package commandkit

import (
	"strings"

	internalcobra "gitea.maximumdirect.net/eric/CommandKit/internal/cobra"
	commandmeta "gitea.maximumdirect.net/eric/CommandKit/internal/commandmeta"
	"gitea.maximumdirect.net/eric/CommandKit/internal/commandpath"
)

type completionContext struct {
	route           routeResult
	command         *commandmeta.Command
	aliases         []commandmeta.FlagAlias
	completed       []string
	tail            []string
	current         string
	commandPosition bool
}

func resolveCompletionContext(snapshot *routingSnapshot, completed []string, current string) completionContext {
	context := completionContext{completed: append([]string(nil), completed...), current: current}
	if snapshot == nil {
		return context
	}
	context.route = resolveEnteredRoute(completed, snapshot)
	switch context.route.kind {
	case routeCanonical:
		context.command = completionCommand(snapshot.metadata, context.route.canonicalPath)
		if context.command == nil || len(context.route.args) < len(context.route.canonicalPath) {
			context.command = nil
			return context
		}
		context.tail = append([]string(nil), context.route.args[len(context.route.canonicalPath):]...)
		context.aliases = snapshot.flagAliases[context.route.canonicalPath.Key()].neutralRecords()
		context.commandPosition = len(context.tail) == 0
	case routeDiscovery:
		context.command = &commandmeta.Command{CoreFlags: commandmeta.ReportingFlags()}
		context.tail = append([]string(nil), context.route.args...)
		context.aliases = snapshot.discoveryFlags[context.route.discoveryPath.Key()].neutralRecords()
	}
	return context
}

func completionCommand(root *commandmeta.Command, path commandpath.Path) *commandmeta.Command {
	current := root
	for _, name := range path {
		if current == nil {
			return nil
		}
		var next *commandmeta.Command
		for _, child := range current.Children {
			if child.Name == name {
				next = child
				break
			}
		}
		current = next
	}
	return current
}

func completionChildren(snapshot *routingSnapshot, context completionContext) []commandmeta.CompletionChoice {
	if snapshot == nil || context.command == nil || !context.commandPosition {
		return nil
	}
	var choices []commandmeta.CompletionChoice
	for _, child := range context.command.Children {
		if !strings.HasPrefix(child.Name, context.current) || (len(context.route.canonicalPath) == 0 && child.Name == internalcobra.CompletionQueryToken) {
			continue
		}
		entered := append(append([]string(nil), context.completed...), child.Name)
		route := resolveEnteredRoute(entered, snapshot)
		intended := append(context.route.canonicalPath.Clone(), child.Name)
		if route.kind == routeCanonical && route.canonicalPath.Equal(intended) {
			choices = append(choices, commandmeta.CompletionChoice{Value: child.Name, Description: child.Summary})
		}
	}
	return choices
}