package auth

import (
	"errors"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"

	"github.com/geo-platform/tenant-api/internal/shared/response"
)

const authRequestLogContextKey = "auth_request_log_context"

type RequestLogContext struct {
	HeaderPresent    bool
	Scheme           string
	TokenFingerprint string
	FailureStage     string
	FailureReason    string
	ParseError       string
	TokenSubject     string
	TokenExpiresAt   string
}

func Middleware(jwtMgr *Manager, sessions *SessionStore) gin.HandlerFunc {
	return func(c *gin.Context) {
		header := c.GetHeader("Authorization")
		updateRequestLogContext(c, func(meta *RequestLogContext) {
			meta.HeaderPresent = strings.TrimSpace(header) != ""
			meta.Scheme = authorizationScheme(header)
		})

		raw, err := bearerToken(header)
		if err != nil {
			updateRequestLogContext(c, func(meta *RequestLogContext) {
				meta.FailureStage = "read_bearer_token"
				meta.FailureReason = bearerHeaderFailureReason(header)
			})
			response.Error(c, response.ErrUnauthorized(40101, "missing_bearer_token", "Authorization header is required"))
			c.Abort()
			return
		}
		updateRequestLogContext(c, func(meta *RequestLogContext) {
			meta.TokenFingerprint = tokenFingerprint(raw)
		})

		claims, err := jwtMgr.Parse(raw)
		if err != nil {
			updateRequestLogContext(c, func(meta *RequestLogContext) {
				meta.FailureStage = "parse_access_token"
				meta.FailureReason = accessTokenFailureReason(err)
				meta.ParseError = err.Error()
			})
			response.Error(c, response.ErrUnauthorized(40102, "invalid_access_token", "token is invalid or expired"))
			c.Abort()
			return
		}

		updateRequestLogContext(c, func(meta *RequestLogContext) {
			meta.TokenSubject = strings.TrimSpace(claims.Subject)
			if claims.ExpiresAt != nil {
				meta.TokenExpiresAt = claims.ExpiresAt.Time.UTC().Format(time.RFC3339)
			}
		})

		if claims.Subject != "access" {
			updateRequestLogContext(c, func(meta *RequestLogContext) {
				meta.FailureStage = "validate_access_subject"
				meta.FailureReason = "wrong_subject"
			})
			response.Error(c, response.ErrUnauthorized(40102, "invalid_access_token", "token is invalid or expired"))
			c.Abort()
			return
		}

		revoked, _ := sessions.IsBlacklisted(c.Request.Context(), claims.ID)
		if revoked {
			updateRequestLogContext(c, func(meta *RequestLogContext) {
				meta.FailureStage = "check_blacklist"
				meta.FailureReason = "blacklisted"
			})
			response.Error(c, response.ErrUnauthorized(40103, "token_revoked", "token has been logged out"))
			c.Abort()
			return
		}

		actor := Actor{
			UserID:             claims.UserID,
			TenantID:           claims.TenantID,
			PrimaryWorkspaceID: claims.PrimaryWorkspaceID,
			Role:               claims.Role,
		}
		c.Request = c.Request.WithContext(WithActor(c.Request.Context(), actor))
		c.Next()
	}
}

func bearerToken(header string) (string, error) {
	parts := strings.SplitN(header, " ", 2)
	if len(parts) != 2 || !strings.EqualFold(parts[0], "bearer") {
		return "", response.ErrUnauthorized(40101, "missing_bearer_token", "Authorization header is required")
	}
	return parts[1], nil
}

func RequestLogContextFromGin(c *gin.Context) (RequestLogContext, bool) {
	if c == nil {
		return RequestLogContext{}, false
	}

	value, ok := c.Get(authRequestLogContextKey)
	if !ok || value == nil {
		return RequestLogContext{}, false
	}

	meta, ok := value.(*RequestLogContext)
	if !ok || meta == nil {
		return RequestLogContext{}, false
	}

	return *meta, true
}

func updateRequestLogContext(c *gin.Context, apply func(*RequestLogContext)) {
	if c == nil || apply == nil {
		return
	}

	value, ok := c.Get(authRequestLogContextKey)
	if ok {
		if meta, ok := value.(*RequestLogContext); ok && meta != nil {
			apply(meta)
			return
		}
	}

	meta := &RequestLogContext{}
	apply(meta)
	c.Set(authRequestLogContextKey, meta)
}

func authorizationScheme(header string) string {
	parts := strings.Fields(strings.TrimSpace(header))
	if len(parts) == 0 {
		return ""
	}
	return parts[0]
}

func bearerHeaderFailureReason(header string) string {
	trimmed := strings.TrimSpace(header)
	if trimmed == "" {
		return "missing_authorization_header"
	}

	parts := strings.Fields(trimmed)
	if len(parts) == 0 {
		return "missing_authorization_header"
	}
	if !strings.EqualFold(parts[0], "bearer") {
		return "invalid_authorization_scheme"
	}
	if len(parts) == 1 {
		return "missing_token_after_bearer"
	}
	return "malformed_authorization_header"
}

func accessTokenFailureReason(err error) string {
	switch {
	case err == nil:
		return ""
	case errors.Is(err, jwt.ErrTokenExpired):
		return "expired"
	case errors.Is(err, jwt.ErrTokenNotValidYet):
		return "not_valid_yet"
	case errors.Is(err, jwt.ErrTokenMalformed):
		return "malformed"
	case errors.Is(err, jwt.ErrTokenSignatureInvalid):
		return "bad_signature"
	case errors.Is(err, jwt.ErrTokenUnverifiable):
		return "unverifiable"
	case errors.Is(err, jwt.ErrTokenInvalidClaims):
		return "invalid_claims"
	default:
		return "parse_failed"
	}
}

func tokenFingerprint(raw string) string {
	if strings.TrimSpace(raw) == "" {
		return ""
	}

	hashed := HashToken(raw)
	if len(hashed) > 16 {
		return hashed[:16]
	}
	return hashed
}