package main

import (
	"errors"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"

	"github.com/spf13/cobra"

	"housecarl/internal/api"
	"housecarl/internal/client"
	"housecarl/internal/model"
)

// Changesets: configuration changes staged to be reviewed and applied
// together. -C/--changeset stages into a changeset as given (housecarld
// still refuses one that isn't open, or another user's unless you are an
// administrator). One from HOUSECARL_CHANGESET is checked first: an
// exported ID outlives its changeset (it gets applied), and IDs keep
// growing, so a stale or mistyped one could name someone else's later. It
// is used only when it is open and yours, and hc says on stderr which
// changeset that is.

var flagChangeset int64

// envChangeset returns the changeset in HOUSECARL_CHANGESET (0 if unset).
func envChangeset() (int64, error) {
	v := os.Getenv("HOUSECARL_CHANGESET")
	if v == "" {
		return 0, nil
	}
	n, err := strconv.ParseInt(v, 10, 64)
	if err != nil || n <= 0 {
		return 0, fmt.Errorf("invalid HOUSECARL_CHANGESET %q", v)
	}
	return n, nil
}

const startHint = "export HOUSECARL_CHANGESET=$(hc changeset create -q)"

// checkEnvChangeset checks the changeset from HOUSECARL_CHANGESET before
// it is used. With mustOwn, it must also be open and the caller's own
// (for staging into it, applying or discarding it).
func checkEnvChangeset(c *client.Client, id int64, mustOwn bool) (*model.Changeset, error) {
	var cs model.Changeset
	if err := c.Do(ctx(), "GET", fmt.Sprintf("/changesets/%d", id), nil, nil, &cs); err != nil {
		var ce *client.Error
		if errors.As(err, &ce) && ce.Status == 404 {
			return nil, fmt.Errorf("HOUSECARL_CHANGESET is %d, but there is no changeset %d: start one with '%s', or 'unset HOUSECARL_CHANGESET' to make changes at once", id, id, startHint)
		}
		return nil, err
	}
	if mustOwn {
		if cs.Status != model.ChangesetOpen {
			return nil, fmt.Errorf("HOUSECARL_CHANGESET is %d, but changeset %d is %s: 'unset HOUSECARL_CHANGESET' to make changes at once, or start a new one with '%s'", id, id, cs.Status, startHint)
		}
		var me api.Whoami
		if err := c.Do(ctx(), "GET", "/auth/whoami", nil, nil, &me); err != nil {
			return nil, err
		}
		mine := me.User != nil && cs.UserID == me.User.ID && (me.User.ID != 0 || cs.Username == me.User.Username)
		if !mine {
			return nil, fmt.Errorf("HOUSECARL_CHANGESET is %d, but changeset %d is %s's (made via %s), not yours, so it isn't used from HOUSECARL_CHANGESET; give it as -C %d to use it anyway, or 'unset HOUSECARL_CHANGESET'", id, id, cs.Username, cs.Via, id)
		}
	}
	if !flagQuiet {
		desc := cs.Description
		if desc == "" {
			desc = "no description"
		}
		fmt.Fprintf(os.Stderr, "changeset %d (%s, %s) from HOUSECARL_CHANGESET\n", id, desc, plural(len(cs.Ops), "operation"))
	}
	return &cs, nil
}

// setupChangeset makes the client stage configuration changes: in
// --changeset's changeset, else HOUSECARL_CHANGESET's (checked before
// the first change).
func setupChangeset(c *client.Client) error {
	if flagChangeset > 0 {
		c.Changeset = flagChangeset
		return nil
	}
	n, err := envChangeset()
	if err != nil || n == 0 {
		return err
	}
	c.Changeset = n
	c.BeforeStage = func() error {
		_, err := checkEnvChangeset(c, n, true)
		return err
	}
	return nil
}

// changesetArg returns the changeset a changeset subcommand works on: the
// ID argument, else --changeset, else HOUSECARL_CHANGESET (checked).
// fromEnv says it came from HOUSECARL_CHANGESET.
func changesetArg(c *client.Client, args []string, mustOwn bool) (id string, fromEnv bool, err error) {
	if len(args) > 0 {
		return args[0], false, nil
	}
	if flagChangeset > 0 {
		return strconv.FormatInt(flagChangeset, 10), false, nil
	}
	n, err := envChangeset()
	if err != nil {
		return "", false, err
	}
	if n == 0 {
		return "", false, errors.New("which changeset? Give its ID, or set HOUSECARL_CHANGESET (" + startHint + ")")
	}
	if _, err := checkEnvChangeset(c, n, mustOwn); err != nil {
		return "", false, err
	}
	return strconv.FormatInt(n, 10), true, nil
}

