package handler

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"mime"
	"net/http"
	"strconv"
	"strings"
	"sync/atomic"
	"time"

	"git.ilapage.cn/OPC/chorus/internal/core/model"
	"git.ilapage.cn/OPC/chorus/portal/openapi"
	"git.ilapage.cn/OPC/chorus/portal/service"
	"github.com/gin-gonic/gin"
)

const openAPIPrincipalContextKey = "openapi_principal"

var openAPIRequestIDCounter atomic.Uint64

func (h *Handler) openAPIHeaders(c *gin.Context) {
	noStore(c)
	c.Next()
}

func newOpenAPIRequestID() string {
	requestID := make([]byte, 16)
	if _, err := rand.Read(requestID); err == nil {
		return hex.EncodeToString(requestID)
	}
	return fmt.Sprintf("%x-%x", time.Now().UTC().UnixNano(), openAPIRequestIDCounter.Add(1))
}

func (h *Handler) requireAPIKey(c *gin.Context) {
	if c.GetHeader("Cookie") != "" || hasCredentialQuery(c) {
		h.invalidAPIKey(c)
		return
	}
	headers := c.Request.Header.Values("Authorization")
	if len(headers) != 1 {
		h.invalidAPIKey(c)
		return
	}
	parts := strings.Fields(headers[0])
	if len(parts) != 2 || !strings.EqualFold(parts[0], "Bearer") {
		h.invalidAPIKey(c)
		return
	}
	principal, err := h.service.AuthenticateAPIKey(c.Request.Context(), parts[1], time.Now().UTC())
	if err != nil {
		if errors.Is(err, service.ErrInvalidAPIKeyCredential) {
			h.invalidAPIKey(c)
			return
		}
		writeError(c, http.StatusInternalServerError, "internal_error", "request could not be completed")
		c.Abort()
		return
	}
	c.Set(openAPIPrincipalContextKey, principal)
	c.Next()
}

func (h *Handler) invalidAPIKey(c *gin.Context) {
	c.Header("WWW-Authenticate", "Bearer")
	writeError(c, http.StatusUnauthorized, "invalid_api_key", "API key is missing or invalid")
	c.Abort()
}

func hasCredentialQuery(c *gin.Context) bool {
	for name := range c.Request.URL.Query() {
		for _, credentialName := range []string{"api_key", "access_token", "token", "authorization"} {
			if strings.EqualFold(name, credentialName) {
				return true
			}
		}
	}
	return false
}

func currentAPIPrincipal(c *gin.Context) service.APIPrincipal {
	value, _ := c.Get(openAPIPrincipalContextKey)
	principal, _ := value.(service.APIPrincipal)
	return principal
}

func (h *Handler) openAPISpec(c *gin.Context) {
	if !requireNoQuery(c) {
		return
	}
	c.Data(http.StatusOK, "application/json; charset=utf-8", openapi.Spec())
}

func (h *Handler) openAPISubmitText(c *gin.Context) {
	if !requireNoQuery(c) {
		return
	}
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 64<<10)
	var input struct {
		Prompt string `json:"prompt"`
	}
	if !decodeOpenAPIJSON(c, &input) {
		return
	}
	idempotencyKey, ok := openAPIIdempotencyKey(c)
	if !ok {
		return
	}
	principal := currentAPIPrincipal(c)
	generation, created, err := h.service.SubmitText(c.Request.Context(), principal.UserID, idempotencyKey, input.Prompt)
	if err != nil {
		h.serviceError(c, err)
		return
	}
	status := http.StatusAccepted
	if !created {
		status = http.StatusOK
	}
	c.Set(auditGenerationIDContextKey, generation.ID)
	c.Set(auditGenerationCreatedContextKey, created)
	c.JSON(status, openAPIGenerationResponse(generation))
}

func decodeOpenAPIJSON(c *gin.Context, target any) bool {
	if mediaType, _, err := mime.ParseMediaType(c.GetHeader("Content-Type")); err != nil || mediaType != "application/json" {
		writeError(c, http.StatusBadRequest, "invalid_request", "request body is invalid")
		return false
	}
	decoder := json.NewDecoder(c.Request.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(target); err != nil || decoder.Decode(&struct{}{}) != io.EOF {
		writeError(c, http.StatusBadRequest, "invalid_request", "request body is invalid")
		return false
	}
	return true
}

