scope-bca-core 0.8.6

//! # ABI Parsing and Function Signature Decoding
//!
//! Provides function selector lookup via 4byte.directory and ABI-based
//! parameter decoding for transaction calldata.
//!
//! ## Function Signature Resolution
//!
//! 1. If contract ABI is available (verified source), decode directly from ABI
//! 2. Otherwise, look up the 4-byte selector on 4byte.directory (free, no API key)
//! 3. Fallback: display raw selector hex
//!
//! ## Calldata Decoding
//!
//! For verified contracts with ABI, decodes full calldata parameters using
//! ABI type information. For unverified contracts, only the function name
//! is resolved from the selector.

use crate::contract::source::{AbiEntry, ContractSource};
use serde::Deserialize;

/// A decoded function call from transaction input data.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct DecodedCall {
    /// 4-byte selector (e.g., "0xa9059cbb").
    pub selector: String,
    /// Function signature (e.g., "transfer(address,uint256)").
    pub signature: String,
    /// Human-readable function name (e.g., "transfer").
    pub function_name: String,
    /// Decoded parameters (if ABI available).
    pub parameters: Vec<DecodedParam>,
    /// Whether the decoding came from verified ABI or 4byte.directory.
    pub source: DecodeSource,
}

/// Source of the function signature resolution.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub enum DecodeSource {
    /// Decoded from contract's verified ABI.
    VerifiedAbi,
    /// Looked up from 4byte.directory.
    FourByteDirectory,
    /// Only raw selector available.
    Unknown,
}

/// A decoded parameter from calldata.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct DecodedParam {
    /// Parameter name (from ABI, or "arg0", "arg1" if unknown).
    pub name: String,
    /// Solidity type.
    pub param_type: String,
    /// Decoded value as string.
    pub value: String,
}

/// 4byte.directory API response.
#[derive(Deserialize)]
struct FourByteResponse {
    results: Vec<FourByteResult>,
}

#[derive(Deserialize)]
struct FourByteResult {
    text_signature: String,
}

/// OpenChain (Samczsun) signature lookup response.
#[derive(Deserialize)]
struct OpenChainResponse {
    ok: bool,
    result: Option<OpenChainResult>,
}

#[derive(Deserialize)]
struct OpenChainResult {
    function: Option<std::collections::HashMap<String, Vec<OpenChainEntry>>>,
}

#[derive(Deserialize)]
struct OpenChainEntry {
    name: String,
}

/// Decode transaction input data using available sources.
///
/// Resolution order:
/// 1. ABI from verified source (most accurate)
/// 2. OpenChain/Samczsun signature database
/// 3. 4byte.directory
/// 4. Raw selector fallback
pub async fn decode_calldata(
    input: &str,
    contract_source: Option<&ContractSource>,
    http_client: &dyn crate::http::HttpClient,
) -> DecodedCall {
    if input.is_empty() || input == "0x" {
        return DecodedCall {
            selector: "0x".to_string(),
            signature: "()".to_string(),
            function_name: "Native Transfer".to_string(),
            parameters: vec![],
            source: DecodeSource::Unknown,
        };
    }

    let selector = if input.len() >= 10 {
        &input[..10]
    } else {
        input
    };

    // Try ABI-based decoding first
    if let Some(source) = contract_source
        && let Some(entry) = find_abi_by_selector(selector, &source.parsed_abi)
    {
        let params = decode_params_from_abi(input, entry);
        return DecodedCall {
            selector: selector.to_string(),
            signature: entry.signature(),
            function_name: entry.name.clone(),
            parameters: params,
            source: DecodeSource::VerifiedAbi,
        };
    }

    // Try OpenChain (Samczsun) lookup
    if let Some(sig) = lookup_openchain(selector, http_client).await {
        let fn_name = sig.split('(').next().unwrap_or(&sig).to_string();
        return DecodedCall {
            selector: selector.to_string(),
            signature: sig,
            function_name: fn_name,
            parameters: vec![],
            source: DecodeSource::FourByteDirectory,
        };
    }

    // Try 4byte.directory lookup
    if let Some(sig) = lookup_4byte(selector, http_client).await {
        let fn_name = sig.split('(').next().unwrap_or(&sig).to_string();
        return DecodedCall {
            selector: selector.to_string(),
            signature: sig,
            function_name: fn_name,
            parameters: vec![],
            source: DecodeSource::FourByteDirectory,
        };
    }

