package flaggy

// Help represents the values needed to render a Help page
type Help struct {
	Subcommands    []HelpSubcommand
	Positionals    []HelpPositional
	Flags          []HelpFlag
	UsageString    string
	CommandName    string
	PrependMessage string
	AppendMessage  string
	Message        string
	Description    string
}

// HelpSubcommand is used to template subcommand Help output
type HelpSubcommand struct {
	ShortName   string
	LongName    string
	Description string
	Position    int
}

// HelpPositional is used to template positional Help output
type HelpPositional struct {
	Name         string
	Description  string
	Required     bool
	Position     int
	DefaultValue string
}

// HelpFlag is used to template string flag Help output
type HelpFlag struct {
	ShortName    string
	LongName     string
	Description  string
	DefaultValue string
}

// ExtractValues extracts Help template values from a subcommand and its parent
// parser.  The parser is required in order to detect default flag settings
// for help and version outut.
func (h *Help) ExtractValues(p *Parser, message string) {

	// accept message string for output
	h.Message = message

	// extract Help values from the current subcommand in context
	// prependMessage string
	h.PrependMessage = p.subcommandContext.AdditionalHelpPrepend
	// appendMessage  string
	h.AppendMessage = p.subcommandContext.AdditionalHelpAppend
	// command name
	h.CommandName = p.subcommandContext.Name
	// description
	h.Description = p.subcommandContext.Description

	// subcommands    []HelpSubcommand
	for _, cmd := range p.subcommandContext.Subcommands {
		if cmd.Hidden {
			continue
		}
		newHelpSubcommand := HelpSubcommand{
			ShortName:   cmd.ShortName,
			LongName:    cmd.Name,
			Description: cmd.Description,
			Position:    cmd.Position,
		}
		h.Subcommands = append(h.Subcommands, newHelpSubcommand)
	}

	// parse positional flags into help output structs
	for _, pos := range p.subcommandContext.PositionalFlags {
		if pos.Hidden {
			continue
		}
		newHelpPositional := HelpPositional{
			Name:         pos.Name,
			Position:     pos.Position,
			Description:  pos.Description,
			Required:     pos.Required,
			DefaultValue: pos.defaultValue,
		}
		h.Positionals = append(h.Positionals, newHelpPositional)
	}

	// if the built-in version flag is enabled, then add it as a help flag
	if p.ShowVersionWithVersionFlag {
		defaultVersionFlag := HelpFlag{
			ShortName:    "",
			LongName:     versionFlagLongName,
			Description:  "Displays the program version string.",
			DefaultValue: "",
		}
		h.Flags = append(h.Flags, defaultVersionFlag)
	}

	// if the built-in help flag exists, then add it as a help flag
	if p.ShowHelpWithHFlag {
		defaultHelpFlag := HelpFlag{
			ShortName:    helpFlagShortName,
			LongName:     helpFlagLongName,
			Description:  "Displays help with available flag, subcommand, and positional value parameters.",
			DefaultValue: "",
		}
		h.Flags = append(h.Flags, defaultHelpFlag)
	}

	// go through every flag in the subcommand and add it to help output
	h.parseFlagsToHelpFlags(p.subcommandContext.Flags)

	// go through every flag in the parent parser and add it to help output
	h.parseFlagsToHelpFlags(p.Flags)

	// formulate the usage string
	// first, we capture all the command and positional names by position
	commandsByPosition := make(map[int]string)
	for _, pos := range p.subcommandContext.PositionalFlags {
		if pos.Hidden {
			continue
		}
		if len(commandsByPosition[pos.Position]) > 0 {
			commandsByPosition[pos.Position] = commandsByPosition[pos.Position] + "|" + pos.Name
		} else {
			commandsByPosition[pos.Position] = pos.Name
		}
	}
	for _, cmd := range p.subcommandContext.Subcommands {
		if cmd.Hidden {
			continue
		}
		if len(commandsByPosition[cmd.Position]) > 0 {
			commandsByPosition[cmd.Position] = commandsByPosition[cmd.Position] + "|" + cmd.Name
		} else {
			commandsByPosition[cmd.Position] = cmd.Name
		}
	}

	// find the highest position count in the map
	var highestPosition int
	for i := range commandsByPosition {
		if i > highestPosition {
			highestPosition = i
		}
	}

	// only have a usage string if there are positional items
	var usageString string
	if highestPosition > 0 {
		// find each positional value and make our final string
		usageString = p.subcommandContext.Name
		for i := 1; i <= highestPosition; i++ {
			if len(commandsByPosition[i]) > 0 {
				usageString = usageString + " [" + commandsByPosition[i] + "]"
			} else {
				// dont keep listing after the first position without any properties
				// it will be impossible to reach anything beyond here anyway
				break
			}
		}
	}

	h.UsageString = usageString

}

// parseFlagsToHelpFlags parses the specified slice of flags into
// help flags on the the calling help command
func (h *Help) parseFlagsToHelpFlags(flags []*Flag) {
	for _, f := range flags {
		if f.Hidden {
			continue
		}

		// parse help values out if the flag hasn't been parsed yet
		if !f.parsed {
			f.parsed = true
			// parse the default value as a string and remember it for help output
			f.defaultValue, _ = f.returnAssignmentVarValueAsString()
		}

		// determine the default value based on the assignment variable
		defaultValue := f.defaultValue

		// dont show nils
		if defaultValue == "<nil>" {
			defaultValue = ""
		}

		// for bools, dont show a default of false
		_, isBool := f.AssignmentVar.(*bool)
		if isBool {
			b := f.AssignmentVar.(*bool)
			if *b == false {
				defaultValue = ""
			}
		}

		newHelpFlag := HelpFlag{
			ShortName:    f.ShortName,
			LongName:     f.LongName,
			Description:  f.Description,
			DefaultValue: defaultValue,
		}
		h.AddFlagToHelp(newHelpFlag)
	}
}

// AddFlagToHelp adds a flag to help output if it does not exist
func (h *Help) AddFlagToHelp(f HelpFlag) {
	for _, existingFlag := range h.Flags {
		if len(existingFlag.ShortName) > 0 && existingFlag.ShortName == f.ShortName {
			return
		}
		if len(existingFlag.LongName) > 0 && existingFlag.LongName == f.LongName {
			return
		}
	}
	h.Flags = append(h.Flags, f)
}