func (h *Handler) openAPISubmitImages(c *gin.Context) {
	if !requireNoQuery(c) {
		return
	}
	mediaType, _, err := mime.ParseMediaType(c.GetHeader("Content-Type"))
	if err != nil || mediaType != "multipart/form-data" {
		writeError(c, http.StatusBadRequest, "invalid_request", "request body is invalid")
		return
	}
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, h.maxUploadBytes+(1<<20))
	if err := c.Request.ParseMultipartForm(h.maxUploadBytes); err != nil {
		writeError(c, http.StatusBadRequest, "upload_too_large", "upload exceeds configured limit")
		return
	}
	defer c.Request.MultipartForm.RemoveAll()
	if !exactMultipartValues(c, "prompt", "metadata") {
		writeError(c, http.StatusBadRequest, "invalid_request", "multipart fields are invalid")
		return
	}
	var input struct {
		Capability *model.Capability     `json:"capability"`
		RoleRule   *string               `json:"role_rule"`
		Images     *[]service.ImageInput `json:"images"`
	}
	decoder := json.NewDecoder(strings.NewReader(c.Request.MultipartForm.Value["metadata"][0]))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil || decoder.Decode(&struct{}{}) != io.EOF || input.Capability == nil || input.RoleRule == nil || input.Images == nil {
		writeError(c, http.StatusBadRequest, "invalid_metadata", "image metadata is invalid")
		return
	}
	metadata := service.ImageMetadata{Capability: *input.Capability, RoleRule: *input.RoleRule, Images: *input.Images}
	uploads, ok := h.openAPIUploads(c, metadata)
	if !ok {
		return
	}
	idempotencyKey, ok := openAPIIdempotencyKey(c)
	if !ok {
		return
	}
	principal := currentAPIPrincipal(c)
	generation, created, submitErr := h.service.SubmitImages(c.Request.Context(), principal.UserID, idempotencyKey, c.Request.MultipartForm.Value["prompt"][0], metadata, uploads)
	if submitErr != nil {
		h.serviceError(c, submitErr)
		return
	}
	status := http.StatusAccepted
	if !created {
		status = http.StatusOK
	}
	c.Set(auditGenerationIDContextKey, generation.ID)
	c.Set(auditGenerationCreatedContextKey, created)
	c.JSON(status, openAPIGenerationResponse(generation))
}

func exactMultipartValues(c *gin.Context, required ...string) bool {
	if len(c.Request.MultipartForm.Value) != len(required) {
		return false
	}
	for _, name := range required {
		if values := c.Request.MultipartForm.Value[name]; len(values) != 1 {
			return false
		}
	}
	return true
}

func (h *Handler) openAPIUploads(c *gin.Context, metadata service.ImageMetadata) ([]service.Upload, bool) {
	expectedFields := make(map[string]string, len(metadata.Images))
	for _, item := range metadata.Images {
		field := "files[" + item.ClientID + "]"
		if _, exists := expectedFields[field]; exists {
			writeError(c, http.StatusBadRequest, "invalid_image_mapping", "image files do not match metadata")
			return nil, false
		}
		expectedFields[field] = item.ClientID
	}
	if len(c.Request.MultipartForm.File) != len(expectedFields) {
		writeError(c, http.StatusBadRequest, "invalid_image_mapping", "image files do not match metadata")
		return nil, false
	}
	uploads := make([]service.Upload, 0, len(expectedFields))
	for field, clientID := range expectedFields {
		headers := c.Request.MultipartForm.File[field]
		if len(headers) != 1 {
			writeError(c, http.StatusBadRequest, "invalid_image_mapping", "image files do not match metadata")
			return nil, false
		}
		header := headers[0]
		file, err := header.Open()
		if err != nil {
			writeFileError(c, int(metadataPosition(metadata, clientID)), safeName(header.Filename), "invalid_image_content")
			return nil, false
		}
		content, readErr := io.ReadAll(io.LimitReader(file, h.maxUploadBytes+1))
		closeErr := file.Close()
		if readErr != nil || closeErr != nil {
			writeFileError(c, int(metadataPosition(metadata, clientID)), safeName(header.Filename), "invalid_image_content")
			return nil, false
		}
		uploads = append(uploads, service.Upload{ClientID: clientID, Name: header.Filename, DeclaredMIME: header.Header.Get("Content-Type"), Content: content})
	}
	return uploads, true
}

func (h *Handler) openAPIHistory(c *gin.Context) {
	if !queryNamesAllowed(c, "limit", "cursor") {
		writeError(c, http.StatusBadRequest, "invalid_request", "query parameters are invalid")
		return
	}
	limit := h.service.DefaultHistoryLimit()
	if values, exists := c.GetQueryArray("limit"); exists {
		if len(values) != 1 {
			writeError(c, http.StatusBadRequest, "invalid_limit", "history limit is invalid")
			return
		}
		parsed, parseErr := strconv.Atoi(values[0])
		if parseErr != nil {
			writeError(c, http.StatusBadRequest, "invalid_limit", "history limit is invalid")
			return
		}
		limit = parsed
	}
	cursor := ""
	if values, exists := c.GetQueryArray("cursor"); exists {
		if len(values) != 1 || values[0] == "" {
			writeError(c, http.StatusBadRequest, "invalid_cursor", "history cursor is invalid")
			return
		}
		cursor = values[0]
	}
	page, err := h.service.History(c.Request.Context(), currentAPIPrincipal(c).UserID, limit, cursor)
	if err != nil {
		h.serviceError(c, err)
		return
	}
	items := make([]gin.H, 0, len(page.Items))
	for _, row := range page.Items {
		items = append(items, openAPIGenerationResponse(row))
	}
	c.JSON(http.StatusOK, gin.H{"items": items, "next_cursor": page.NextCursor, "has_more": page.HasMore})
}