    // Fallback: raw selector
    DecodedCall {
        selector: selector.to_string(),
        signature: format!("{}(...)", selector),
        function_name: selector.to_string(),
        parameters: vec![],
        source: DecodeSource::Unknown,
    }
}

/// Look up a function signature on OpenChain (Samczsun's database).
async fn lookup_openchain(
    selector: &str,
    http_client: &dyn crate::http::HttpClient,
) -> Option<String> {
    let url = format!(
        "https://api.openchain.xyz/signature-database/v1/lookup?function={}&filter=true",
        selector
    );

    let response = http_client
        .send(crate::http::Request::get(&url))
        .await
        .ok()?;
    let body: OpenChainResponse = response.json().ok()?;

    if !body.ok {
        return None;
    }

    body.result
        .and_then(|r| r.function)
        .and_then(|mut f| f.remove(selector))
        .and_then(|entries| entries.into_iter().next())
        .map(|e| e.name)
}

/// Look up a function signature on 4byte.directory.
async fn lookup_4byte(selector: &str, http_client: &dyn crate::http::HttpClient) -> Option<String> {
    let hex = selector.trim_start_matches("0x");
    let url = format!(
        "https://www.4byte.directory/api/v1/signatures/?hex_signature=0x{}",
        hex
    );

    let response = http_client
        .send(crate::http::Request::get(&url))
        .await
        .ok()?;
    let body: FourByteResponse = response.json().ok()?;
    body.results.into_iter().next().map(|r| r.text_signature)
}

/// Find an ABI entry matching a 4-byte selector.
fn find_abi_by_selector<'a>(selector: &str, abi: &'a [AbiEntry]) -> Option<&'a AbiEntry> {
    let selector_lower = selector.to_lowercase();
    abi.iter().find(|entry| {
        entry.entry_type == "function" && entry.selector().to_lowercase() == selector_lower
    })
}

/// Decode calldata parameters using ABI type information.
///
/// This performs basic hex-to-value decoding for common Solidity types.
/// For complex types (dynamic arrays, nested tuples), returns hex representation.
fn decode_params_from_abi(input: &str, entry: &AbiEntry) -> Vec<DecodedParam> {
    let data = if input.len() > 10 { &input[10..] } else { "" };

    entry
        .inputs
        .iter()
        .enumerate()
        .map(|(i, param)| {
            let offset = i * 64;
            let raw_value = if offset + 64 <= data.len() {
                &data[offset..offset + 64]
            } else if offset < data.len() {
                &data[offset..]
            } else {
                ""
            };

            let value = decode_abi_value(raw_value, &param.param_type);

            DecodedParam {
                name: if param.name.is_empty() {
                    format!("arg{}", i)
                } else {
                    param.name.clone()
                },
                param_type: param.param_type.clone(),
                value,
            }
        })
        .collect()
}

/// Decode a single ABI-encoded value from hex.
fn decode_abi_value(hex_value: &str, solidity_type: &str) -> String {
    if hex_value.is_empty() {
        return "(empty)".to_string();
    }

    match solidity_type {
        "address" => {
            // Address is right-padded in 32 bytes, take last 40 chars
            let addr = if hex_value.len() >= 40 {
                &hex_value[hex_value.len() - 40..]
            } else {
                hex_value
            };
            format!("0x{}", addr)
        }
        t if t.starts_with("uint") || t.starts_with("int") => {
            // Parse as big number (show decimal for reasonable values)
            let trimmed = hex_value.trim_start_matches('0');
            if trimmed.is_empty() {
                "0".to_string()
            } else if trimmed.len() <= 16 {
                // Fits in u64
                u64::from_str_radix(trimmed, 16)
                    .map(|v| v.to_string())
                    .unwrap_or_else(|_| format!("0x{}", hex_value))
            } else {
                format!("0x{}", trimmed)
            }
        }
        "bool" => {
            let last_char = hex_value.chars().last().unwrap_or('0');
            if last_char == '1' {
                "true".to_string()
            } else {
                "false".to_string()
            }
        }
        t if t.starts_with("bytes") && !t.contains('[') => {
            // Fixed-size bytes
            let n: usize = t.trim_start_matches("bytes").parse().unwrap_or(32);
            let hex_chars = n * 2;
            let bytes_hex = if hex_value.len() >= hex_chars {
                &hex_value[..hex_chars]
            } else {
                hex_value
            };
            format!("0x{}", bytes_hex)
        }
        _ => {
            // Dynamic types (string, bytes, arrays): show truncated hex
            if hex_value.len() > 16 {
                format!("0x{}...", &hex_value[..16])
            } else {
                format!("0x{}", hex_value)
            }
        }
    }
}

