// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package openapi3gen

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

	"gitea.dev/modules/json"

	"github.com/getkin/kin-openapi/openapi2"
	"github.com/getkin/kin-openapi/openapi2conv"
	"github.com/getkin/kin-openapi/openapi3"
)

// rxDeprecated matches "deprecated" as a word at the start of a description
// or preceded by whitespace/punctuation that indicates a leading marker (e.g.
// "Deprecated: true", "deprecated (use X instead)"). Rejects negated phrases
// like "not deprecated" or "previously deprecated, now supported".
var rxDeprecated = regexp.MustCompile(`(?i)(?:^|[\n.;])\s*deprecated\b`)

// Convert parses a Swagger 2.0 spec and returns an OAS3 spec, applying
// Gitea-specific post-processing: file-schema fixups, URI formats,
// deprecated flags, and shared-enum extraction.
//
// astEnumMap is a value-set-key → Go-type-name(s) map (built by
// ScanSwaggerEnumTypes). When a value set is shared by multiple Go types,
// per-property disambiguation uses the x-go-enum-desc extension. If a shared
// enum in the spec has no matching entry, Convert returns an error — no
// fallback naming.
func Convert(swaggerJSON []byte, astEnumMap map[string][]string) (*openapi3.T, error) {
	var swagger2 openapi2.T
	if err := json.Unmarshal(swaggerJSON, &swagger2); err != nil {
		return nil, fmt.Errorf("parsing swagger 2.0: %w", err)
	}

	oas3, err := openapi2conv.ToV3(&swagger2)
	if err != nil {
		return nil, fmt.Errorf("converting to openapi 3.0: %w", err)
	}

	fixFileSchemas(oas3)
	addURIFormats(oas3)
	addDeprecatedFlags(oas3)
	if err := extractSharedEnums(oas3, astEnumMap); err != nil {
		return nil, err
	}
	return oas3, nil
}

func fixFileSchemas(doc *openapi3.T) {
	for _, pathItem := range doc.Paths.Map() {
		for _, op := range []*openapi3.Operation{
			pathItem.Get, pathItem.Post, pathItem.Put, pathItem.Patch,
			pathItem.Delete, pathItem.Head, pathItem.Options, pathItem.Trace,
		} {
			if op == nil {
				continue
			}
			for _, resp := range op.Responses.Map() {
				if resp.Value == nil {
					continue
				}
				for _, mediaType := range resp.Value.Content {
					fixSchema(mediaType.Schema)
				}
			}
			if op.RequestBody != nil && op.RequestBody.Value != nil {
				for _, mediaType := range op.RequestBody.Value.Content {
					fixSchema(mediaType.Schema)
				}
			}
		}
	}
}

// fixSchema rewrites any "type: file" schemas to the OAS3 equivalent
// (type: string, format: binary), recursing into Properties, Items, and
// AllOf/OneOf/AnyOf/Not branches. $ref nodes are skipped so shared schemas
// are rewritten exactly once when visited through their declaration.
func fixSchema(ref *openapi3.SchemaRef) {
	if ref == nil || ref.Value == nil || ref.Ref != "" {
		return
	}
	s := ref.Value
	if s.Type.Is("file") {
		s.Type = &openapi3.Types{"string"}
		s.Format = "binary"
	}
	for _, p := range s.Properties {
		fixSchema(p)
	}
	fixSchema(s.Items)
	for _, sub := range s.AllOf {
		fixSchema(sub)
	}
	for _, sub := range s.OneOf {
		fixSchema(sub)
	}
	for _, sub := range s.AnyOf {
		fixSchema(sub)
	}
	fixSchema(s.Not)
}

// addURIFormats sets format: uri on string properties whose names indicate
// they hold URLs. This information is lost in Swagger 2.0 but is valuable
// for code generators.
func addURIFormats(doc *openapi3.T) {
	if doc.Components == nil {
		return
	}
	for _, schemaRef := range doc.Components.Schemas {
		if schemaRef.Value == nil {
			continue
		}
		for propName, propRef := range schemaRef.Value.Properties {
			if propRef == nil || propRef.Value == nil || propRef.Ref != "" {
				continue
			}
			prop := propRef.Value
			if !prop.Type.Is("string") || prop.Format != "" {
				continue
			}
			if isURLProperty(propName) {
				prop.Format = "uri"
			}
		}
	}
}

func isURLProperty(name string) bool {
	if strings.HasSuffix(name, "_url") {
		return true
	}
	switch name {
	case "url", "html_url", "clone_url":
		return true
	}
	return false
}