func queryNamesAllowed(c *gin.Context, allowed ...string) bool {
	set := make(map[string]struct{}, len(allowed))
	for _, name := range allowed {
		set[name] = struct{}{}
	}
	for name := range c.Request.URL.Query() {
		if _, ok := set[name]; !ok {
			return false
		}
	}
	return true
}

func requireNoQuery(c *gin.Context) bool {
	if queryNamesAllowed(c) {
		return true
	}
	writeError(c, http.StatusBadRequest, "invalid_request", "query parameters are invalid")
	return false
}

func openAPIIdempotencyKey(c *gin.Context) (string, bool) {
	values := c.Request.Header.Values("Idempotency-Key")
	if len(values) != 1 {
		writeError(c, http.StatusBadRequest, "invalid_idempotency_key", "idempotency key is invalid")
		return "", false
	}
	return values[0], true
}

func (h *Handler) openAPIDetail(c *gin.Context) {
	if !queryNamesAllowed(c) {
		writeError(c, http.StatusBadRequest, "invalid_request", "query parameters are invalid")
		return
	}
	id, ok := uintParam(c, "id")
	if !ok {
		return
	}
	detail, err := h.service.ByID(c.Request.Context(), currentAPIPrincipal(c).UserID, id)
	if err != nil {
		h.serviceError(c, err)
		return
	}
	response := openAPIGenerationResponse(detail.Generation)
	inputs := make([]gin.H, 0, len(detail.Inputs))
	for _, input := range detail.Inputs {
		inputs = append(inputs, gin.H{"id": input.ID, "position": input.Position, "role": input.Role, "note": input.Note, "name": input.OriginalName, "mime_type": input.MIMEType, "size_bytes": input.SizeBytes, "width": input.Width, "height": input.Height, "url": fmt.Sprintf("/openapi/v1/generations/%d/inputs/%d", id, input.ID)})
	}
	outputs := make([]gin.H, 0, len(detail.Outputs))
	for _, output := range detail.Outputs {
		item := gin.H{"id": output.ID, "kind": output.Kind, "mime_type": output.MIMEType, "size_bytes": output.SizeBytes, "width": output.Width, "height": output.Height, "created_at": output.CreatedAt.UTC()}
		if output.TextContent != nil {
			item["text"] = *output.TextContent
		}
		if output.StorageKey != nil {
			item["url"] = fmt.Sprintf("/openapi/v1/generations/%d/outputs/%d", id, output.ID)
			if output.ThumbnailStorageKey != nil {
				item["thumbnail_url"] = fmt.Sprintf("/openapi/v1/generations/%d/outputs/%d/thumbnail", id, output.ID)
			}
		}
		outputs = append(outputs, item)
	}
	response["role_rule"] = detail.Generation.RoleRule
	response["inputs"] = inputs
	response["outputs"] = outputs
	c.JSON(http.StatusOK, response)
}

func (h *Handler) openAPIInput(c *gin.Context) {
	generationID, inputID, ok := openAPIFileIDs(c, "inputID")
	if !ok {
		return
	}
	reader, object, name, err := h.service.OpenInput(c.Request.Context(), currentAPIPrincipal(c).UserID, generationID, inputID)
	if err != nil {
		h.serviceError(c, err)
		return
	}
	defer reader.Close()
	c.Header("Content-Type", object.ContentType)
	c.Header("Content-Disposition", mime.FormatMediaType("inline", map[string]string{"filename": name}))
	c.Status(http.StatusOK)
	_, _ = io.Copy(c.Writer, reader)
}

func (h *Handler) openAPIOutput(c *gin.Context)    { h.writeOpenAPIOutput(c, false) }
func (h *Handler) openAPIThumbnail(c *gin.Context) { h.writeOpenAPIOutput(c, true) }

func (h *Handler) writeOpenAPIOutput(c *gin.Context, thumbnail bool) {
	generationID, outputID, ok := openAPIFileIDs(c, "outputID")
	if !ok {
		return
	}
	reader, object, err := h.service.OpenOutput(c.Request.Context(), currentAPIPrincipal(c).UserID, generationID, outputID, thumbnail)
	if err != nil {
		h.serviceError(c, err)
		return
	}
	defer reader.Close()
	c.Header("Content-Type", object.ContentType)
	c.Header("Content-Disposition", "inline")
	c.Status(http.StatusOK)
	_, _ = io.Copy(c.Writer, reader)
}

func openAPIFileIDs(c *gin.Context, resourceName string) (uint64, uint64, bool) {
	if !queryNamesAllowed(c) {
		writeError(c, http.StatusBadRequest, "invalid_request", "query parameters are invalid")
		return 0, 0, false
	}
	generationID, ok := uintParam(c, "id")
	if !ok {
		return 0, 0, false
	}
	resourceID, ok := uintParam(c, resourceName)
	return generationID, resourceID, ok
}

func openAPIGenerationResponse(generation model.Generation) gin.H {
	response := generationResponse(generation)
	response["created_at"] = generation.CreatedAt.UTC()
	if generation.CompletedAt != nil {
		completedAt := generation.CompletedAt.UTC()
		response["completed_at"] = completedAt
	}
	return response
}