package main

import (
	"fmt"
	"os"
	"path/filepath"

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

// definitionFlag names a definition file to use instead of looking one up.
var definitionFlag string

// resolveCatalog returns the effect catalog for a board, in the order the tool
// trusts: the file named by --definition, then the definition in the data
// directory that matches the board. The second return value says which of the two
// it was, because a board that has no names at all is a different situation from
// one whose names came from somewhere the user can see.
//
// This is the one place a catalog is looked up. A command that reached for a
// catalog itself would silently ignore a definition file the user had placed,
// which is the whole point of having one.
func resolveCatalog(target targetDeviceData) (*intrgb.Catalog, string, error) {
	if definitionFlag != "" {
		def, err := intrgb.LoadDefinition(definitionFlag)
		if err != nil {
			return nil, "", err
		}
		if !def.Matches(target.Device.VendorID, target.Device.ProductID) {
			return nil, "", fmt.Errorf("%s is a definition for %s (0x%04X/0x%04X), not for this keyboard (0x%04X/0x%04X)",
				definitionFlag, def.Name, def.VendorID, def.ProductID,
				target.Device.VendorID, target.Device.ProductID)
		}
		return def.Catalog, def.Path, nil
	}

	catalog, source, err := resolveCatalogFor(target.Device.VendorID, target.Device.ProductID)
	return catalog, source, err
}

// resolveCatalogFor is the lookup without a target, for the commands that report
// on a board rather than open it.
func resolveCatalogFor(vendorID, productID uint16) (*intrgb.Catalog, string, error) {
	if definitionFlag != "" {
		def, err := intrgb.LoadDefinition(definitionFlag)
		if err != nil {
			return nil, "", err
		}
		if !def.Matches(vendorID, productID) {
			return nil, "", nil
		}
		return def.Catalog, def.Path, nil
	}

	if dir, err := definitionsDir(); err == nil {
		if defs, loadErr := intrgb.LoadDefinitionsDir(dir); loadErr == nil {
			if def := intrgb.FindDefinition(defs, vendorID, productID); def != nil {
				return def.Catalog, def.Path, nil
			}
		}
	}

	// No definition for this board, and nothing is compiled in: the keyboard holds
	// numbers, not names, and a board with no names is driven through raw IDs.
	return nil, "", nil
}

// lookupPaths returns the directories a data file is looked for in: the one
// holding the executable, then the working directory, which is the order the
// profile directory uses too.
func lookupPaths() []string {
	var paths []string
	if exe, err := os.Executable(); err == nil {
		paths = append(paths, filepath.Dir(exe))
	}
	if cwd, err := os.Getwd(); err == nil {
		paths = append(paths, cwd)
	}
	return paths
}

// definitionLabels returns the channel names a definition gives the board, which
// are the names VIA shows. They are the only channel names there are: a board
// without a definition is addressed by its QMK subsystem name.
func definitionLabels(vendorID, productID uint16) map[uint16]string {
	def := loadedDefinition(vendorID, productID)
	if def == nil {
		return nil
	}
	return def.Labels
}

// loadedDefinition returns the definition file for a board, from the data
// directory or from the file --definition names, and nil when there is none.
func loadedDefinition(vendorID, productID uint16) *intrgb.Definition {
	if definitionFlag != "" {
		if def, err := intrgb.LoadDefinition(definitionFlag); err == nil && def.Matches(vendorID, productID) {
			return def
		}
		return nil
	}
	dir, err := definitionsDir()
	if err != nil {
		return nil
	}
	defs, err := intrgb.LoadDefinitionsDir(dir)
	if err != nil {
		return nil
	}
	return intrgb.FindDefinition(defs, vendorID, productID)
}

// applyDefinitionLabels returns the display names a board answers to and, beside
// them, the alternatives each channel keeps. The definition's label is the name
// the board is called in VIA; the QMK subsystem name stays an accepted
// alternative, because it follows from the channel number and is the one a
// document can promise without knowing the board.
// Only a channel the definition names gets a display name, and that is
// deliberate. Adding an entry for every QMK lighting channel would put
// "backlight" on channel 1 of a board that has none, where the same word is also
// the board's name for channel 3 — and a name that reaches two channels is
// refused. A channel the definition does not name is addressed by its subsystem
// name, which is what the channel number alone tells us.
func applyDefinitionLabels(vendorID, productID uint16) (map[uint16]string, map[uint16][]string) {
	labels := definitionLabels(vendorID, productID)
	display := make(map[uint16]string, len(labels))
	alternatives := make(map[uint16][]string, len(labels))
	for number, label := range labels {
		display[number] = label
		if subsystem := via.Channel(number).Subsystem(); subsystem != label {
			alternatives[number] = []string{subsystem}
		}
	}
	return display, alternatives
}

// boardName is what a board is called: the name its definition gives it, else the
// USB product string the keyboard itself reports, else an honest placeholder.
func boardName(dev intdevice.Device, _ map[uint16]string) string {
	if def := loadedDefinition(dev.VendorID, dev.ProductID); def != nil && def.Name != "" {
		return def.Name
	}
	if dev.Name != "" {
		return dev.Name
	}
	return "unknown model"
}

// definitionsDir returns the data directory, looked for next to the executable
// first and then in the working directory.
var definitionsDir = func() (string, error) {
	paths := lookupPaths()
	for _, p := range paths {
		dir := filepath.Join(p, intrgb.DefinitionsDir)
		if info, err := os.Stat(dir); err == nil && info.IsDir() {
			return dir, nil
		}
	}
	if len(paths) == 0 {
		return intrgb.DefinitionsDir, nil
	}
	return filepath.Join(paths[0], intrgb.DefinitionsDir), nil
}

// ensureDefinitionsDir returns the data directory, creating it if it is not
// there yet, so a fetch has somewhere to write to.
func ensureDefinitionsDir() (string, error) {
	dir, err := definitionsDir()
	if err != nil {
		return "", err
	}
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", fmt.Errorf("create %s: %w", dir, err)
	}
	return dir, nil
}