/// Build a selector-to-signature map from a contract's parsed ABI.
pub fn build_selector_map(abi: &[AbiEntry]) -> std::collections::HashMap<String, String> {
    abi.iter()
        .filter(|e| e.entry_type == "function")
        .map(|e| (e.selector().to_lowercase(), e.signature()))
        .collect()
}

/// Get all state-changing functions from an ABI.
pub fn get_state_changing_functions(abi: &[AbiEntry]) -> Vec<&AbiEntry> {
    abi.iter().filter(|e| e.is_state_changing()).collect()
}

/// Get all events from an ABI.
pub fn get_events(abi: &[AbiEntry]) -> Vec<&AbiEntry> {
    abi.iter().filter(|e| e.entry_type == "event").collect()
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::contract::source::AbiParam;

    #[test]
    fn test_decode_address() {
        let hex = "000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7";
        let result = decode_abi_value(hex, "address");
        assert_eq!(result, "0xdac17f958d2ee523a2206206994597c13d831ec7");
    }

    #[test]
    fn test_decode_uint256() {
        let hex = "0000000000000000000000000000000000000000000000000000000005f5e100";
        let result = decode_abi_value(hex, "uint256");
        assert_eq!(result, "100000000");
    }

    #[test]
    fn test_decode_uint256_zero() {
        let hex = "0000000000000000000000000000000000000000000000000000000000000000";
        let result = decode_abi_value(hex, "uint256");
        assert_eq!(result, "0");
    }

    #[test]
    fn test_decode_bool_true() {
        let hex = "0000000000000000000000000000000000000000000000000000000000000001";
        let result = decode_abi_value(hex, "bool");
        assert_eq!(result, "true");
    }

    #[test]
    fn test_decode_bool_false() {
        let hex = "0000000000000000000000000000000000000000000000000000000000000000";
        let result = decode_abi_value(hex, "bool");
        assert_eq!(result, "false");
    }

    #[test]
    fn test_decode_empty() {
        let result = decode_abi_value("", "uint256");
        assert_eq!(result, "(empty)");
    }

    #[test]
    fn test_native_transfer_decoding() {
        let rt = tokio::runtime::Runtime::new().unwrap();
        let result = rt.block_on(async {
            let client = crate::http::NativeHttpClient::new().unwrap();
            decode_calldata("0x", None, &client).await
        });
        assert_eq!(result.function_name, "Native Transfer");
    }

    #[test]
    fn test_build_selector_map() {
        let abi = vec![
            AbiEntry {
                entry_type: "function".to_string(),
                name: "transfer".to_string(),
                inputs: vec![
                    AbiParam {
                        name: "to".to_string(),
                        param_type: "address".to_string(),
                        indexed: false,
                        components: vec![],
                    },
                    AbiParam {
                        name: "amount".to_string(),
                        param_type: "uint256".to_string(),
                        indexed: false,
                        components: vec![],
                    },
                ],
                outputs: vec![],
                state_mutability: "nonpayable".to_string(),
            },
            AbiEntry {
                entry_type: "event".to_string(),
                name: "Transfer".to_string(),
                inputs: vec![],
                outputs: vec![],
                state_mutability: String::new(),
            },
        ];
        let map = build_selector_map(&abi);
        assert_eq!(map.len(), 1); // Only functions, not events
        assert!(map.values().any(|v| v == "transfer(address,uint256)"));
    }

