, and a board without a definition has no name
// to put in its place.
func formatEffectIDResults(results []effectResult) string {
	var b strings.Builder
	b.WriteString("Effect")
	for _, r := range results {
		fmt.Fprintf(&b, " %s %d", r.Name, r.AppliedID)
	}
	if len(results) > 0 {
		fmt.Fprintf(&b, " (requested %d)", results[0].RequestedID)
	}
	return b.String()
}

// colorResult records the hue and saturation one channel holds after a color was
// written to it. The color value ID carries two bytes, so both components are
// read back: a keyboard that stored another saturation must not be reported as
// having taken the requested color.
type colorResult struct {
	Name                string
	RequestedHue        uint8
	RequestedSaturation uint8
	Hue                 uint8
	Saturation          uint8
}

// Mismatch reports whether the keyboard stored something other than the
// requested color.
func (r colorResult) Mismatch() bool {
	return r.Hue != r.RequestedHue || r.Saturation != r.RequestedSaturation
}

// setColorVerified writes one hue and saturation to every channel and reads each
// back, for the same reason setValueVerified exists: the command must report
// what the keyboard holds, not what it was asked for.
func setColorVerified(proto rgbProtocol, channels []via.Channel, display map[uint16]string, hue, saturation uint8) ([]colorResult, error) {
	if err := setColorOnChannels(proto, channels, hue, saturation); err != nil {
		return nil, err
	}

	results := make([]colorResult, 0, len(channels))
	for _, ch := range channels {
		raw, err := proto.GetValue(ch, uint8(intrgb.ColorValue))
		if err != nil {
			return nil, fmt.Errorf("read back color for %s: %w", channelName(ch, display), err)
		}
		if len(raw) < 2 {
			return nil, fmt.Errorf("read back color for %s: got %d bytes, want hue and saturation", channelName(ch, display), len(raw))
		}
		results = append(results, colorResult{
			Name:                channelName(ch, display),
			RequestedHue:        hue,
			RequestedSaturation: saturation,
			Hue:                 raw[0],
			Saturation:          raw[1],
		})
	}
	return results, nil
}

func setColorOnChannels(proto zoneProtocol, channels []via.Channel, hue, saturation uint8) error {
	return forEachChannel(channels, func(ch via.Channel) error {
		return proto.SetColor(ch, hue, saturation)
	})
}

func setBrightnessOnChannels(proto zoneProtocol, channels []via.Channel, value uint8) error {
	return setValueOnChannels(proto, channels, uint8(intrgb.Brightness), value)
}

func setSpeedChannels(proto zoneProtocol, channels []via.Channel, value uint8) error {
	return setValueOnChannels(proto, channels, uint8(intrgb.Speed), value)
}

func disableLightingOnChannels(proto zoneProtocol, channels []via.Channel) error {
	return forEachChannel(channels, func(ch via.Channel) error {
		if err := proto.SetValue(ch, uint8(intrgb.EffectID), 0); err != nil {
			return err
		}
		return proto.SetValue(ch, uint8(intrgb.Brightness), 0)
	})
}

func enableLightingOnChannels(proto zoneProtocol, channels []via.Channel, catalog *intrgb.Catalog) error {
	return forEachChannel(channels, func(ch via.Channel) error {
		effect, ok := catalog.DefaultEffect(ch)
		if !ok {
			return fmt.Errorf("no default effect for %s", channelName(ch, nil))
		}
		if err := proto.SetValue(ch, uint8(intrgb.EffectID), effect); err != nil {
			return err
		}
		return proto.SetValue(ch, uint8(intrgb.Brightness), 160)
	})
}

// openTarget opens the keyboard and resolves the requested channels against the
// ones it actually has. It is a seam because a command needs all three: the
// handle it writes to, the names it reports with, and the channels it may touch.
var openTarget = func() (rgbProtocol, targetDeviceData, []via.Channel, error) {
	target, err := prepareTarget()
	if err != nil {
		return nil, targetDeviceData{}, nil, err
	}

	proto, err := via.New(target.Device)
	if err != nil {
		return nil, targetDeviceData{}, nil, fmt.Errorf("open protocol: %w", err)
	}

	channels, err := resolveChannels(proto, target)
	if err != nil {
		proto.Close()
		return nil, targetDeviceData{}, nil, err
	}
	return proto, target, channels, nil
}

// resolveChannels intersects the requested channels with the detected ones, and
// refuses a name that resolves to a channel this keyboard does not have.
func resolveChannels(proto rgbProtocol, target targetDeviceData) ([]via.Channel, error) {
	present, err := proto.DetectChannels()
	if err != nil {
		return nil, err
	}

	if err := displayNameConflicts(target.Display, present); err != nil {
		return nil, err
	}

	if target.Requested == nil {
		if len(present) == 0 {
			return nil, fmt.Errorf("this keyboard exposes no VIA lighting channels")
		}
		return present, nil
	}

	presentSet := make(map[via.Channel]bool, len(present))
	for _, ch := range present {
		presentSet[ch] = true
	}

	var found []via.Channel
	for _, ch := range target.Requested {
		if presentSet[ch] {
			found = append(found, ch)
		}
	}
	if len(found) == 0 {
		return nil, fmt.Errorf("channel %s is not present on this keyboard", target.Requested[0].Subsystem())
	}
	return found, nil
}

// lightingEnabled reports whether a channel is lit: a mode other than none and a
// brightness above zero.
func lightingEnabled(mode, brightness uint8) bool {
	return mode != 0 && brightness > 0
}
func ParseUint8(s string) (uint8, error) {
	v, err := strconv.ParseUint(s, 10, 8)
	if err != nil {
		return 0, fmt.Errorf("invalid value: %w", err)
	}
	return uint8(v), nil
}