package cli

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/spf13/cobra"

	"gitea.mynodes.xyz/ilker/llmgw/internal/config"
	"gitea.mynodes.xyz/ilker/llmgw/internal/control/adminapi"
	"gitea.mynodes.xyz/ilker/llmgw/internal/settings"
)

func newConfigCmd(client func() *ctlClient, asJSON *bool) *cobra.Command {
	var version int64
	c := &cobra.Command{
		Use:   "config",
		Short: "The cluster's settings: show, change, and go back",
		Long: "Everything in server.yaml that is not one machine's own — guardrails,\n" +
			"limits, pricing, routing, engines, notifications, the mirror's policy —\n" +
			"is the cluster's, kept in the store and the same on every control plane.\n" +
			"A change is checked, kept as a new version, and in force on every control\n" +
			"plane within seconds: live where it can be (guard), otherwise each control\n" +
			"plane starts again on it, standbys first and the leader last.\n\n" +
			"With no subcommand, prints the settings in force.\n\n" +
			"A machine's own keys (" + strings.Join(config.LocalKeys(), ", ") + ")\n" +
			"stay in its /etc/llmgw/server.yaml; a change there is noticed and applied\n" +
			"on that machine the same way.",
		Example: "  llmgw ctl config\n" +
			"  llmgw ctl config get router.retries\n" +
			"  llmgw ctl config set router.retries 3 --note 'flaky upstream'\n" +
			"  llmgw ctl config set firewall_networks '[10.20.0.0/16]'\n" +
			"  llmgw ctl config edit\n" +
			"  llmgw ctl config history\n" +
			"  llmgw ctl config rollback 4",
		Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, _ []string) error {
			path := "/api/v1/settings"
			if version > 0 {
				path += "?version=" + strconv.FormatInt(version, 10)
			}
			var v adminapi.SettingsView
			if err := client().get(cmd.Context(), path, &v); err != nil {
				return err
			}
			if *asJSON {
				return emitJSON(v)
			}
			fmt.Fprintf(cmd.ErrOrStderr(), "# version %d, %s by %s%s\n", v.Version, v.At.Local().Format(time.DateTime),
				orUnknown(v.By), noteSuffix(v.Note))
			fmt.Fprint(cmd.OutOrStdout(), v.Body)
			return nil
		},
	}
	c.Flags().Int64Var(&version, "version", 0, "an earlier version")
	c.AddCommand(newConfigGetCmd(client), newConfigSetCmd(client), newConfigUnsetCmd(client),
		newConfigEditCmd(client), newConfigHistoryCmd(client, asJSON), newConfigRollbackCmd(client))
	return c
}

func orUnknown(s string) string {
	if s == "" {
		return "unknown"
	}
	return s
}

func noteSuffix(n string) string {
	if n == "" {
		return ""
	}
	return ": " + n
}

// keyPath reads a dotted key, refusing one machine's own.
func keyPath(key string) ([]string, error) {
	path := strings.Split(key, ".")
	if config.IsLocal(path) {
		return nil, fmt.Errorf("%s is each machine's own: change it in that machine's /etc/llmgw/server.yaml, "+
			"where a change is applied by itself too", key)
	}
	return path, nil
}

func newConfigGetCmd(client func() *ctlClient) *cobra.Command {
	return &cobra.Command{
		Use:   "get KEY",
		Short: "One key of the cluster's settings, as YAML",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			path, err := keyPath(args[0])
			if err != nil {
				return err
			}
			var v adminapi.SettingsView
			if err := client().get(cmd.Context(), "/api/v1/settings", &v); err != nil {
				return err
			}
			doc, err := settings.FromBytes("settings", []byte(v.Body))
			if err != nil {
				return err
			}
			n := doc.Node(path)
			if n == nil {
				return fmt.Errorf("%s is not set in the cluster's settings; its default applies (docs/reference.md)", args[0])
			}
			sub, err := settings.FromBytes("value", nil)
			if err != nil {
				return err
			}
			if err := sub.SetNode([]string{"v"}, n); err != nil {
				return err
			}
			b, err := sub.Bytes()
			if err != nil {
				return err
			}
			out := strings.TrimPrefix(string(b), "v:")
			fmt.Fprintln(cmd.OutOrStdout(), strings.TrimSpace(dedent(out)))
			return nil
		},
	}
}

