package kiosk

import (
	"bytes"
	"fmt"
	"regexp"
	"sort"
	"strings"

	"github.com/goccy/go-yaml"
)

// Manifest is one plugin.yaml. Fields are written in declaration order.
type Manifest struct {
	// Schema is the plugin.yaml format version (SchemaVersion when written).
	Schema int `yaml:"schema"`
	// ID is the plugin ID that plugin.go's ID() returns.
	ID string `yaml:"id"`
	// Module is the go.mod module path: what go get takes.
	Module string `yaml:"module"`
	// Package is the plugin's import path: what summer.yaml lists. It
	// differs from Module for a plugin in a subdirectory of its module.
	Package string `yaml:"package"`
	// Name is the display name: the README's H1 or the name override.
	Name string `yaml:"name"`
	// Description is the README's one-sentence summary or the override.
	Description string `yaml:"description"`
	// Framework is the minimum framework version: the go.mod require of
	// FrameworkModule.
	Framework string `yaml:"framework"`
	// Requires maps each plugin ID that Requires() returns to its minimum
	// version; empty when the plugin ships in the same module or its
	// module is not a go.mod require.
	Requires Requires `yaml:"requires,omitempty"`
	// Overrides holds the --name and --description values; nil when
	// neither is set.
	Overrides *Overrides `yaml:"overrides,omitempty"`
}

// Overrides are the name and description set with summer plugin:manifest
// --name and --description. They survive regeneration until cleared.
type Overrides struct {
	Name        string `yaml:"name,omitempty"`
	Description string `yaml:"description,omitempty"`
}

// Requires maps a required plugin ID to its minimum version. It marshals
// with the IDs sorted, so the generated bytes are stable.
type Requires map[string]string

// MarshalYAML emits the map as a sorted mapping.
func (r Requires) MarshalYAML() (any, error) {
	ids := make([]string, 0, len(r))
	for id := range r {
		ids = append(ids, id)
	}
	sort.Strings(ids)
	out := make(yaml.MapSlice, 0, len(ids))
	for _, id := range ids {
		out = append(out, yaml.MapItem{Key: id, Value: r[id]})
	}
	return out, nil
}

// Marshal returns the plugin.yaml bytes: the Header line, then the fields.
func Marshal(m Manifest) ([]byte, error) {
	if m.Overrides != nil && *m.Overrides == (Overrides{}) {
		m.Overrides = nil
	}
	body, err := yaml.Marshal(m)
	if err != nil {
		return nil, fmt.Errorf("kiosk: marshal %s: %w", FileName, err)
	}
	var b bytes.Buffer
	b.WriteString(Header)
	b.WriteByte('\n')
	b.Write(body)
	return b.Bytes(), nil
}

// Parse reads plugin.yaml bytes. A schema newer than SchemaVersion is an
// error that says to update summer; unknown fields are ignored.
func Parse(data []byte) (Manifest, error) {
	var m Manifest
	if err := yaml.Unmarshal(data, &m); err != nil {
		return Manifest{}, fmt.Errorf("kiosk: parse %s: %w", FileName, err)
	}
	if m.Schema > SchemaVersion {
		return Manifest{}, fmt.Errorf("kiosk: %s has schema %d, this summer reads up to %d; update summer", FileName, m.Schema, SchemaVersion)
	}
	if err := Validate(m); err != nil {
		return Manifest{}, err
	}
	return m, nil
}

var pluginIDRe = regexp.MustCompile(`^[a-z][a-z0-9]*\.[a-z][a-z0-9]*$`)

// Validate checks a manifest: the schema is between 1 and SchemaVersion,
// the ID and every required ID are lowercase vendor.plugin, module and
// package are plain module paths (package inside module), name and
// description are set, and the framework and every non-empty plugin
// minimum is a vX.Y.Z release or a Go pseudo-version.
func Validate(m Manifest) error {
	if m.Schema < 1 || m.Schema > SchemaVersion {
		return fmt.Errorf("kiosk: schema %d is not between 1 and %d", m.Schema, SchemaVersion)
	}
	if !pluginIDRe.MatchString(m.ID) {
		return fmt.Errorf("kiosk: id %q must be lowercase vendor.plugin", m.ID)
	}
	if err := validPath(m.Module); err != nil {
		return fmt.Errorf("kiosk: module: %w", err)
	}
	if err := validPath(m.Package); err != nil {
		return fmt.Errorf("kiosk: package: %w", err)
	}
	if m.Package != m.Module && !strings.HasPrefix(m.Package, m.Module+"/") {
		return fmt.Errorf("kiosk: package %q is not inside module %q", m.Package, m.Module)
	}
	if strings.TrimSpace(m.Name) == "" {
		return fmt.Errorf("kiosk: name is empty")
	}
	if strings.TrimSpace(m.Description) == "" {
		return fmt.Errorf("kiosk: description is empty")
	}
	if !releaseOrPseudo(m.Framework) {
		return fmt.Errorf("kiosk: framework %q must be a vX.Y.Z release", m.Framework)
	}
	for id, v := range m.Requires {
		if !pluginIDRe.MatchString(id) {
			return fmt.Errorf("kiosk: required id %q must be lowercase vendor.plugin", id)
		}
		if v != "" && !releaseOrPseudo(v) {
			return fmt.Errorf("kiosk: minimum %q of %s must be a vX.Y.Z release", v, id)
		}
	}
	return nil
}

func releaseOrPseudo(v string) bool {
	return ValidVersion(v) || isPseudoVersion(v)
}

// validPath accepts a slash-separated module or import path.
func validPath(p string) error {
	switch {
	case p == "":
		return fmt.Errorf("is empty")
	case strings.HasPrefix(p, "-"):
		return fmt.Errorf("%q must not start with -", p)
	case strings.ContainsAny(p, " \t\r\n\\\"'`$;&|*?<>()[]{}@"):
		return fmt.Errorf("%q contains invalid characters", p)
	}
	for _, seg := range strings.Split(p, "/") {
		if seg == "" || seg == "." || seg == ".." {
			return fmt.Errorf("%q has an invalid path segment", p)
		}
	}
	return nil
}