// envChangesetDone reminds that HOUSECARL_CHANGESET still names a
// changeset that was just applied or discarded.
func envChangesetDone(id, what string) {
	if !flagQuiet {
		fmt.Fprintf(os.Stderr, "HOUSECARL_CHANGESET still names changeset %s, which is now %s: run 'unset HOUSECARL_CHANGESET' (or export a new one) before making more changes\n", id, what)
	}
}

func plural(n int, word string) string {
	if n == 1 {
		return "1 " + word
	}
	return strconv.Itoa(n) + " " + word + "s"
}

// printDiff prints a unified diff, colored on a terminal.
func printDiff(w io.Writer, diff string) {
	color := isTerminal(os.Stdout)
	for _, line := range strings.Split(strings.TrimSuffix(diff, "\n"), "\n") {
		switch {
		case !color:
		case strings.HasPrefix(line, "+++"), strings.HasPrefix(line, "---"):
			line = "\x1b[1m" + line + "\x1b[0m"
		case strings.HasPrefix(line, "+"):
			line = "\x1b[32m" + line + "\x1b[0m"
		case strings.HasPrefix(line, "-"):
			line = "\x1b[31m" + line + "\x1b[0m"
		case strings.HasPrefix(line, "@@"):
			line = "\x1b[36m" + line + "\x1b[0m"
		}
		fmt.Fprintln(w, line)
	}
}

func isTerminal(f *os.File) bool {
	fi, err := f.Stat()
	return err == nil && fi.Mode()&os.ModeCharDevice != 0
}

func changesetCmd() *cobra.Command {
	cmd := &cobra.Command{
		Use:     "changeset",
		Aliases: []string{"changesets", "cs"},
		Short:   "Stage changes to review and apply together",
		Long: `A changeset collects configuration changes to apply together, as one
change in the history. Each change is checked as it is staged; 'hc
changeset diff' shows what applying them would do: the problems, nftables'
check and the ruleset's diff. Over the network an applied changeset is on
probation like any change.

