package vendor

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/m3tam3re/agent-lib/internal/discovery"
	"github.com/m3tam3re/agent-lib/internal/lockfile"
)

// ValidationError names one broken rule.
type ValidationError struct {
	Source  string `json:"source,omitempty"`
	Rule    string `json:"rule"`
	Message string `json:"message"`
}

// Validation is the full offline verdict over a lockfile and its external area.
type Validation struct {
	Valid  bool              `json:"valid"`
	Errors []ValidationError `json:"errors"`
}

// Validate checks the hard selection rules and the lockfile/external-area
// consistency, entirely offline.
func Validate(workDir string, lf *lockfile.Lockfile) Validation {
	v := Validation{Valid: true}
	for _, name := range sortedSourceNames(lf) {
		src := lf.Sources[name]
		v.checkSelection(name, src)
		v.checkExternalArea(workDir, name, src)
	}
	sort.Slice(v.Errors, func(i, j int) bool {
		if v.Errors[i].Source != v.Errors[j].Source {
			return v.Errors[i].Source < v.Errors[j].Source
		}
		return v.Errors[i].Rule < v.Errors[j].Rule
	})
	v.Valid = len(v.Errors) == 0
	return v
}

func (v *Validation) fail(source, rule, format string, args ...any) {
	v.Errors = append(v.Errors, ValidationError{
		Source:  source,
		Rule:    rule,
		Message: fmt.Sprintf(format, args...),
	})
}

func (v *Validation) checkSelection(name string, src *lockfile.Source) {
	switch src.Selection.Mode {
	case lockfile.ModeAll:
		if len(src.Selection.Include) > 0 {
			v.fail(name, "selection", "source %q: include list is set but mode is all (remove the include list or switch to include mode)", name)
		}
	case lockfile.ModeInclude:
		if len(src.Selection.Exclude) > 0 {
			v.fail(name, "selection", "source %q: exclude list is only valid in all mode", name)
		}
		inventory := map[string]bool{}
		for _, items := range src.Inventory {
			for _, id := range items {
				inventory[id] = true
			}
		}
		for _, inc := range src.Selection.Include {
			if !inventory[inc] {
				v.fail(name, "selection", "source %q: include entry %q is not in the pinned inventory", name, inc)
			}
		}
	default:
		v.fail(name, "selection", "source %q: unknown selection mode %q (want %q or %q)", name, src.Selection.Mode, lockfile.ModeAll, lockfile.ModeInclude)
	}
}

func (v *Validation) checkExternalArea(workDir, name string, src *lockfile.Source) {
	base := filepath.Join(workDir, externalDir, name)
	if _, err := os.Stat(base); err != nil {
		v.fail(name, "tree", "source %q: external area %s is missing", name, base)
		return
	}
	for _, typ := range lockfile.Types {
		want := map[string]bool{}
		for _, upstreamID := range src.Inventory[typ] {
			want[deployedName(upstreamID, src.Renames)] = true
		}
		got, err := scanDeployedNames(filepath.Join(base, typ), typ)
		if err != nil {
			v.fail(name, "tree", "source %q: reading %s area: %v", name, typ, err)
			continue
		}
		for _, dep := range sortedSet(want) {
			if !got[dep] {
				v.fail(name, "tree", "source %q: %s item %q is pinned in the lockfile but missing from the external area", name, typ, dep)
			}
		}
		for _, dep := range sortedSet(got) {
			if !want[dep] {
				v.fail(name, "tree", "source %q: %s item %q exists in the external area but is not in the lockfile", name, typ, dep)
			}
		}
	}
}

func scanDeployedNames(dir, typ string) (map[string]bool, error) {
	out := map[string]bool{}
	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return out, nil
		}
		return nil, err
	}
	for _, e := range entries {
		switch typ {
		case lockfile.TypeSkill:
			if e.IsDir() {
				out[e.Name()] = true
			}
		case lockfile.TypeCommand, lockfile.TypeAgent:
			if strings.HasSuffix(e.Name(), ".md") {
				out[strings.TrimSuffix(e.Name(), ".md")] = true
			}
		case lockfile.TypeMcp:
			name := e.Name()
			if strings.HasSuffix(name, ".yaml") {
				out[strings.TrimSuffix(name, ".yaml")] = true
			} else if strings.HasSuffix(name, ".yml") {
				out[strings.TrimSuffix(name, ".yml")] = true
			}
		}
	}
	return out, nil
}

func sortedSourceNames(lf *lockfile.Lockfile) []string {
	out := make([]string, 0, len(lf.Sources))
	for name := range lf.Sources {
		out = append(out, name)
	}
	sort.Strings(out)
	return out
}

func sortedSet(m map[string]bool) []string {
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}