// addDeprecatedFlags sets deprecated: true on schema properties whose
// description starts with a "deprecated" marker (e.g. "Deprecated: true"
// or "deprecated (use X instead)"). Does not match negated phrases.
func addDeprecatedFlags(doc *openapi3.T) {
	if doc.Components == nil {
		return
	}
	for _, schemaRef := range doc.Components.Schemas {
		if schemaRef.Value == nil {
			continue
		}
		for _, propRef := range schemaRef.Value.Properties {
			if propRef == nil || propRef.Value == nil || propRef.Ref != "" {
				continue
			}
			if rxDeprecated.MatchString(propRef.Value.Description) {
				propRef.Value.Deprecated = true
			}
		}
	}
}

type enumUsage struct {
	schemaName string
	propName   string
	propRef    *openapi3.SchemaRef
	inItems    bool
}

// extractSharedEnums finds identical enum arrays used by multiple schema
// properties, creates a standalone named schema for each, and replaces
// the inline enums with $ref pointers.
//
// If the derived enum name collides with an existing component schema, or
// no // swagger:enum annotation matches the value set, generation aborts
// with an actionable error — there are no silent fallbacks.
func extractSharedEnums(doc *openapi3.T, astEnumMap map[string][]string) error {
	if doc.Components == nil {
		return nil
	}

	type groupKey struct {
		valueSet string
		typeName string
	}
	enumGroups := map[groupKey][]enumUsage{}
	groupOrder := []groupKey{} // deterministic iteration

	addUsage := func(key groupKey, u enumUsage) {
		if _, seen := enumGroups[key]; !seen {
			groupOrder = append(groupOrder, key)
		}
		enumGroups[key] = append(enumGroups[key], u)
	}

	for schemaName, schemaRef := range doc.Components.Schemas {
		if schemaRef.Value == nil {
			continue
		}
		for propName, propRef := range schemaRef.Value.Properties {
			if propRef == nil || propRef.Value == nil || propRef.Ref != "" {
				continue
			}
			if len(propRef.Value.Enum) > 1 && propRef.Value.Type.Is("string") {
				key := groupKey{
					valueSet: EnumKey(propRef.Value.Enum),
					typeName: extractEnumTypeName(propRef.Value, astEnumMap),
				}
				addUsage(key, enumUsage{schemaName, propName, propRef, false})
			}
			if propRef.Value.Type.Is("array") && propRef.Value.Items != nil &&
				propRef.Value.Items.Value != nil && propRef.Value.Items.Ref == "" &&
				len(propRef.Value.Items.Value.Enum) > 1 && propRef.Value.Items.Value.Type.Is("string") {
				key := groupKey{
					valueSet: EnumKey(propRef.Value.Items.Value.Enum),
					typeName: extractEnumTypeName(propRef.Value.Items.Value, astEnumMap),
				}
				addUsage(key, enumUsage{schemaName, propName, propRef, true})
			}
		}
	}

	for _, key := range groupOrder {
		usages := enumGroups[key]
		if len(usages) < 2 {
			continue
		}

		enumName, err := deriveEnumName(key.valueSet, key.typeName, usages, astEnumMap)
		if err != nil {
			return err
		}
		if _, exists := doc.Components.Schemas[enumName]; exists {
			return fmt.Errorf("enum name collision: %s already exists as a component schema", enumName)
		}

		var enumValues []any
		if usages[0].inItems {
			enumValues = usages[0].propRef.Value.Items.Value.Enum
		} else {
			enumValues = usages[0].propRef.Value.Enum
		}

		doc.Components.Schemas[enumName] = &openapi3.SchemaRef{
			Value: &openapi3.Schema{
				Type: &openapi3.Types{"string"},
				Enum: enumValues,
			},
		}

		ref := "#/components/schemas/" + enumName

		for _, usage := range usages {
			if usage.inItems {
				usage.propRef.Value.Items = &openapi3.SchemaRef{Ref: ref}
			} else {
				old := usage.propRef.Value
				if old.Description == "" && !old.Deprecated && old.Format == "" {
					usage.propRef.Ref = ref
					usage.propRef.Value = nil
				} else {
					usage.propRef.Value = &openapi3.Schema{
						AllOf: openapi3.SchemaRefs{
							{Ref: ref},
						},
						Description: old.Description,
						Deprecated:  old.Deprecated,
						Format:      old.Format,
					}
				}
			}
		}
	}
	return nil
}

