package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"path/filepath"
	"strings"
	"time"

	s3 "github.com/minio/minio-go/v7"
)

// parseDocsRequestPath parses paths like:
// /docs/<namespace>/<name>/<version>/...  (rest may be empty)
func parseDocsRequestPath(p string) (namespace, name, version, rest string, err error) {
	p = strings.TrimPrefix(p, "/")
	p = strings.TrimPrefix(p, "docs/")
	parts := strings.SplitN(p, "/", 4)
	if len(parts) < 3 {
		err = fmt.Errorf("invalid docs path: %s", p)
		return
	}
	namespace = parts[0]
	name = parts[1]
	version = parts[2]
	if len(parts) == 3 {
		rest = ""
	} else {
		rest = parts[3]
	}
	return
}

// docsObjectKey builds the S3 key for a docs object given parsed parts.
func docsObjectKey(namespace, name, version, pathPart string) string {
	clean := strings.TrimPrefix(pathPart, "/")
	if clean == "" {
		return fmt.Sprintf("docs/%s/%s/%s/index.html", namespace, name, version)
	}
	return fmt.Sprintf("docs/%s/%s/%s/%s", namespace, name, version, clean)
}

// tryCandidateKeys returns a list of keys to attempt for a given request path.
// Order matters: exact path first, then <path>/index.html, then top-level index.
func tryCandidateKeys(namespace, name, version, rest string) []string {
	keys := []string{}
	if rest == "" {
		keys = append(keys, docsObjectKey(namespace, name, version, "index.html"))
		return keys
	}
	// exact
	keys = append(keys, docsObjectKey(namespace, name, version, rest))
	// if it looks like a directory or has no extension, try index under it
	if strings.HasSuffix(rest, "/") || filepath.Ext(rest) == "" {
		keys = append(keys, docsObjectKey(namespace, name, version, strings.TrimSuffix(rest, "/")+"/index.html"))
	}
	// finally, try root index
	keys = append(keys, docsObjectKey(namespace, name, version, "index.html"))
	return keys
}

// docsHandler serves static documentation files from S3 (public-facing via Ingress).
func docsHandler(w http.ResponseWriter, r *http.Request) {
	ns, name, ver, rest, err := parseDocsRequestPath(r.URL.Path)
	if err != nil {
		http.Error(w, "Bad docs path", http.StatusBadRequest)
		return
	}

	ctx := context.Background()
	candidates := tryCandidateKeys(ns, name, ver, rest)
	log.Printf("Docs candidates (host=%s): %v", hostname, candidates)

	var lastErr error
	for _, key := range candidates {
		_, err := s3Client.StatObject(ctx, bucketName, key, s3.GetObjectOptions{})
		if err != nil {
			lastErr = err
			continue
		}

		presigned, err := s3Client.PresignedGetObject(ctx, bucketName, key, 15*time.Minute, nil)
		if err != nil {
			lastErr = err
			continue
		}
		http.Redirect(w, r, presigned.String(), http.StatusFound)
		return
	}

	log.Printf("Docs not found in candidates: %v, lastErr: %v", candidates, lastErr)
	http.Error(w, "Documentation not found", http.StatusNotFound)
}