The web UI stages its edits in a changeset by default; hc and the API
make changes at once unless one is named with -C ID or HOUSECARL_CHANGESET.
Changesets staged in the web UI show up here too, and the other way round.`,
		Example: `  export HOUSECARL_CHANGESET=$(hc changeset create "guest network" -q)
  hc zone add guest -i eth1.30
  hc rule add forward --in guest --out wan
  hc changeset diff                 # HOUSECARL_CHANGESET's
  hc changeset apply
  unset HOUSECARL_CHANGESET`,
	}
	cmd.AddCommand(&cobra.Command{
		Use: "create [DESCRIPTION]", Short: "Start a changeset (-q prints only its ID)", Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			in := api.ChangesetInput{}
			if len(args) > 0 {
				in.Description = args[0]
			}
			var cs model.Changeset
			if err := c.Do(ctx(), "POST", "/changesets", nil, in, &cs); err != nil {
				return err
			}
			if flagQuiet || flagOutput == "id" {
				fmt.Println(cs.ID)
				return nil
			}
			fmt.Printf("created changeset %d\nstage changes with -C %d (or export HOUSECARL_CHANGESET=%d), then 'hc changeset apply'\n", cs.ID, cs.ID, cs.ID)
			return nil
		},
	})
	var status string
	var mine bool
	list := &cobra.Command{
		Use: "list", Short: "List changesets (open ones by default)", Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			var css []*model.Changeset
			query := q("status", status)
			if mine {
				query.Set("mine", "1")
			}
			if err := c.Do(ctx(), "GET", "/changesets", query, nil, &css); err != nil {
				return err
			}
			return output(css, func(w io.Writer) {
				fmt.Fprintln(w, "ID\tSTATUS\tBY\tVIA\tOPERATIONS\tUPDATED\tDESCRIPTION")
				for _, cs := range css {
					fmt.Fprintf(w, "%d\t%s\t%s\t%s\t%d\t%s\t%s\n", cs.ID, cs.Status, cs.Username, cs.Via, len(cs.Ops), cs.UpdatedAt.Local().Format("2006-01-02 15:04"), cs.Description)
				}
			})
		},
	}
	list.Flags().StringVar(&status, "status", "open", "open, applied, discarded, or \"\" for all")
	list.Flags().BoolVar(&mine, "mine", false, "only your own")
	cmd.AddCommand(list)
	cmd.AddCommand(&cobra.Command{
		Use: "show [ID]", Short: "Show a changeset's operations (default: -C or HOUSECARL_CHANGESET)", Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			id, _, err := changesetArg(c, args, false)
			if err != nil {
				return err
			}
			var cs model.Changeset
			if err := c.Do(ctx(), "GET", "/changesets/"+id, nil, nil, &cs); err != nil {
				return err
			}
			return output(&cs, func(w io.Writer) {
				fmt.Fprintf(w, "Changeset:\t%d (%s)\n", cs.ID, cs.Status)
				fmt.Fprintf(w, "By:\t%s via %s, %s\n", cs.Username, cs.Via, cs.CreatedAt.Local().Format("2006-01-02 15:04"))
				if cs.Description != "" {
					fmt.Fprintf(w, "Description:\t%s\n", cs.Description)
				}
				if cs.HistoryID != 0 {
					fmt.Fprintf(w, "History:\t%d\n", cs.HistoryID)
				}
				fmt.Fprintln(w, "\nOP\tCHANGE")
				for _, o := range cs.Ops {
					fmt.Fprintf(w, "%d\t%s\n", o.Seq, o.Summary)
				}
			})
		},
	})
	cmd.AddCommand(&cobra.Command{
		Use: "diff [ID]", Short: "Check an open changeset and show what applying it would change (default: -C or HOUSECARL_CHANGESET)", Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			id, _, err := changesetArg(c, args, false)
			if err != nil {
				return err
			}
			var pv api.ChangesetPreview
			if err := c.Do(ctx(), "GET", "/changesets/"+id+"/preview", nil, nil, &pv); err != nil {
				return err
			}
			if flagOutput == "json" || flagOutput == "yaml" {
				return output(&pv, nil)
			}
			for _, ch := range pv.Changes {
				if ch.Kind == model.KindSettings {
					fmt.Printf("would %s settings\n", ch.Action())
				} else {
					fmt.Printf("would %s %s %s\n", ch.Action(), ch.Kind, ch.Label)
				}
			}
			printProblems(os.Stderr, pv.Warnings)
			if pv.Error != nil {
				printProblems(os.Stderr, pv.Error.Problems)
				return fmt.Errorf("changeset %s can't be applied: %s", id, pv.Error.Message)
			}
			if !pv.Valid {
				fmt.Println("nothing to change")
				return nil
			}
			fmt.Println()
			printDiff(os.Stdout, pv.Diff)
			fmt.Printf("\nvalid: nftables accepts the new ruleset; apply with 'hc changeset apply %s'\n", id)
			return nil
		},
	})
	var desc string
	apply := &cobra.Command{
		Use: "apply [ID]", Short: "Apply an open changeset (default: -C or HOUSECARL_CHANGESET)", Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			id, fromEnv, err := changesetArg(c, args, true)
			if err != nil {
				return err
			}
			var resp api.MutationResponse
			if err := c.Do(ctx(), "POST", "/changesets/"+id+"/apply", nil, api.ChangesetInput{Description: desc}, &resp); err != nil {
				return err
			}
			if err := report(&resp); err != nil {
				return err
			}
			if fromEnv {
				envChangesetDone(id, "applied")
			}
			return nil
		},
	}
	apply.Flags().StringVar(&desc, "description", "", "the history entry's description (default: the changeset's)")
	cmd.AddCommand(apply)
	cmd.AddCommand(&cobra.Command{
		Use: "discard [ID]", Short: "Throw away an open changeset (default: -C or HOUSECARL_CHANGESET)", Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			id, fromEnv, err := changesetArg(c, args, true)
			if err != nil {
				return err
			}
			if err := c.Do(ctx(), "POST", "/changesets/"+id+"/discard", nil, nil, nil); err != nil {
				return err
			}
			if !flagQuiet {
				fmt.Printf("discarded changeset %s\n", id)
			}
			if fromEnv {
				envChangesetDone(id, "discarded")
			}
			return nil
		},
	})
	cmd.AddCommand(&cobra.Command{
		Use: "remove [ID] OP", Short: "Remove one operation from an open changeset (default: -C or HOUSECARL_CHANGESET)", Args: cobra.RangeArgs(1, 2),
		RunE: func(cmd *cobra.Command, args []string) error {
			c, err := newClient()
			if err != nil {
				return err
			}
			op := args[len(args)-1]
			id, _, err := changesetArg(c, args[:len(args)-1], true)
			if err != nil {
				return err
			}
			var cs model.Changeset
			if err := c.Do(ctx(), "DELETE", "/changesets/"+id+"/ops/"+op, nil, nil, &cs); err != nil {
				return err
			}
			if !flagQuiet {
				fmt.Printf("removed operation %s; changeset %s has %s\n", op, id, plural(len(cs.Ops), "operation"))
			}
			return nil
		},
	})
	return cmd
}