    #[test]
    fn test_get_state_changing_functions() {
        let abi = vec![
            AbiEntry {
                entry_type: "function".to_string(),
                name: "transfer".to_string(),
                inputs: vec![],
                outputs: vec![],
                state_mutability: "nonpayable".to_string(),
            },
            AbiEntry {
                entry_type: "function".to_string(),
                name: "balanceOf".to_string(),
                inputs: vec![],
                outputs: vec![],
                state_mutability: "view".to_string(),
            },
        ];
        let sc_fns = get_state_changing_functions(&abi);
        assert_eq!(sc_fns.len(), 1);
        assert_eq!(sc_fns[0].name, "transfer");
    }

    #[test]
    fn test_get_events() {
        let abi = vec![
            AbiEntry {
                entry_type: "function".to_string(),
                name: "transfer".to_string(),
                inputs: vec![],
                outputs: vec![],
                state_mutability: "nonpayable".to_string(),
            },
            AbiEntry {
                entry_type: "event".to_string(),
                name: "Transfer".to_string(),
                inputs: vec![],
                outputs: vec![],
                state_mutability: String::new(),
            },
            AbiEntry {
                entry_type: "event".to_string(),
                name: "Approval".to_string(),
                inputs: vec![],
                outputs: vec![],
                state_mutability: String::new(),
            },
        ];
        let events = get_events(&abi);
        assert_eq!(events.len(), 2);
        assert_eq!(events[0].name, "Transfer");
        assert_eq!(events[1].name, "Approval");
    }

    #[test]
    fn test_find_abi_by_selector_match() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "transfer".to_string(),
            inputs: vec![
                AbiParam {
                    name: "to".to_string(),
                    param_type: "address".to_string(),
                    indexed: false,
                    components: vec![],
                },
                AbiParam {
                    name: "amount".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
            ],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let selector = entry.selector();
        let abi = vec![entry];
        let found = find_abi_by_selector(&selector, &abi);
        assert!(found.is_some());
        assert_eq!(found.unwrap().name, "transfer");
    }

    #[test]
    fn test_find_abi_by_selector_no_match() {
        let abi = vec![AbiEntry {
            entry_type: "function".to_string(),
            name: "transfer".to_string(),
            inputs: vec![],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        }];
        let found = find_abi_by_selector("0xdeadbeef", &abi);
        assert!(found.is_none());
    }

    #[test]
    fn test_find_abi_by_selector_skips_events() {
        let abi = vec![AbiEntry {
            entry_type: "event".to_string(),
            name: "Transfer".to_string(),
            inputs: vec![],
            outputs: vec![],
            state_mutability: String::new(),
        }];
        let found = find_abi_by_selector("0xdeadbeef", &abi);
        assert!(found.is_none());
    }

    #[test]
    fn test_decode_params_from_abi_basic() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "transfer".to_string(),
            inputs: vec![
                AbiParam {
                    name: "to".to_string(),
                    param_type: "address".to_string(),
                    indexed: false,
                    components: vec![],
                },
                AbiParam {
                    name: "amount".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
            ],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let selector = entry.selector();
        let addr_pad = "000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7";
        let amount_pad = "0000000000000000000000000000000000000000000000000000000005f5e100";
        let input = format!("{}{}{}", selector, addr_pad, amount_pad);
        let params = decode_params_from_abi(&input, &entry);
        assert_eq!(params.len(), 2);
        assert_eq!(params[0].name, "to");
        assert_eq!(params[0].param_type, "address");
        assert!(
            params[0]
                .value
                .contains("dac17f958d2ee523a2206206994597c13d831ec7")
        );
        assert_eq!(params[1].name, "amount");
        assert_eq!(params[1].value, "100000000");
    }

    #[test]
    fn test_decode_params_from_abi_unnamed_params() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "test".to_string(),
            inputs: vec![AbiParam {
                name: String::new(),
                param_type: "bool".to_string(),
                indexed: false,
                components: vec![],
            }],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let selector = entry.selector();
        let bool_pad = "0000000000000000000000000000000000000000000000000000000000000001";
        let input = format!("{}{}", selector, bool_pad);
        let params = decode_params_from_abi(&input, &entry);
        assert_eq!(params.len(), 1);
        assert_eq!(params[0].name, "arg0");
        assert_eq!(params[0].value, "true");
    }

