//! `SubTest` trait.

use anyhow::Context as _;
use cranelift_codegen::ir::Function;
use cranelift_codegen::isa::TargetIsa;
use cranelift_codegen::settings::{Flags, FlagsOrIsa};
use cranelift_reader::{Comment, Details};
use filecheck::{Checker, CheckerBuilder, NO_VARIABLES};
use std::borrow::Cow;

/// Context for running a test on a single function.
pub struct Context<'a> {
    /// Comments from the preamble f the test file. These apply to all functions.
    pub preamble_comments: &'a [Comment<'a>],

    /// Additional details about the function from the parser.
    pub details: Details<'a>,

    /// Was the function verified before running this test?
    pub verified: bool,

    /// ISA-independent flags for this test.
    pub flags: &'a Flags,

    /// Target ISA to test against. Only guaranteed to be present for sub-tests whose `needs_isa`
    /// method returned `true`. For other sub-tests, this is set if the test file has a unique ISA.
    pub isa: Option<&'a dyn TargetIsa>,

    /// Full path to the file containing the test.
    pub file_path: &'a str,
}

impl<'a> Context<'a> {
    /// Get a `FlagsOrIsa` object for passing to the verifier.
    pub fn flags_or_isa(&self) -> FlagsOrIsa<'a> {
        FlagsOrIsa {
            flags: self.flags,
            isa: self.isa,
        }
    }
}

/// Common interface for implementations of test commands.
///
/// Each `.clif` test file may contain multiple test commands, each represented by a `SubTest`
/// trait object.
pub trait SubTest {
    /// Name identifying this subtest. Typically the same as the test command.
    fn name(&self) -> &'static str;

    /// Should the verifier be run on the function before running the test?
    fn needs_verifier(&self) -> bool {
        true
    }

    /// Does this test mutate the function when it runs?
    /// This is used as a hint to avoid cloning the function needlessly.
    fn is_mutating(&self) -> bool {
        false
    }

    /// Does this test need a `TargetIsa` trait object?
    fn needs_isa(&self) -> bool {
        false
    }

    /// Run this test on `func`.
    fn run(&self, func: Cow<Function>, context: &Context) -> anyhow::Result<()>;
}

/// Run filecheck on `text`, using directives extracted from `context`.
pub fn run_filecheck(text: &str, context: &Context) -> anyhow::Result<()> {
    let checker = build_filechecker(context)?;
    if checker
        .check(text, NO_VARIABLES)
        .context("filecheck failed")?
    {
        Ok(())
    } else {
        // Filecheck mismatch. Emit an explanation as output.
        let (_, explain) = checker
            .explain(text, NO_VARIABLES)
            .context("filecheck explain failed")?;
        anyhow::bail!("filecheck failed:\n{}{}", checker, explain);
    }
}

/// Build a filechecker using the directives in the file preamble and the function's comments.
pub fn build_filechecker(context: &Context) -> anyhow::Result<Checker> {
    let mut builder = CheckerBuilder::new();
    // Preamble comments apply to all functions.
    for comment in context.preamble_comments {
        builder
            .directive(comment.text)
            .context("filecheck directive failed")?;
    }
    for comment in &context.details.comments {
        builder
            .directive(comment.text)
            .context("filecheck directive failed")?;
    }
    Ok(builder.finish())
}