package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/spf13/cobra"
	intrgb "netdome.biz/paul/qmk-rgb/internal/rgb"
	"netdome.biz/paul/qmk-rgb/internal/via"
)

// definitionHost serves the definitions VIA ships, one file per board, named by
// vendor and product ID. The path segment is the definition generation, not the
// protocol version: a board gets v3 and falls back to v2.
const definitionHost = "https://www.usevia.app"

// httpGet is a seam so a fetch can be tested without a network. It returns the
// body and the status code.
var httpGet = func(url string) ([]byte, int, error) {
	resp, err := http.Get(url)
	if err != nil {
		return nil, 0, err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	return body, resp.StatusCode, err
}

func NewDefinitionCmd() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "definition",
		Short: "Manage keyboard definition files",
		Long: "A keyboard's effect names come from a VIA definition file, the same one VIA\n" +
			"itself uses. `fetch` downloads the file for the connected keyboard into the\n" +
			"data directory; to use a file you already have, put it in that directory or\n" +
			"pass it with --definition.",
	}
	cmd.AddCommand(newDefinitionFetchCmd(), newDefinitionListCmd())
	return cmd
}

func newDefinitionFetchCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "fetch",
		Short: "Download the definition file for the connected keyboard",
		Long: "Identify the connected keyboard, then download its VIA definition into the\n" +
			"data directory. VIA does not carry a definition for every board, and answers\n" +
			"an unknown one with its own web page, so a downloaded file is parsed and\n" +
			"matched against the keyboard before it is stored.",
		Args: cobra.NoArgs,
		RunE: runDefinitionFetch,
	}
}

func newDefinitionListCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "list",
		Short: "List the definition files in the data directory",
		Args:  cobra.NoArgs,
		RunE:  runDefinitionList,
	}
}

func runDefinitionFetch(cmd *cobra.Command, args []string) error {
	target, err := prepareTarget()
	if err != nil {
		return err
	}

	def, err := fetchDefinition(target.Device.VendorID, target.Device.ProductID)
	if err != nil {
		return err
	}

	dir, err := ensureDefinitionsDir()
	if err != nil {
		return err
	}
	path := filepath.Join(dir, definitionFileName(def))
	if err := os.WriteFile(path, []byte(def.raw), 0o644); err != nil {
		return fmt.Errorf("write %s: %w", path, err)
	}

	fmt.Fprintf(cmd.OutOrStdout(), "Saved definition for %s (0x%04X/0x%04X) to %s\n",
		def.Definition.Name, def.Definition.VendorID, def.Definition.ProductID, describeDataDir(path))
	for _, ch := range def.channels {
		fmt.Fprintf(cmd.OutOrStdout(), "  %-10s %d effects\n", ch.Subsystem(), len(def.Definition.Catalog.Effects(ch)))
	}
	return nil
}

func runDefinitionList(cmd *cobra.Command, args []string) error {
	dir := definitionsPath()
	if _, statErr := os.Stat(dir); os.IsNotExist(statErr) {
		if jsonOutput {
			return encodeJSON(cmd.OutOrStdout(), struct {
				Directory   string           `json:"directory"`
				Definitions []definitionLine `json:"definitions"`
			}{Directory: dir, Definitions: []definitionLine{}})
		}
		fmt.Fprintf(cmd.OutOrStdout(), "No definition directory yet at %s; run `definition fetch` "+
			"or put a manufacturer file there\n", dir)
		return nil
	}
	defs, err := intrgb.LoadDefinitionsDir(dir)
	if err != nil {
		return err
	}

	lines := make([]definitionLine, 0, len(defs))
	for _, def := range defs {
		line := definitionLine{
			Name:      def.Name,
			VendorID:  fmt.Sprintf("0x%04X", def.VendorID),
			ProductID: fmt.Sprintf("0x%04X", def.ProductID),
			Path:      def.Path,
		}
		for _, ch := range via.LightingChannels {
			effects := def.Catalog.Effects(ch)
			if len(effects) == 0 {
				continue
			}
			// The label is what VIA calls the channel, so the name here is the
			// name the user sees there. The subsystem stays as the fallback and
			// as the spelling that works everywhere.
			name := def.Labels[uint16(ch)]
			if name == "" {
				name = ch.Subsystem()
			}
			line.Channels = append(line.Channels, definitionChannel{
				Name:      name,
				Subsystem: ch.Subsystem(),
				Channel:   uint8(ch),
				Effects:   len(effects),
			})
		}
		lines = append(lines, line)
	}

