challenge2015 solution | @c-harish

INSTRUCTIONS.md

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+# Challenge 2015
+
+This solution finds the shortest degree of connection between two actors based on their movie collaborations using single source shortest path breadth-first algorithm.
+
+## Prerequisites
+
+- Go 1.23.5 or later
+
+## Installation
+
+1. Clone the repository:
+    ```sh
+    git clone https://github.com/c-harish/challenge2015.git
+    cd challenge2015
+    ```
+
+2. Install dependencies:
+    ```sh
+    go mod tidy
+    ```
+
+## Usage
+
+1. Run the program:
+    ```sh
+    go run main.go
+    ```
+
+2. Enter the source actor's moviebuff URL when prompted:
+    ```
+    source actor : <source_actor_url>
+    ```
+
+3. Enter the target actor's moviebuff URL when prompted:
+    ```
+    target actor : <target_actor_url>
+    ```
+
+Refer to https://www.moviebuff.com/ for valid actor_url
+
+The program will output the degrees of separation and the list movies connecting the two actors.

go.mod

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+module challenge2015
+
+go 1.23.5

main.go

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+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"sync"
+)
+
+type Person struct {
+	Name   string        `json:"name"`
+	URL    string        `json:"url"`
+	Movies []PersonMovie `json:"movies"`
+}
+
+type PersonMovie struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+	Role string `json:"role"`
+}
+
+type Movie struct {
+	Name string        `json:"name"`
+	URL  string        `json:"url"`
+	Cast []MoviePerson `json:"cast"`
+	Crew []MoviePerson `json:"crew"`
+}
+
+type MoviePerson struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+	Role string `json:"role"`
+}
+
+var cache = make(map[string]interface{})
+var cacheLock = &sync.Mutex{}
+
+func fetchData(url string) ([]byte, error) {
+	resp, err := http.Get("https://data.moviebuff.com/" + url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	return io.ReadAll(resp.Body)
+}
+
+type Path struct {
+	Depth []Step
+}
+
+type Step struct {
+	Movie  string
+	Role   string
+	Person string
+}
+
+func findConnection(start, end string) (*Path, error) {
+	// Find Shortest Path from single source using BFS with Queue iteratively
+	visited := make(map[string]bool)
+	queue := make([]Path, 0)
+
+	queue = append(queue, Path{Depth: []Step{}})
+	visited[start] = true
+
+	for len(queue) > 0 {
+		currentPath := queue[0]
+		queue = queue[1:]
+
+		currentPerson := start
+		if len(currentPath.Depth) > 0 {
+			currentPerson = currentPath.Depth[len(currentPath.Depth)-1].Person
+		}
+
+		// Check if data exists in cache before making API call
+		var person Person
+		data, exists := cache[currentPerson]
+		if !exists {
+			rawData, err := fetchDataAsync(currentPerson)
+			if err != nil {
+				continue
+			}
+			if err := json.Unmarshal(rawData, &person); err != nil {
+				continue
+			}
+			// Store the response in Cache for future use
+			// Using Lock to make map thread-safe
+			cacheLock.Lock()
+			cache[currentPerson] = person
+			cacheLock.Unlock()
+		} else {
+			person = data.(Person)
+		}
+
+		var wg sync.WaitGroup
+		movieChan := make(chan Movie, len(person.Movies))
+
+		for _, movie := range person.Movies {
+			wg.Add(1)
+			// Fetching movie data asynchronously by spawning goroutine
+			go func(movie PersonMovie) {
+				defer wg.Done()
+				var movieData Movie
+				data, exists := cache[movie.URL]
+				if !exists {
+					rawData, err := fetchDataAsync(movie.URL)
+					if err != nil {
+						return
+					}
+					if err := json.Unmarshal(rawData, &movieData); err != nil {
+						return
+					}
+					cacheLock.Lock()
+					cache[movie.URL] = movieData
+					cacheLock.Unlock()
+				} else {
+					movieData = data.(Movie)
+				}
+				movieChan <- movieData
+			}(movie)
+		}
+
+		go func() {
+			wg.Wait()
+			close(movieChan)
+		}()
+
+		for movieData := range movieChan {
+			// Check in both cast and crew of the movie for connections
+			for _, p := range append(movieData.Cast, movieData.Crew...) {
+				if visited[p.URL] {
+					continue
+				}
+
+				visited[p.URL] = true
+
+				newPath := Path{
+					Depth: append(currentPath.Depth, Step{
+						Movie:  movieData.Name,
+						Role:   p.Role,
+						Person: p.URL,
+					}),
+				}
+
+				if p.URL == end {
+					return &newPath, nil
+				}
+
+				queue = append(queue, newPath)
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("connection error")
+}
+
+func fetchDataAsync(url string) ([]byte, error) {
+	dataChan := make(chan []byte, 1)
+	errChan := make(chan error, 1)
+
+	go func() {
+		data, err := fetchData(url)
+		if err != nil {
+			errChan <- err
+			return
+		}
+		dataChan <- data
+	}()
+
+	select {
+	case data := <-dataChan:
+		return data, nil
+	case err := <-errChan:
+		return nil, err
+	}
+}
+
+func main() {
+	var person1, person2 string
+
+	fmt.Print("source actor : ")
+	fmt.Scanf("%s", &person1)
+	fmt.Print("target actor : ")
+	fmt.Scanf("%s", &person2)
+	path, err := findConnection(person1, person2)
+	if err != nil {
+		fmt.Println("Error:", err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("\nDegrees of Separation: %d\n\n", len(path.Depth))
+	for i, step := range path.Depth {
+		fmt.Printf("%d. Movie: %s\n", i+1, step.Movie)
+		if i == 0 {
+			fmt.Printf("   %s: %s\n", step.Role, person1)
+		} else {
+			fmt.Printf("   %s: %s\n", path.Depth[i-1].Role, path.Depth[i-1].Person)
+		}
+		fmt.Printf("   %s: %s\n", step.Role, step.Person)
+	}
+}