    #[test]
    fn test_decode_params_from_abi_short_data() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "test".to_string(),
            inputs: vec![
                AbiParam {
                    name: "a".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
                AbiParam {
                    name: "b".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
            ],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let input = format!(
            "0xa1b2c3d4{}",
            "00000000000000000000000000000000000000000000000000000000000000ff00"
        );
        let params = decode_params_from_abi(&input, &entry);
        assert_eq!(params.len(), 2);
        assert_eq!(params[0].name, "a");
        assert!(!params[1].value.is_empty());
    }

    #[test]
    fn test_decode_params_no_data() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "test".to_string(),
            inputs: vec![AbiParam {
                name: "x".to_string(),
                param_type: "uint256".to_string(),
                indexed: false,
                components: vec![],
            }],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let input = "0xa1b2c3d4";
        let params = decode_params_from_abi(input, &entry);
        assert_eq!(params.len(), 1);
        assert_eq!(params[0].value, "(empty)");
    }

    #[test]
    fn test_decode_abi_value_int() {
        let hex = "0000000000000000000000000000000000000000000000000000000000000042";
        assert_eq!(decode_abi_value(hex, "int256"), "66");
    }

    #[test]
    fn test_decode_abi_value_large_uint() {
        let hex = "00000000000000000000000000000000ffffffffffffffffffffffffffffffff";
        let result = decode_abi_value(hex, "uint256");
        assert!(result.starts_with("0x"));
    }

    #[test]
    fn test_decode_abi_value_bytes4() {
        let hex = "a9059cbb00000000000000000000000000000000000000000000000000000000";
        let result = decode_abi_value(hex, "bytes4");
        assert_eq!(result, "0xa9059cbb");
    }

    #[test]
    fn test_decode_abi_value_bytes32() {
        let hex = "a9059cbb000000000000000000000000000000000000000000000000deadbeef";
        let result = decode_abi_value(hex, "bytes32");
        assert!(result.starts_with("0x"));
        assert_eq!(result.len(), 2 + 64);
    }

    #[test]
    fn test_decode_abi_value_short_address() {
        let hex = "deadbeef";
        let result = decode_abi_value(hex, "address");
        assert_eq!(result, "0xdeadbeef");
    }

    #[test]
    fn test_decode_abi_value_dynamic_type_long() {
        let hex = "0000000000000000000000000000000000000000000000000000000000000020";
        let result = decode_abi_value(hex, "string");
        assert!(result.starts_with("0x"));
        assert!(result.ends_with("..."));
    }

    #[test]
    fn test_decode_abi_value_dynamic_type_short() {
        let hex = "abcdef01";
        let result = decode_abi_value(hex, "bytes");
        assert_eq!(result, "0xabcdef01");
    }

    #[test]
    fn test_decode_calldata_empty_string() {
        let rt = tokio::runtime::Runtime::new().unwrap();
        let result = rt.block_on(async {
            let client = crate::http::NativeHttpClient::new().unwrap();
            decode_calldata("", None, &client).await
        });
        assert_eq!(result.function_name, "Native Transfer");
        assert_eq!(result.selector, "0x");
    }

    #[test]
    fn test_decode_calldata_short_selector() {
        let rt = tokio::runtime::Runtime::new().unwrap();
        let result = rt.block_on(async {
            let client = crate::http::NativeHttpClient::new().unwrap();
            decode_calldata("0xabcd", None, &client).await
        });
        assert_eq!(result.selector, "0xabcd");
    }

    #[test]
    fn test_decode_calldata_with_abi() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "transfer".to_string(),
            inputs: vec![
                AbiParam {
                    name: "to".to_string(),
                    param_type: "address".to_string(),
                    indexed: false,
                    components: vec![],
                },
                AbiParam {
                    name: "value".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
            ],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let selector = entry.selector();
        let source = ContractSource {
            contract_name: "Token".to_string(),
            source_code: String::new(),
            abi: String::new(),
            compiler_version: String::new(),
            optimization_used: false,
            optimization_runs: 0,
            evm_version: String::new(),
            license_type: String::new(),
            is_proxy: false,
            implementation_address: None,
            constructor_arguments: String::new(),
            library: String::new(),
            swarm_source: String::new(),
            parsed_abi: vec![entry],
        };
        let addr_pad = "000000000000000000000000dac17f958d2ee523a2206206994597c13d831ec7";
        let amt_pad = "0000000000000000000000000000000000000000000000000000000005f5e100";
        let input = format!("{}{}{}", selector, addr_pad, amt_pad);

        let rt = tokio::runtime::Runtime::new().unwrap();
        let result = rt.block_on(async {
            let client = crate::http::NativeHttpClient::new().unwrap();
            decode_calldata(&input, Some(&source), &client).await
        });
        assert_eq!(result.function_name, "transfer");
        assert_eq!(result.parameters.len(), 2);
        matches!(result.source, DecodeSource::VerifiedAbi);
    }

