package main

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"text/tabwriter"

	"github.com/spf13/cobra"
)

func addCmd(opts *options) *cobra.Command {
	var name string
	var only []string
	cmd := &cobra.Command{
		Use:   "add <source>",
		Short: "Add the skills in a git repository",
		Long: `Add the skills in a git repository and install them.

<source> is one of:
  owner/repo                 a GitHub repository
  https://host/path.git      any git URL (https, ssh, git or file)
  user@host:path             an SSH remote, as git writes it
  ./path                     a local git repository
optionally followed by #ref to follow a branch or tag, or pin a commit.

Every directory holding a SKILL.md is a skill. Without --skill, all of
them are added, including ones the repository gains later.`,
		Example: `  skills add anthropics/skills
  skills add anthropics/skills --skill pdf --skill xlsx
  skills add git@example.com:me/skills.git#main --name mine`,
		Args: exactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			ws, err := opts.workspace()
			if err != nil {
				return err
			}
			spec, err := parseSpec(args[0])
			if err != nil {
				return usageError{err}
			}
			if name != "" {
				if _, ok := ws.manifest.Sources[name]; ok {
					return fmt.Errorf("a source named %q already exists; pick another --name, or `skills update %s`", name, name)
				}
			}
			src := Source{Source: args[0], Skills: only}
			locked, selected, err := lockSource(cmd.Context(), opts, ws, name, src)
			if err != nil {
				return err
			}
			if name == "" {
				name = defaultSourceName(spec, selected)
				if _, ok := ws.manifest.Sources[name]; ok {
					return fmt.Errorf("a source named %q already exists; choose a name with --name", name)
				}
				if err := ws.checkCollisions(name, selected); err != nil {
					return err
				}
			}
			ws.manifest.Sources[name] = src
			ws.lock.Sources[name] = locked
			if err := ws.save(); err != nil {
				return err
			}
			opts.printf("Added %s at %s: %s\n", name, locked.shortRev(), skillNames(selected))
			return apply(cmd.Context(), opts, ws)
		},
	}
	cmd.Flags().StringVarP(&name, "name", "n", "", "name for the source (default: its only skill, else the repository)")
	cmd.Flags().StringArrayVarP(&only, "skill", "s", nil, "add only this skill; repeat for more")
	return cmd
}

func removeCmd(opts *options) *cobra.Command {
	return &cobra.Command{
		Use:     "remove <source>...",
		Aliases: []string{"rm"},
		Short:   "Remove sources and uninstall their skills",
		Example: `  skills remove pdf`,
		Args:    minArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			ws, err := opts.workspace()
			if err != nil {
				return err
			}
			names, err := ws.sourceNames(args)
			if err != nil {
				return err
			}
			for _, n := range names {
				delete(ws.manifest.Sources, n)
				delete(ws.lock.Sources, n)
				opts.printf("Removed %s\n", n)
			}
			if err := ws.save(); err != nil {
				return err
			}
			return apply(cmd.Context(), opts, ws)
		},
	}
}

func updateCmd(opts *options) *cobra.Command {
	return &cobra.Command{
		Use:   "update [<source>...]",
		Short: "Move sources to the newest commit of their branch or tag",
		Long: `Move sources to the newest commit of the branch or tag they follow, and
install the result. With no arguments, every source is updated.`,
		Example: `  skills update
  skills update pdf`,
		RunE: func(cmd *cobra.Command, args []string) error {
			ws, err := opts.workspace()
			if err != nil {
				return err
			}
			names, err := ws.sourceNames(args)
			if err != nil {
				return err
			}
			changed := false
			for _, n := range names {
				old := ws.lock.Sources[n]
				next, _, err := lockSource(cmd.Context(), opts, ws, n, ws.manifest.Sources[n])
				if err != nil {
					return fmt.Errorf("%s: %w", n, err)
				}
				if next.Rev == old.Rev && fmt.Sprint(next.Skills) == fmt.Sprint(old.Skills) && next.NarHash == old.NarHash {
					opts.printf("%s is up to date at %s\n", n, old.shortRev())
					continue
				}
				changed = true
				ws.lock.Sources[n] = next
				opts.printf("Updated %s from %s to %s%s\n", n, orNone(old.shortRev()), next.shortRev(), diffSkills(old.Skills, next.Skills))
			}
			if changed {
				if err := ws.save(); err != nil {
					return err
				}
			}
			return apply(cmd.Context(), opts, ws)
		},
	}
}

func installCmd(opts *options) *cobra.Command {
	return &cobra.Command{
		Use:   "install",
		Short: "Install exactly the locked skills",
		Long: `Install the skills in the lock file at their locked commits, and uninstall
skills that skills installed but the lock no longer has. Run it after
cloning a manifest onto a new machine. Nothing else in an agent's skills
directory is touched.`,
		Args: exactArgs(0),
		RunE: func(cmd *cobra.Command, args []string) error {
			ws, err := opts.workspace()
			if err != nil {
				return err
			}
			return apply(cmd.Context(), opts, ws)
		},
	}
}