// dedent takes off the two spaces a block nested under one key carries.
func dedent(s string) string {
	lines := strings.Split(s, "\n")
	for i, l := range lines {
		lines[i] = strings.TrimPrefix(l, "  ")
	}
	return strings.Join(lines, "\n")
}

// changeSettings reads the newest settings, changes them, and puts the
// result in force, saying what that does.
func changeSettings(cmd *cobra.Command, client func() *ctlClient, note string,
	change func(doc *settings.Doc) error,
) error {
	ctx := cmd.Context()
	var cur adminapi.SettingsView
	if err := client().get(ctx, "/api/v1/settings", &cur); err != nil {
		return err
	}
	doc, err := settings.FromBytes("settings", []byte(cur.Body))
	if err != nil {
		return err
	}
	if err := change(doc); err != nil {
		return err
	}
	b, err := doc.Bytes()
	if err != nil {
		return err
	}
	return putSettings(cmd, client, cur, b, note)
}

func putSettings(cmd *cobra.Command, client func() *ctlClient, cur adminapi.SettingsView, body []byte, note string) error {
	before, _ := config.Parse([]byte(cur.Body))
	after, err := config.Parse(body)
	if err != nil {
		return err
	}
	changed := config.Changed(before, after)
	if len(changed) == 0 {
		fmt.Fprintln(cmd.OutOrStdout(), "nothing changed")
		return nil
	}
	req, _ := json.Marshal(adminapi.SettingsRequest{Base: cur.Version, Body: string(body), Note: note})
	var v adminapi.SettingsView
	if err := client().put(cmd.Context(), "/api/v1/settings", req, &v); err != nil {
		return err
	}
	fmt.Fprintf(cmd.OutOrStdout(), "version %d: %s\n", v.Version, strings.Join(changed, ", "))
	if onlyLive(changed) {
		fmt.Fprintln(cmd.OutOrStdout(), "in force on every control plane within seconds")
	} else {
		fmt.Fprintln(cmd.OutOrStdout(), "every control plane starts again on it within seconds, standbys first, "+
			"the leader half a minute later; engines keep serving")
	}
	return nil
}

func newConfigSetCmd(client func() *ctlClient) *cobra.Command {
	var note string
	c := &cobra.Command{
		Use:   "set KEY VALUE",
		Short: "Change one key of the cluster's settings; VALUE is YAML",
		Example: "  llmgw ctl config set router.retries 3\n" +
			"  llmgw ctl config set guard.default '[baseline, finance]'\n" +
			"  llmgw ctl config set notify.webhooks '[{url: https://hooks.example/llmgw}]'",
		Args: cobra.ExactArgs(2),
		RunE: func(cmd *cobra.Command, args []string) error {
			path, err := keyPath(args[0])
			if err != nil {
				return err
			}
			return changeSettings(cmd, client, note, func(doc *settings.Doc) error {
				return doc.SetYAML(path, args[1])
			})
		},
	}
	c.Flags().StringVar(&note, "note", "", "why, kept with the version")
	return c
}

func newConfigUnsetCmd(client func() *ctlClient) *cobra.Command {
	var note string
	c := &cobra.Command{
		Use:   "unset KEY",
		Short: "Remove one key from the cluster's settings, so its default applies",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			path, err := keyPath(args[0])
			if err != nil {
				return err
			}
			return changeSettings(cmd, client, note, func(doc *settings.Doc) error {
				if doc.Node(path) == nil {
					return fmt.Errorf("%s is not set", args[0])
				}
				doc.Unset(path)
				return nil
			})
		},
	}
	c.Flags().StringVar(&note, "note", "", "why, kept with the version")
	return c
}