// deriveEnumName looks up a shared enum's Go type name. If typeName is
// non-empty (because we recovered it from x-go-enum-desc), it is used
// directly. Otherwise the value-set must map to exactly one known type. On
// failure, returns an error identifying the offending properties.
func deriveEnumName(key, typeName string, usages []enumUsage, astEnumMap map[string][]string) (string, error) {
	if typeName != "" {
		return typeName, nil
	}
	names := astEnumMap[key]
	if len(names) == 1 {
		return names[0], nil
	}

	props := map[string]bool{}
	for _, u := range usages {
		props[fmt.Sprintf("%s.%s", u.schemaName, u.propName)] = true
	}
	propList := make([]string, 0, len(props))
	for p := range props {
		propList = append(propList, p)
	}
	if len(names) > 1 {
		return "", fmt.Errorf(
			"value-set %q is shared by multiple swagger:enum types %v and could not be disambiguated for properties: %v; "+
				"ensure go-swagger emits x-go-enum-desc for those properties",
			key, names, propList,
		)
	}
	return "", fmt.Errorf(
		"no swagger:enum annotation matches value-set %q used by %d properties: %v; "+
			"fix by adding a named string type with // swagger:enum to modules/structs or modules/commitstatus",
		key, len(usages), propList,
	)
}

// extractEnumTypeName recovers the Go type name a schema's enum came from by
// parsing the property's x-go-enum-desc extension. go-swagger emits one line
// per value as "<value> <ConstName>[ <free text>]"; the type is the longest
// common prefix of the const names, narrowed to the candidate set in
// astEnumMap. Returns "" if extraction is inconclusive.
func extractEnumTypeName(s *openapi3.Schema, astEnumMap map[string][]string) string {
	if s == nil || s.Extensions == nil {
		return ""
	}
	raw, ok := s.Extensions["x-go-enum-desc"]
	if !ok {
		return ""
	}
	desc, ok := raw.(string)
	if !ok {
		return ""
	}
	candidates := astEnumMap[EnumKey(s.Enum)]
	if len(candidates) == 0 {
		return ""
	}
	// Collect the const names (second whitespace-separated field per line).
	var consts []string
	for line := range strings.SplitSeq(desc, "\n") {
		fields := strings.Fields(line)
		if len(fields) >= 2 {
			consts = append(consts, fields[1])
		}
	}
	if len(consts) == 0 {
		return ""
	}
	// A candidate matches when it is a prefix of every const name AND the
	// first character after the prefix is an uppercase ASCII letter — this
	// rejects e.g. "Alpha" matching "Alphabet" (suffix "bet" starts lower)
	// while still accepting both "Alpha" and "AlphaPlus" against "AlphaPlusX"
	// (both prefixes valid). The most specific (longest) wins; ties return
	// "" so deriveEnumName surfaces the ambiguity rather than silently
	// picking a winner.
	ordered := append([]string(nil), candidates...)
	sort.Slice(ordered, func(i, j int) bool { return len(ordered[i]) > len(ordered[j]) })
	var matches []string
	for _, name := range ordered {
		ok := true
		for _, c := range consts {
			if !strings.HasPrefix(c, name) {
				ok = false
				break
			}
			suffix := c[len(name):]
			// Empty suffix means the const name exactly equals the type name — valid exact match.
			// A non-empty suffix must begin with an uppercase letter to reject incidental
			// prefix matches (e.g. "Alpha" should not match "Alphabet").
			if len(suffix) > 0 && (suffix[0] < 'A' || suffix[0] > 'Z') {
				ok = false
				break
			}
		}
		if ok {
			matches = append(matches, name)
		}
	}
	if len(matches) == 0 {
		return ""
	}
	if len(matches) > 1 && len(matches[0]) == len(matches[1]) {
		return ""
	}
	return matches[0]
}