	if jsonOutput {
		return encodeJSON(cmd.OutOrStdout(), struct {
			Directory   string           `json:"directory"`
			Definitions []definitionLine `json:"definitions"`
		}{Directory: dir, Definitions: lines})
	}

	if len(lines) == 0 {
		fmt.Fprintf(cmd.OutOrStdout(), "No definition files in %s\n", dir)
		return nil
	}
	fmt.Fprintf(cmd.OutOrStdout(), "Definitions in %s\n\n", describeDataDir(dir))
	for _, line := range lines {
		fmt.Fprintf(cmd.OutOrStdout(), "%s (%s/%s) %s\n", line.Name, line.VendorID, line.ProductID, line.Path)
		for _, ch := range line.Channels {
			fmt.Fprintf(cmd.OutOrStdout(), "  %-10s %-10s %d effects\n", ch.Name, ch.Subsystem, ch.Effects)
		}
	}
	return nil
}

// definitionLine is one definition file as the list command reports it. The
// identifiers are hex strings, the way the files themselves spell them, so the
// two can be compared by eye.
type definitionLine struct {
	Name      string              `json:"name"`
	VendorID  string              `json:"vendorId"`
	ProductID string              `json:"productId"`
	Path      string              `json:"path"`
	Channels  []definitionChannel `json:"channels"`
}

// definitionChannel is one lighting channel a definition names effects for.
type definitionChannel struct {
	Name      string `json:"name"`
	Subsystem string `json:"subsystem"`
	Channel   uint8  `json:"channel"`
	Effects   int    `json:"effects"`
}

// fetchedDefinition is a definition together with the bytes it came from, so it
// can be stored exactly as it was served.
type fetchedDefinition struct {
	Definition *intrgb.Definition
	raw        string
	channels   []via.Channel
}

// fetchDefinition downloads the definition for a board. It is separate from the
// command so the download and the checks can be tested on their own.
func fetchDefinition(vendorID, productID uint16) (*fetchedDefinition, error) {
	vpid := intrgb.VendorProductID(vendorID, productID)

	var lastReason string
	for _, version := range []string{"v3", "v2"} {
		url := fmt.Sprintf("%s/definitions/%s/%d.json", definitionHost, version, vpid)
		body, status, err := httpGet(url)
		if err != nil {
			lastReason = err.Error()
			continue
		}
		if status != http.StatusOK {
			lastReason = fmt.Sprintf("HTTP %d", status)
			continue
		}

		def, err := intrgb.ParseDefinition(url, body)
		if err != nil {
			lastReason = "the server did not return a definition"
			continue
		}
		if !def.Matches(vendorID, productID) {
			lastReason = fmt.Sprintf("it is a definition for 0x%04X/0x%04X", def.VendorID, def.ProductID)
			continue
		}
		return &fetchedDefinition{
			Definition: def,
			raw:        string(body),
			channels:   via.LightingChannels,
		}, nil
	}

	return nil, fmt.Errorf("no definition for this keyboard (0x%04X/0x%04X) at %s: %s; "+
		"if the manufacturer publishes one, put it in %s or pass --definition",
		vendorID, productID, definitionHost, lastReason, ensureDefinitionsDirHint())
}

// ensureDefinitionsDirHint is the directory a message can name, with the user
// directory named outright so the advice to put a file somewhere is actionable.
// A directory that cannot be created is not this message's problem, so the
// lookup is not created here.
func ensureDefinitionsDirHint() string {
	return describeDataDir(definitionsPath())
}

// definitionFileName names a stored definition after the board, so a directory
// of them is readable.
func definitionFileName(def *fetchedDefinition) string {
	name := def.Definition.Name
	var b strings.Builder
	for _, r := range strings.ToLower(name) {
		switch {
		case r >= 'a' && r <= 'z', r >= '0' && r <= '9':
			b.WriteRune(r)
		default:
			b.WriteRune('_')
		}
	}
	slug := strings.Trim(b.String(), "_")
	if slug == "" {
		slug = "keyboard"
	}
	return fmt.Sprintf("%s_0x%04X_0x%04X.json", slug, def.Definition.VendorID, def.Definition.ProductID)
}