func listCmd(opts *options) *cobra.Command {
	var asJSON bool
	cmd := &cobra.Command{
		Use:     "list",
		Aliases: []string{"ls"},
		Short:   "Show sources, their skills and where they are installed",
		Args:    exactArgs(0),
		RunE: func(cmd *cobra.Command, args []string) error {
			ws, err := opts.workspace()
			if err != nil {
				return err
			}
			return list(ws, asJSON)
		},
	}
	cmd.Flags().BoolVar(&asJSON, "json", false, "print JSON")
	return cmd
}

// lockSource resolves a source to a commit, fetches it and finds its skills.
// name is empty for a source being added.
func lockSource(ctx context.Context, opts *options, ws *workspace, name string, src Source) (LockedSource, []Skill, error) {
	spec, err := parseSpec(src.Source)
	if err != nil {
		return LockedSource{}, nil, err
	}
	opts.progressf("Fetching %s\n", src.Source)
	rev, err := resolve(ctx, spec.URL, spec.Ref)
	if err != nil {
		return LockedSource{}, nil, err
	}
	dir, err := checkout(ctx, spec.URL, rev)
	if err != nil {
		return LockedSource{}, nil, err
	}
	found, err := discover(dir)
	if err != nil {
		return LockedSource{}, nil, err
	}
	if len(found) == 0 {
		return LockedSource{}, nil, fmt.Errorf("found no SKILL.md in %s", src.Source)
	}
	selected, err := selectSkills(found, src.Skills)
	if err != nil {
		return LockedSource{}, nil, err
	}
	if name != "" {
		if err := ws.checkCollisions(name, selected); err != nil {
			return LockedSource{}, nil, err
		}
	}
	locked := LockedSource{URL: spec.URL, Rev: rev, Skills: skillPaths(selected)}
	if managedBy() != "" {
		if locked.NarHash, err = nixFetch(ctx, spec.URL, rev); err != nil {
			return LockedSource{}, nil, err
		}
	}
	return locked, selected, nil
}

// apply makes the installed skills match the lock.
func apply(ctx context.Context, opts *options, ws *workspace) error {
	names, _ := ws.sourceNames(nil)
	if m := managedBy(); m != "" {
		return applyNix(ctx, opts, ws, names, m)
	}
	agents, err := ws.targetAgents()
	if err != nil {
		return err
	}
	dirs := map[string]string{}
	for _, n := range names {
		l, ok := ws.lock.Sources[n]
		if !ok {
			return fmt.Errorf("%s is in the manifest but not the lock; run `skills update %s`", n, n)
		}
		opts.progressf("Fetching %s\n", ws.manifest.Sources[n].Source)
		dir, err := checkout(ctx, l.URL, l.Rev)
		if err != nil {
			return fmt.Errorf("%s: %w", n, err)
		}
		for s, p := range l.Skills {
			dirs[s] = filepath.Join(dir, filepath.FromSlash(p))
		}
	}
	changes, conflicts, err := ws.link(dirs, agents)
	reportChanges(opts, changes)
	if err != nil {
		return err
	}
	if len(conflicts) > 0 {
		return fmt.Errorf("these already exist and were not installed by skills, so they were left alone:\n  %s\nmove them away and run `skills install`",
			strings.Join(conflicts, "\n  "))
	}
	if len(changes) == 0 {
		opts.printf("All skills are installed for %s\n", joinAgents(agents))
	}
	return nil
}

// applyNix fetches every locked source into the Nix store as this user, so
// that the tool named by SKILLS_MANAGED_BY can install them.
func applyNix(ctx context.Context, opts *options, ws *workspace, names []string, manager string) error {
	dirty := false
	for _, n := range names {
		l := ws.lock.Sources[n]
		opts.progressf("Fetching %s into the Nix store\n", ws.manifest.Sources[n].Source)
		hash, err := nixFetch(ctx, l.URL, l.Rev)
		if err != nil {
			return fmt.Errorf("%s: %w", n, err)
		}
		if hash != l.NarHash {
			l.NarHash = hash
			ws.lock.Sources[n] = l
			dirty = true
		}
	}
	if dirty {
		if err := ws.save(); err != nil {
			return err
		}
	}
	opts.printf("Skills are installed by %s: apply your %s configuration to install these changes.\n", manager, manager)
	return nil
}