func newConfigEditCmd(client func() *ctlClient) *cobra.Command {
	var note string
	c := &cobra.Command{
		Use:   "edit",
		Short: "Edit the cluster's settings in $EDITOR",
		Long: "Opens the settings in force in $EDITOR (vi when unset). Saved, they are\n" +
			"checked and kept as a new version; a document that does not load is\n" +
			"opened again with the reason, until it does or is left unchanged.",
		Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, _ []string) error {
			var cur adminapi.SettingsView
			if err := client().get(cmd.Context(), "/api/v1/settings", &cur); err != nil {
				return err
			}
			dir, err := os.MkdirTemp("", "llmgw-settings")
			if err != nil {
				return err
			}
			defer os.RemoveAll(dir)
			file := filepath.Join(dir, "settings.yaml")
			body := []byte(cur.Body)
			problem := ""
			for {
				text := body
				if problem != "" {
					text = append([]byte("# NOT SAVED: "+strings.ReplaceAll(problem, "\n", " ")+"\n"), stripProblem(body)...)
				}
				if err := os.WriteFile(file, text, 0o600); err != nil {
					return err
				}
				if err := runEditor(file, cmd.InOrStdin(), cmd.OutOrStdout(), cmd.ErrOrStderr()); err != nil {
					return err
				}
				edited, err := os.ReadFile(file) //nolint:gosec // written above
				if err != nil {
					return err
				}
				edited = stripProblem(edited)
				if bytes.Equal(bytes.TrimSpace(edited), bytes.TrimSpace([]byte(cur.Body))) {
					fmt.Fprintln(cmd.OutOrStdout(), "nothing changed")
					return nil
				}
				err = putSettings(cmd, client, cur, edited, note)
				if err == nil {
					return nil
				}
				if strings.Contains(err.Error(), "changed since they were read") {
					// Somebody else's change came first: opening the editor
					// again on the old base would only be refused again.
					return fmt.Errorf("%w; your edit is not saved", err)
				}
				body, problem = edited, err.Error()
			}
		},
	}
	c.Flags().StringVar(&note, "note", "", "why, kept with the version")
	return c
}

func stripProblem(b []byte) []byte {
	if bytes.HasPrefix(b, []byte("# NOT SAVED: ")) {
		if i := bytes.IndexByte(b, '\n'); i >= 0 {
			return b[i+1:]
		}
	}
	return b
}

func runEditor(file string, in io.Reader, out, errOut io.Writer) error {
	editor := os.Getenv("VISUAL")
	if editor == "" {
		editor = os.Getenv("EDITOR")
	}
	if editor == "" {
		editor = "vi"
	}
	parts := strings.Fields(editor)
	c := exec.Command(parts[0], append(parts[1:], file)...) //nolint:gosec // the operator's own editor
	c.Stdin, c.Stdout, c.Stderr = in, out, errOut
	if err := c.Run(); err != nil {
		return fmt.Errorf("%s: %w", editor, err)
	}
	return nil
}

func newConfigHistoryCmd(client func() *ctlClient, asJSON *bool) *cobra.Command {
	var limit int
	c := &cobra.Command{
		Use:   "history",
		Short: "Versions of the cluster's settings, newest first",
		Args:  cobra.NoArgs,
		RunE: func(cmd *cobra.Command, _ []string) error {
			var list []adminapi.SettingsView
			if err := client().get(cmd.Context(), "/api/v1/settings/history?limit="+strconv.Itoa(limit), &list); err != nil {
				return err
			}
			if *asJSON {
				return emitJSON(list)
			}
			w := tabTo(cmd.OutOrStdout())
			fmt.Fprintln(w, "VERSION\tWHEN\tBY\tNOTE")
			for _, v := range list {
				fmt.Fprintf(w, "%d\t%s\t%s\t%s\n", v.Version, v.At.Local().Format(time.DateTime), orUnknown(v.By), v.Note)
			}
			return w.Flush()
		},
	}
	c.Flags().IntVar(&limit, "limit", 20, "how many")
	return c
}

func newConfigRollbackCmd(client func() *ctlClient) *cobra.Command {
	var note string
	c := &cobra.Command{
		Use:   "rollback VERSION",
		Short: "Put an earlier version of the cluster's settings back in force, as a new version",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			n, err := strconv.ParseInt(args[0], 10, 64)
			if err != nil || n < 1 {
				return errors.New("VERSION is a number from 'llmgw ctl config history'")
			}
			var cur, old adminapi.SettingsView
			if err := client().get(cmd.Context(), "/api/v1/settings", &cur); err != nil {
				return err
			}
			if err := client().get(cmd.Context(), "/api/v1/settings?version="+args[0], &old); err != nil {
				return err
			}
			if note == "" {
				note = "back to version " + args[0]
			}
			return putSettings(cmd, client, cur, []byte(old.Body), note)
		},
	}
	c.Flags().StringVar(&note, "note", "", "why, kept with the version")
	return c
}