### URL Parser

Link: https://crates.io/crates/url_parser Docs: https://docs.rs/url_parser/0.1.0/url_parser/

URL Parser is a Rust parser developed to parse URLs into structured components such as scheme, domain, path, query and fragment.

### Parsing Process

URL Parser processes a URL string and extracts the following components:

1. **Scheme**: The protocol used (for example, "http", "https").
2. **Domain**: The domain name or IP address of the URL (for example, "example.com").
3. **Path**: The path that specifies the resource location on the server (for example, "/products/electronics").
4. **Query**: The query string following a '?', used for passing parameters (for example, "?query=1").
5. **Fragment**: The section identifier following a '#', referring to a part of the resource (for example, "#reviews").

The parsed components are essential for applications needing to analyze, validate or manipulate URLs.

### Grammar

### url

```
url = { scheme ~ "://" ~ domain ~ path? ~ query? ~ fragment? }
```

**Purpose**: Defines the overall structure of the URL.

**Explanation**: The url rule is the basic rule for parsing a full URL. It expects:

1. scheme followed by ://
2. domain
3. optional path
4. optional query
5. optional fragment

'?' after some components (path?, query?, fragment?) means that these components are optional.

### scheme

```
scheme = @{ ASCII_ALPHANUMERIC+ }
```

**Purpose**: Identifies the URL scheme or protocol (for example, "http", "https", "ftp").

**Explanation**: A scheme rule matches one or more alphanumeric characters (letters and numbers). The '@' symbol marks this rule as an atomic rule, which means that it is processed as a single unit to improve performance and ensure correct parsing.

### domain

```
domain = @{ (!("/" | "?") ~ ANY)+ }
```

**Purpose**: Defines the domain part of the URL (for example, "example.com", "localhost", "192.168.0.1").

**Explanation**: The domain rule finds one or more characters that are not the '/' or '?' character. The ANY keyword matches any character other than a newline. This allows the domain to include subdomains, IP addresses or hostnames, as long as they do not contain '/' or '?'.

### path

```
path = { "/" ~ (!("?" | "#") ~ ANY)* }
```

**Purpose**: Defines a component of a URL path that indicates the location of a resource on the server (for example, "/products/electronics").

**Explanation**: The path rule begins with '/' and then allows zero or more characters that are not the '?' or '#' character. This excludes query parameters and fragment identifiers from the path part.

### query

```
query = { "?" ~ (!"#" ~ ANY)* }
```

**Purpose**: Defines a query string in the URL that is typically used to pass parameters (for example, "?query=1").

**Explanation**: The query rule starts with '?' and allows zero or more characters that are not '#'. This ensures that the query string does not include a fragment character (#) that belongs to a URL fragment component.

### fragment

```
fragment = { "#" ~ ANY* }
```

**Purpose**: Defines a section identifier that points to a specific section within the resource (for example, "#reviews").

**Explanation**: The fragment rule starts with '#' and allows any number of characters after it. This rule allows the fragment to contain any characters after the '#'.