Environment Setup

1. Install Rust from https://rustup.rs/
2. Install Solana v1.6.2 or later from https://docs.solana.com/cli/install-solana-cli-tools#use-solanas-install-tool

Build and test for program compiled natively

$ cargo build
$ cargo test

Build and test the program compiled for BPF

$ cargo build-bpf
$ cargo test-bpf

What is an escrow?

• Simply putting, escrow is the use of a third party which holds assets or funds before they're transferred from one party to another.
• An escrow will hold the assets or funds until both parties have fulfilled their contractual requirements.
• Types of escrow: real estate escrow, stock market escrow, online sale escrow, etc.

What is smart contract?

• Smart contract is a set of promises written in digital form, including protocols (math or standard operating procedures (if, else)) within which the parties perform on these promises. (Nick Szabo, 1996)
• Smart contract may not be smart: just algorithms that perform a function, not artificial intelligence.
• Smart contract may not be contract.
• Use cases of smart contracts for business: digital identity, records, securities, trade finance, derivatives, financial data recording, mortages, land title recording, supply chain, auto insurance, clinical trials, cancer research, etc.

What is dApp?

• dApp stands for decentralized applications which use blockchain as data storage and most of them have their own native token. dApps run as a smart contract on top of a platform.
• You can visit State of dApps or Dappradar for more information about dApps and according to the former site, more than half of all the dApps listed fail!
• Usage of dApps: exchange, gambling, gaming, finance, etc.
• By the time I write this README, the most active dApp has 2,050 active users per day compared to Facebook with half a billion active users a day.
• Why haven't dApps yet received wide consumer adoption?

What is Solana?

• Solana is high performance, single-layer, permissionless open-source blockchain. In other words, Solana is a data storage for dApps.
• Solana's native token is SOL and it can be divisible by up to one billion. 1e-9 SOL = 1 lamport.
• The Solana ecosystem is still young and the platform just went to mainnet in March 2020

Common way to structure a Solana's program

.
├─ src
│  ├─ lib.rs -> registering modules
│  ├─ entrypoint.rs -> entrypoint to the program
│  ├─ instruction.rs -> program API, (de)serializing instruction data
│  ├─ processor.rs -> program logic
│  ├─ state.rs -> program objects, (de)serializing state
│  ├─ error.rs -> program specific errors
├─ .gitignore
├─ Cargo.lock
├─ Cargo.toml
├─ Xargo.toml

The flow of a smart contract if you use the above structure:

1. A client sends a request to the smart contract.
2. The entrypoint receives the requests.
3. The entrypoint forwards the arguments to the processor.
4. The processor asks the instruction.rs to decode the instruction_data argument provided by the entrypoint.
5. With the decoded data, the processor decides which processing function to use to process the request.
6. The process may use the state.rs to encode the state into or decode the state of an account which has been passed into the entrypoint.