package main

import (
	"errors"
	"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
}

// forceFetch replaces a definition that is already stored. It is the only way to
// do so, because a file in the user directory may be one the user has edited and
// nothing on disk says which it is.
var forceFetch bool

// NewKeyboardFetchCmd is `keyboard fetch`. It belongs to the keyboard command
// because what it fetches belongs to a board: the file is looked up by the
// board's vendor and product ID, so there is nothing to fetch without one.
func NewKeyboardFetchCmd() *cobra.Command {
	cmd := &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.\n\n" +
			"A definition that is already stored for this keyboard is not replaced, because\n" +
			"it may be one you have edited. Edit that file, or pass --force to overwrite it.",
		Args: cobra.NoArgs,
		RunE: runKeyboardFetch,
	}
	cmd.Flags().BoolVar(&forceFetch, "force", false,
		"Replace a definition that is already stored, discarding whatever that file holds")
	return cmd
}

// NewKeyboardDefinitionsCmd is `keyboard definitions`, and the name is the noun
// rather than a verb on purpose. `keyboard list` reads as listing the
// keyboards, which is what `keyboard info` does, and the root already has a
// `list` that means the profile store; one verb must not mean two stores.
func NewKeyboardDefinitionsCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "definitions",
		Short: "List the definition files in the data directory, and those built in",
		Args:  cobra.NoArgs,
		RunE:  runKeyboardDefinitions,
	}
}

func runKeyboardFetch(cmd *cobra.Command, args []string) error {
	// A definition is a property of a board, not of a lighting channel, so this
	// asks for the board alone and names no zone.
	target, err := prepareTarget("")
	if err != nil {
		return err
	}

	dir, err := ensureDefinitionsDir()
	if err != nil {
		return err
	}

	// The check comes before the download, so a user whose definition is already
	// there is told so without waiting on the network and without the answer
	// depending on VIA still carrying the board. It matches by content rather
	// than by file name, because what identifies a definition is the vendor and
	// product ID inside it and the name of the file is only a label.
	stored := storedDefinitionsFor(dir, target.Device.VendorID, target.Device.ProductID)
	if len(stored) > 0 && !forceFetch {
		return fmt.Errorf("a definition for %s (0x%04X/0x%04X) is already at %s; it may hold your "+
			"edits, so fetch does not replace it, use --force to overwrite it or edit that file",
			stored[0].Name, target.Device.VendorID, target.Device.ProductID, describeDataDir(stored[0].Path))
	}

	def, err := fetchDefinition(target.Device.VendorID, target.Device.ProductID)
	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)
	}

	// A definition that was replaced under a different file name is removed
	// rather than left standing beside the new one: two files describing one
	// board leave which of them is read to the order the directory happens to
	// come back in. The removal follows the write, so a write that failed keeps
	// what was there.
	for _, old := range stored {
		if old.Path == path {
			continue
		}
		if err := os.Remove(old.Path); err != nil {
			return fmt.Errorf("remove replaced %s: %w", old.Path, err)
		}
	}

	verb := "Saved"
	if len(stored) > 0 {
		verb = "Replaced"
	}
	fmt.Fprintf(cmd.OutOrStdout(), "%s definition for %s (0x%04X/0x%04X) to %s\n",
		verb, 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
}

// storedDefinitionsFor returns the definitions the user directory already holds
// for a board. It is a slice because two files can describe one board: the
// vendor issues the same vendor and product ID to two models, which
// definitions/README.md records, and only one of the two files is read.
//
// A directory that cannot be read is not an answer. A file in it may be
// unreadable, and "nothing stored" is what a fetch acts on, so an unreadable
// directory leaves the fetch to write rather than refuse.
func storedDefinitionsFor(dir string, vendorID, productID uint16) []*intrgb.Definition {
	defs, err := intrgb.LoadDefinitionsDir(dir)
	if err != nil {
		return nil
	}
	var out []*intrgb.Definition
	for _, def := range defs {
		if def.Matches(vendorID, productID) {
			out = append(out, def)
		}
	}
	return out
}

func runKeyboardDefinitions(cmd *cobra.Command, args []string) error {
	dir := definitionsPath()
	// Both sources are listed, not just the directory: the file built into the
	// binary is where the names for a board that cannot be fetched come from, and
	// a listing that did not show it would say the tool has no definition for a
	// board it has one for.
	userDefs, dirErr := intrgb.LoadDefinitionsDir(dir)
	switch {
	case dirErr == nil, errors.Is(dirErr, os.ErrNotExist):
		// A directory that is not there yet is not an error: a user who has never
		// fetched one has none. A file inside it that cannot be read is, because
		// a definition the user placed and that does not work is worth saying.
	default:
		return dirErr
	}
	builtIn := builtInDefinitions()

	lines := make([]definitionLine, 0, len(userDefs)+len(builtIn))
	for _, def := range userDefs {
		lines = append(lines, definitionLineFor(def, "user"))
	}
	for _, def := range builtIn {
		lines = append(lines, definitionLineFor(def, "built-in"))
	}

	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 and none built into this binary\n", describeDataDir(dir))
		return nil
	}
	fmt.Fprintf(cmd.OutOrStdout(), "Definitions\n\n  user  %s\n  built into this binary\n", describeDataDir(dir))
	for _, line := range lines {
		shadowed := ""
		if line.Source == "user" && isShadowed(line, builtIn) {
			shadowed = "  (shadows the built-in copy)"
		}
		fmt.Fprintf(cmd.OutOrStdout(), "\n%s (%s/%s)  %s  %s%s\n",
			line.Name, line.VendorID, line.ProductID, line.Source, line.Path, shadowed)
		for _, ch := range line.Channels {
			fmt.Fprintf(cmd.OutOrStdout(), "  %-10s %-10s %d effects\n", ch.Name, ch.Subsystem, ch.Effects)
		}
	}
	return nil
}

// definitionLineFor is one definition file in the shape the list command reports.
// The source is carried on the line because the path alone does not say where it
// is: a file built into the binary has a path relative to the build, not one a
// user can open.
func definitionLineFor(def *intrgb.Definition, source string) definitionLine {
	line := definitionLine{
		Name:      def.Name,
		VendorID:  fmt.Sprintf("0x%04X", def.VendorID),
		ProductID: fmt.Sprintf("0x%04X", def.ProductID),
		Path:      def.Path,
		Source:    source,
	}
	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),
		})
	}
	return line
}

// isShadowed reports whether the built-in set holds a definition for the same
// board, which the file in the user directory overrides. Saying so is the point:
// the two files disagree, and only one of them is read.
func isShadowed(line definitionLine, builtIn []*intrgb.Definition) bool {
	for _, def := range builtIn {
		if fmt.Sprintf("0x%04X", def.VendorID) == line.VendorID &&
			fmt.Sprintf("0x%04X", def.ProductID) == line.ProductID {
			return true
		}
	}
	return false
}

// 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. Source is "user" for a file in the user directory
// and "built-in" for one compiled into the binary, and it is what says which
// file is read when both describe the same board.
type definitionLine struct {
	Name      string              `json:"name"`
	VendorID  string              `json:"vendorId"`
	ProductID string              `json:"productId"`
	Path      string              `json:"path"`
	Source    string              `json:"source"`
	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)
}