package skillpack

import (
	"context"
	"fmt"
	"sort"
	"strings"

	mdagent "gitea.stevedudenhoeffer.com/steve/majordomo/agent"
	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
	mdskill "gitea.stevedudenhoeffer.com/steve/majordomo/skill"
)

// Resolve loads the pinned Pack for each enabled subscription from the cache. It
// is how a host turns "this agent subscribes to these packs" into activatable
// packs at run time without touching the network. A pinned digest missing from
// the cache is an error (the host should have cached it at pin/apply time).
// Disabled subscriptions are skipped.
func Resolve(ctx context.Context, cache PackCache, subs []Subscription) ([]*Pack, error) {
	out := make([]*Pack, 0, len(subs))
	for i := range subs {
		s := &subs[i]
		if !s.Enabled {
			continue
		}
		tree, err := cache.Get(ctx, s.PinnedDigest)
		if err != nil {
			return nil, fmt.Errorf("skillpack: resolving %q: %w", s.Name, err)
		}
		pack, err := LoadPack(tree)
		if err != nil {
			return nil, fmt.Errorf("skillpack: loading %q: %w", s.Name, err)
		}
		out = append(out, pack)
	}
	return out, nil
}

// Catalog renders the always-in-prompt block for a set of packs: one line per
// pack (name + description) plus how to load one. This is the whole prompt cost
// of a subscription — the bodies stay out until skill_use is called.
func Catalog(packs []*Pack) string {
	if len(packs) == 0 {
		return ""
	}
	sorted := append([]*Pack(nil), packs...)
	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Manifest.Name < sorted[j].Manifest.Name })

	var b strings.Builder
	b.WriteString("You have access to skills — packaged instructions for specific tasks. ")
	b.WriteString("When a task matches one, call skill_use with its name to load its full instructions before proceeding.\n\n")
	b.WriteString("Available skills:\n")
	for _, p := range sorted {
		fmt.Fprintf(&b, "- %s: %s\n", p.Manifest.Name, p.Manifest.Description)
	}
	return strings.TrimRight(b.String(), "\n")
}

type skillUseArgs struct {
	Name string `json:"name" description:"the exact name of the skill to load, from the Available skills list"`
}

// Activate turns a set of resolved packs into a majordomo agent.Skill: its
// Instructions are the Catalog, and it contributes a single skill_use tool that
// returns a named pack's full body (progressive disclosure). Attach the result
// to an agent with agent.WithSkill. Returns nil when there are no packs, which
// agent.WithSkill tolerates (a nil skill contributes nothing).
//
// stagedDir, if non-empty, is the directory a host has staged the packs' bundled
// files into (see Stage); skill_use appends the concrete path so the model knows
// where to read scripts/references with its file tools. Leave it empty when the
// host has no staging.
func Activate(packs []*Pack, stagedDir string) mdagent.Skill {
	if len(packs) == 0 {
		return nil
	}
	byName := make(map[string]*Pack, len(packs))
	for _, p := range packs {
		byName[p.Manifest.Name] = p
	}

	tool := llm.DefineTool("skill_use",
		"Load the full instructions for a skill by name before doing a task it covers. Returns the skill's instructions and a list of any bundled files.",
		func(_ context.Context, args skillUseArgs) (any, error) {
			p, ok := byName[strings.TrimSpace(args.Name)]
			if !ok {
				return fmt.Sprintf("No skill named %q. Use one of the names from the Available skills list.", args.Name), nil
			}
			return renderPackBody(p, stagedDir), nil
		})

	tb := llm.NewToolbox("skillpack", tool)
	return mdskill.New("skillpacks",
		mdskill.WithInstructions(Catalog(packs)),
		mdskill.WithToolbox(tb),
	)
}

// renderPackBody is what skill_use returns: the pack's instructions plus a
// pointer to its bundled files (with the staged path when known).
func renderPackBody(p *Pack, stagedDir string) string {
	var b strings.Builder
	fmt.Fprintf(&b, "# Skill: %s\n\n%s\n", p.Manifest.Name, p.Manifest.Body)
	if len(p.Bundled) > 0 {
		b.WriteString("\nBundled files")
		if stagedDir != "" {
			fmt.Fprintf(&b, " (under %s)", strings.TrimRight(stagedDir, "/")+"/"+p.Manifest.Name)
		}
		b.WriteString(":\n")
		for _, f := range p.Bundled {
			fmt.Fprintf(&b, "- %s\n", f)
		}
	}
	return strings.TrimRight(b.String(), "\n")
}

// Stage materializes a pack's files under baseDir/<pack name>/ so a host can
// mount them (read-only is the host's concern) into a sandbox the agent's file
// tools can read. Returns the pack's staged directory.
func Stage(p *Pack, baseDir string) (string, error) {
	dir := baseDir + "/" + p.Manifest.Name
	if err := p.Tree.WriteTo(dir); err != nil {
		return "", err
	}
	return dir, nil
}