func reportChanges(opts *options, changes []change) {
	agents := map[string][]string{}
	for _, c := range changes {
		agents[c.Action+"\x00"+c.Skill] = append(agents[c.Action+"\x00"+c.Skill], c.Agent)
	}
	skills := map[string][]string{}
	var order []string
	for k, as := range agents {
		action, skill, _ := strings.Cut(k, "\x00")
		line := capitalize(action) + "\x00" + strings.Join(as, ", ")
		if _, ok := skills[line]; !ok {
			order = append(order, line)
		}
		skills[line] = append(skills[line], skill)
	}
	sort.Strings(order)
	for _, line := range order {
		action, as, _ := strings.Cut(line, "\x00")
		sort.Strings(skills[line])
		opts.printf("%s %s for %s\n", action, strings.Join(skills[line], ", "), as)
	}
}

func list(ws *workspace, asJSON bool) error {
	names, _ := ws.sourceNames(nil)
	agents, agentsErr := ws.targetAgents()
	manager := managedBy()

	type skillOut struct {
		Name   string            `json:"name"`
		Path   string            `json:"path"`
		Status map[string]string `json:"status,omitempty"`
	}
	type sourceOut struct {
		Name   string     `json:"name"`
		Source string     `json:"source"`
		URL    string     `json:"url"`
		Rev    string     `json:"rev"`
		Skills []skillOut `json:"skills"`
	}
	var out []sourceOut
	for _, n := range names {
		l := ws.lock.Sources[n]
		so := sourceOut{Name: n, Source: ws.manifest.Sources[n].Source, URL: l.URL, Rev: l.Rev, Skills: []skillOut{}}
		skills := make([]string, 0, len(l.Skills))
		for s := range l.Skills {
			skills = append(skills, s)
		}
		sort.Strings(skills)
		for _, s := range skills {
			sk := skillOut{Name: s, Path: l.Skills[s]}
			if manager == "" && agentsErr == nil {
				sk.Status = map[string]string{}
				want := filepath.Join(dataDir(), "checkouts", repoKey(l.URL), l.Rev, filepath.FromSlash(l.Skills[s]))
				for _, a := range agents {
					sk.Status[a.Name] = linkState(filepath.Join(a.skillsDir(), s), want).String()
				}
			}
			so.Skills = append(so.Skills, sk)
		}
		out = append(out, so)
	}

	if asJSON {
		enc := json.NewEncoder(os.Stdout)
		enc.SetIndent("", "  ")
		if out == nil {
			out = []sourceOut{}
		}
		return enc.Encode(out)
	}
	if len(out) == 0 {
		fmt.Printf("No skills in %s yet. Add some with `skills add owner/repo`.\n", ws.manifestPath)
		return nil
	}
	tw := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	for _, so := range out {
		fmt.Fprintf(tw, "%s\t%s\t%s\n", so.Name, orNone(shortRev(so.Rev)), so.Source)
		for _, sk := range so.Skills {
			fmt.Fprintf(tw, "  %s\t%s\t%s\n", sk.Name, summarizeStatus(sk.Status, manager), sk.Path)
		}
	}
	if err := tw.Flush(); err != nil {
		return err
	}
	if agentsErr != nil && manager == "" {
		fmt.Fprintln(os.Stderr, "skills:", agentsErr)
	}
	return nil
}

func summarizeStatus(status map[string]string, manager string) string {
	if manager != "" {
		return "via " + manager
	}
	byState := map[string][]string{}
	for a, s := range status {
		byState[s] = append(byState[s], a)
	}
	if len(byState) == 1 {
		for s := range byState {
			return s
		}
	}
	var parts []string
	for s, as := range byState {
		sort.Strings(as)
		parts = append(parts, s+" for "+strings.Join(as, ", "))
	}
	sort.Strings(parts)
	return strings.Join(parts, "; ")
}

func diffSkills(old, next map[string]string) string {
	var added, removed []string
	for n := range next {
		if _, ok := old[n]; !ok {
			added = append(added, n)
		}
	}
	for n := range old {
		if _, ok := next[n]; !ok {
			removed = append(removed, n)
		}
	}
	sort.Strings(added)
	sort.Strings(removed)
	var parts []string
	if len(added) > 0 {
		parts = append(parts, "new: "+strings.Join(added, ", "))
	}
	if len(removed) > 0 {
		parts = append(parts, "gone: "+strings.Join(removed, ", "))
	}
	if len(parts) == 0 {
		return ""
	}
	return " (" + strings.Join(parts, "; ") + ")"
}

func joinAgents(agents []agent) string {
	names := make([]string, len(agents))
	for i, a := range agents {
		names[i] = a.Name
	}
	return strings.Join(names, ", ")
}

func shortRev(rev string) string {
	if len(rev) > 7 {
		return rev[:7]
	}
	return rev
}

func orNone(s string) string {
	if s == "" {
		return "(none)"
	}
	return s
}

func capitalize(s string) string {
	if s == "" {
		return s
	}
	return strings.ToUpper(s[:1]) + s[1:]
}