    #[test]
    fn test_decode_abi_value_uint_parse_error() {
        let hex = "zzzzzzzzzzzzzzzz";
        let result = decode_abi_value(hex, "uint256");
        assert!(result.starts_with("0x"));
    }

    #[test]
    fn test_decode_abi_value_bytes_without_size() {
        let hex = "a9059cbb00000000000000000000000000000000000000000000000000000000";
        let result = decode_abi_value(hex, "bytes");
        assert!(result.starts_with("0x"));
    }

    #[test]
    fn test_decode_abi_value_bool_non_one_zero() {
        let hex = "0000000000000000000000000000000000000000000000000000000000000002";
        let result = decode_abi_value(hex, "bool");
        assert_eq!(result, "false");
    }

    #[test]
    fn test_decode_params_from_abi_offset_exceeds_data() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "twoArgs".to_string(),
            inputs: vec![
                AbiParam {
                    name: "a".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
                AbiParam {
                    name: "b".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
            ],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let selector = entry.selector();
        let single_param_data = "0000000000000000000000000000000000000000000000000000000000000042";
        let input = format!("{}{}", selector, single_param_data);
        let params = decode_params_from_abi(&input, &entry);
        assert_eq!(params.len(), 2);
        assert_eq!(params[0].value, "66");
        assert_eq!(params[1].value, "(empty)");
    }

    #[test]
    fn test_decode_params_from_abi_partial_second_param() {
        let entry = AbiEntry {
            entry_type: "function".to_string(),
            name: "twoArgs".to_string(),
            inputs: vec![
                AbiParam {
                    name: "a".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
                AbiParam {
                    name: "b".to_string(),
                    param_type: "uint256".to_string(),
                    indexed: false,
                    components: vec![],
                },
            ],
            outputs: vec![],
            state_mutability: "nonpayable".to_string(),
        };
        let selector = entry.selector();
        let first_full = "0000000000000000000000000000000000000000000000000000000000000042";
        let second_partial = "000000000000000000000000000000000000000000000000000000000000";
        let input = format!("{}{}{}", selector, first_full, second_partial);
        let params = decode_params_from_abi(&input, &entry);
        assert_eq!(params.len(), 2);
        assert_eq!(params[0].value, "66");
    }

    #[test]
    fn test_decode_calldata_raw_selector_fallback() {
        let rt = tokio::runtime::Runtime::new().unwrap();
        let result = rt.block_on(async {
            let client = crate::http::NativeHttpClient::new().unwrap();
            decode_calldata("0xdeadbeef", None, &client).await
        });
        assert_eq!(result.selector, "0xdeadbeef");
        matches!(
            result.source,
            DecodeSource::Unknown | DecodeSource::FourByteDirectory
        );
    }

    #[test]
    fn test_decoded_call_serialize_deserialize() {
        let call = DecodedCall {
            selector: "0xa9059cbb".to_string(),
            signature: "transfer(address,uint256)".to_string(),
            function_name: "transfer".to_string(),
            parameters: vec![DecodedParam {
                name: "to".to_string(),
                param_type: "address".to_string(),
                value: "0xdac17f958d2ee523a2206206994597c13d831ec7".to_string(),
            }],
            source: DecodeSource::VerifiedAbi,
        };
        let json = serde_json::to_string(&call).unwrap();
        let restored: DecodedCall = serde_json::from_str(&json).unwrap();
        assert_eq!(restored.selector, call.selector);
        assert_eq!(restored.function_name, call.function_name);
        assert_eq!(restored.parameters.len(), 1);
    }
    /// Answers each request with the body of the first route whose URL
    /// fragment the request URL contains, and notes every URL. A URL no
    /// route matches is a transport error.
    struct Routes {
        routes: Vec<(&'static str, &'static str)>,
        urls: std::sync::Mutex<Vec<String>>,
    }

    impl Routes {
        fn new(routes: Vec<(&'static str, &'static str)>) -> Self {
            Self {
                routes,
                urls: Default::default(),
            }
        }
    }