// ItemInfo describes one deployed item for inspect.
type ItemInfo struct {
	UpstreamID  string   `json:"upstream_id"`
	DeployedID  string   `json:"deployed_id"`
	Name        string   `json:"name,omitempty"`
	Description string   `json:"description,omitempty"`
	Tags        []string `json:"tags,omitempty"`
	Warnings    []string `json:"warnings,omitempty"`
}

// SourceSummary is one row of vendor list.
type SourceSummary struct {
	Name   string         `json:"name"`
	URL    string         `json:"url"`
	Ref    string         `json:"ref"`
	Rev    string         `json:"rev"`
	Mode   string         `json:"mode"`
	Counts map[string]int `json:"counts"`
	Total  int            `json:"total"`
}

// List summarizes every source from the lockfile.
func List(lf *lockfile.Lockfile) []SourceSummary {
	var out []SourceSummary
	for _, name := range sortedSourceNames(lf) {
		src := lf.Sources[name]
		s := SourceSummary{Name: name, URL: src.URL, Ref: src.Ref, Rev: src.Rev, Mode: string(src.Selection.Mode), Counts: map[string]int{}}
		for _, typ := range lockfile.Types {
			n := len(src.Inventory[typ])
			if n > 0 {
				s.Counts[typ] = n
				s.Total += n
			}
		}
		out = append(out, s)
	}
	return out
}

// InspectReport is the full per-source view with metadata from the external area.
type InspectReport struct {
	Name     string                `json:"name"`
	URL      string                `json:"url"`
	Ref      string                `json:"ref"`
	Rev      string                `json:"rev"`
	Mode     string                `json:"mode"`
	Items    map[string][]ItemInfo `json:"items"`
	Warnings []string              `json:"warnings,omitempty"`
}

// Inspect reads the external area of one source and enriches the pinned
// inventory with frontmatter metadata from the deployed files.
func Inspect(workDir, name string, lf *lockfile.Lockfile) (*InspectReport, error) {
	src, ok := lf.Sources[name]
	if !ok {
		return nil, fmt.Errorf("source %q is not in the lockfile", name)
	}
	base := filepath.Join(workDir, externalDir, name)
	tree := &discovery.FsTree{Root: base}
	warningsByPrefix := map[string][]string{}
	for _, w := range src.Warnings {
		prefix, rest, found := strings.Cut(w, ": ")
		if found {
			warningsByPrefix[prefix] = append(warningsByPrefix[prefix], rest)
		}
	}
	report := &InspectReport{
		Name:     name,
		URL:      src.URL,
		Ref:      src.Ref,
		Rev:      src.Rev,
		Mode:     string(src.Selection.Mode),
		Items:    map[string][]ItemInfo{},
		Warnings: src.Warnings,
	}
	for _, typ := range lockfile.Types {
		for _, upstreamID := range src.Inventory[typ] {
			dep := deployedName(upstreamID, src.Renames)
			info := ItemInfo{UpstreamID: upstreamID, DeployedID: dep, Warnings: warningsByPrefix[typ+"/"+upstreamID]}
			switch typ {
			case lockfile.TypeSkill:
				if data, err := tree.ReadFile(typ + "/" + dep + "/SKILL.md"); err == nil {
					fillFrontmatter(&info, data)
				}
			case lockfile.TypeMcp:
			default:
				if data, err := tree.ReadFile(typ + "/" + dep + ".md"); err == nil {
					fillFrontmatter(&info, data)
				}
			}
			report.Items[typ] = append(report.Items[typ], info)
		}
	}
	return report, nil
}

func fillFrontmatter(info *ItemInfo, data []byte) {
	fm, _ := discovery.ParseFrontmatter(data)
	info.Name = fm.Name
	info.Description = fm.Description
	info.Tags = fm.Tags
}