    #[async_trait::async_trait]
    impl crate::http::HttpClient for Routes {
        async fn send(
            &self,
            req: crate::http::Request,
        ) -> std::result::Result<crate::http::Response, crate::error::ScopeError> {
            self.urls.lock().unwrap().push(req.url.clone());
            let (_, body) = self
                .routes
                .iter()
                .find(|(fragment, _)| req.url.contains(fragment))
                .ok_or_else(|| crate::error::ScopeError::Network("unreachable".into()))?;
            Ok(crate::http::Response {
                status_code: 200,
                headers: Default::default(),
                body: body.to_string(),
            })
        }
    }

    const OPENCHAIN: &str = "api.openchain.xyz";
    const FOURBYTE: &str = "4byte.directory";

    #[tokio::test]
    async fn test_decode_calldata_names_the_function_from_openchain() {
        let http = Routes::new(vec![(
            OPENCHAIN,
            r#"{"ok": true, "result": {"function": {"0xa9059cbb": [{"name": "transfer(address,uint256)"}, {"name": "other()"}]}}}"#,
        )]);
        let call = decode_calldata("0xa9059cbb000000", None, &http).await;
        assert_eq!(call.selector, "0xa9059cbb");
        assert_eq!(call.signature, "transfer(address,uint256)");
        assert_eq!(call.function_name, "transfer");
        assert!(call.parameters.is_empty());
        assert!(matches!(call.source, DecodeSource::FourByteDirectory));
        let urls = http.urls.lock().unwrap();
        assert_eq!(
            *urls,
            vec![
                "https://api.openchain.xyz/signature-database/v1/lookup?function=0xa9059cbb&filter=true"
            ],
            "4byte is not asked once OpenChain answers"
        );
    }

    #[tokio::test]
    async fn test_decode_calldata_falls_back_to_4byte_when_openchain_has_nothing() {
        for openchain in [
            r#"{"ok": false}"#,
            r#"{"ok": true, "result": {"function": {"0x095ea7b3": []}}}"#,
            r#"{"ok": true, "result": {"function": {"0xffffffff": [{"name": "x()"}]}}}"#,
            r#"{"ok": true, "result": null}"#,
            "not json",
        ] {
            let http = Routes::new(vec![
                (OPENCHAIN, openchain),
                (
                    FOURBYTE,
                    r#"{"results": [{"text_signature": "approve(address,uint256)"}]}"#,
                ),
            ]);
            let call = decode_calldata("0x095ea7b3", None, &http).await;
            assert_eq!(call.signature, "approve(address,uint256)", "{openchain}");
            assert_eq!(call.function_name, "approve");
            assert!(matches!(call.source, DecodeSource::FourByteDirectory));
            let urls = http.urls.lock().unwrap();
            assert_eq!(
                urls[1],
                "https://www.4byte.directory/api/v1/signatures/?hex_signature=0x095ea7b3"
            );
        }
    }

    #[tokio::test]
    async fn test_decode_calldata_without_any_lookup_shows_the_raw_selector() {
        for http in [
            Routes::new(vec![]),
            Routes::new(vec![
                (OPENCHAIN, r#"{"ok": false}"#),
                (FOURBYTE, r#"{"results": []}"#),
            ]),
        ] {
            let call = decode_calldata("0xdeadbeef01", None, &http).await;
            assert_eq!(call.selector, "0xdeadbeef");
            assert_eq!(call.signature, "0xdeadbeef(...)");
            assert_eq!(call.function_name, "0xdeadbeef");
            assert!(matches!(call.source, DecodeSource::Unknown));
            assert_eq!(http.urls.lock().unwrap().len(), 2);
        }
    }

    #[test]
    fn test_decode_abi_value_short_dynamic_type_is_shown_whole() {
        // "bytes" alone takes the fixed-size branch; "string" is dynamic.
        assert_eq!(decode_abi_value("abcdef01", "string"), "0xabcdef01");
        assert_eq!(decode_abi_value("abcdef01", "address[]"), "0xabcdef01");
    }
}